Source file src/cmd/api/main_test.go

Documentation: cmd/api

     1  // Copyright 2011 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  // This package computes the exported API of a set of Go packages.
     6  // It is only a test, not a command, nor a usefully importable package.
     7  
     8  package main
     9  
    10  import (
    11  	"bufio"
    12  	"bytes"
    13  	"encoding/json"
    14  	"fmt"
    15  	"go/ast"
    16  	"go/build"
    17  	"go/parser"
    18  	"go/token"
    19  	"go/types"
    20  	"internal/testenv"
    21  	"io"
    22  	"log"
    23  	"os"
    24  	"os/exec"
    25  	"path/filepath"
    26  	"regexp"
    27  	"runtime"
    28  	"sort"
    29  	"strconv"
    30  	"strings"
    31  	"sync"
    32  	"testing"
    33  )
    34  
    35  const verbose = false
    36  
    37  func goCmd() string {
    38  	var exeSuffix string
    39  	if runtime.GOOS == "windows" {
    40  		exeSuffix = ".exe"
    41  	}
    42  	path := filepath.Join(testenv.GOROOT(nil), "bin", "go"+exeSuffix)
    43  	if _, err := os.Stat(path); err == nil {
    44  		return path
    45  	}
    46  	return "go"
    47  }
    48  
    49  // contexts are the default contexts which are scanned.
    50  var contexts = []*build.Context{
    51  	{GOOS: "linux", GOARCH: "386", CgoEnabled: true},
    52  	{GOOS: "linux", GOARCH: "386"},
    53  	{GOOS: "linux", GOARCH: "amd64", CgoEnabled: true},
    54  	{GOOS: "linux", GOARCH: "amd64"},
    55  	{GOOS: "linux", GOARCH: "arm", CgoEnabled: true},
    56  	{GOOS: "linux", GOARCH: "arm"},
    57  	{GOOS: "darwin", GOARCH: "amd64", CgoEnabled: true},
    58  	{GOOS: "darwin", GOARCH: "amd64"},
    59  	{GOOS: "darwin", GOARCH: "arm64", CgoEnabled: true},
    60  	{GOOS: "darwin", GOARCH: "arm64"},
    61  	{GOOS: "windows", GOARCH: "amd64"},
    62  	{GOOS: "windows", GOARCH: "386"},
    63  	{GOOS: "freebsd", GOARCH: "386", CgoEnabled: true},
    64  	{GOOS: "freebsd", GOARCH: "386"},
    65  	{GOOS: "freebsd", GOARCH: "amd64", CgoEnabled: true},
    66  	{GOOS: "freebsd", GOARCH: "amd64"},
    67  	{GOOS: "freebsd", GOARCH: "arm", CgoEnabled: true},
    68  	{GOOS: "freebsd", GOARCH: "arm"},
    69  	{GOOS: "freebsd", GOARCH: "arm64", CgoEnabled: true},
    70  	{GOOS: "freebsd", GOARCH: "arm64"},
    71  	{GOOS: "freebsd", GOARCH: "riscv64", CgoEnabled: true},
    72  	{GOOS: "freebsd", GOARCH: "riscv64"},
    73  	{GOOS: "netbsd", GOARCH: "386", CgoEnabled: true},
    74  	{GOOS: "netbsd", GOARCH: "386"},
    75  	{GOOS: "netbsd", GOARCH: "amd64", CgoEnabled: true},
    76  	{GOOS: "netbsd", GOARCH: "amd64"},
    77  	{GOOS: "netbsd", GOARCH: "arm", CgoEnabled: true},
    78  	{GOOS: "netbsd", GOARCH: "arm"},
    79  	{GOOS: "netbsd", GOARCH: "arm64", CgoEnabled: true},
    80  	{GOOS: "netbsd", GOARCH: "arm64"},
    81  	{GOOS: "openbsd", GOARCH: "386", CgoEnabled: true},
    82  	{GOOS: "openbsd", GOARCH: "386"},
    83  	{GOOS: "openbsd", GOARCH: "amd64", CgoEnabled: true},
    84  	{GOOS: "openbsd", GOARCH: "amd64"},
    85  }
    86  
    87  func contextName(c *build.Context) string {
    88  	s := c.GOOS + "-" + c.GOARCH
    89  	if c.CgoEnabled {
    90  		s += "-cgo"
    91  	}
    92  	if c.Dir != "" {
    93  		s += fmt.Sprintf(" [%s]", c.Dir)
    94  	}
    95  	return s
    96  }
    97  
    98  var internalPkg = regexp.MustCompile(`(^|/)internal($|/)`)
    99  
   100  var exitCode = 0
   101  
   102  func Check(t *testing.T) {
   103  	checkFiles, err := filepath.Glob(filepath.Join(testenv.GOROOT(t), "api/go1*.txt"))
   104  	if err != nil {
   105  		t.Fatal(err)
   106  	}
   107  
   108  	var nextFiles []string
   109  	if v := runtime.Version(); strings.Contains(v, "devel") || strings.Contains(v, "beta") {
   110  		next, err := filepath.Glob(filepath.Join(testenv.GOROOT(t), "api/next/*.txt"))
   111  		if err != nil {
   112  			t.Fatal(err)
   113  		}
   114  		nextFiles = next
   115  	}
   116  
   117  	for _, c := range contexts {
   118  		c.Compiler = build.Default.Compiler
   119  	}
   120  
   121  	walkers := make([]*Walker, len(contexts))
   122  	var wg sync.WaitGroup
   123  	for i, context := range contexts {
   124  		i, context := i, context
   125  		wg.Add(1)
   126  		go func() {
   127  			defer wg.Done()
   128  			walkers[i] = NewWalker(context, filepath.Join(testenv.GOROOT(t), "src"))
   129  		}()
   130  	}
   131  	wg.Wait()
   132  
   133  	var featureCtx = make(map[string]map[string]bool) // feature -> context name -> true
   134  	for _, w := range walkers {
   135  		for _, name := range w.stdPackages {
   136  			pkg, err := w.import_(name)
   137  			if _, nogo := err.(*build.NoGoError); nogo {
   138  				continue
   139  			}
   140  			if err != nil {
   141  				log.Fatalf("Import(%q): %v", name, err)
   142  			}
   143  			w.export(pkg)
   144  		}
   145  
   146  		ctxName := contextName(w.context)
   147  		for _, f := range w.Features() {
   148  			if featureCtx[f] == nil {
   149  				featureCtx[f] = make(map[string]bool)
   150  			}
   151  			featureCtx[f][ctxName] = true
   152  		}
   153  	}
   154  
   155  	var features []string
   156  	for f, cmap := range featureCtx {
   157  		if len(cmap) == len(contexts) {
   158  			features = append(features, f)
   159  			continue
   160  		}
   161  		comma := strings.Index(f, ",")
   162  		for cname := range cmap {
   163  			f2 := fmt.Sprintf("%s (%s)%s", f[:comma], cname, f[comma:])
   164  			features = append(features, f2)
   165  		}
   166  	}
   167  
   168  	bw := bufio.NewWriter(os.Stdout)
   169  	defer bw.Flush()
   170  
   171  	var required []string
   172  	for _, file := range checkFiles {
   173  		required = append(required, fileFeatures(file, needApproval(file))...)
   174  	}
   175  	for _, file := range nextFiles {
   176  		required = append(required, fileFeatures(file, true)...)
   177  	}
   178  	exception := fileFeatures(filepath.Join(testenv.GOROOT(t), "api/except.txt"), false)
   179  
   180  	if exitCode == 1 {
   181  		t.Errorf("API database problems found")
   182  	}
   183  	if !compareAPI(bw, features, required, exception) {
   184  		t.Errorf("API differences found")
   185  	}
   186  }
   187  
   188  // export emits the exported package features.
   189  func (w *Walker) export(pkg *apiPackage) {
   190  	if verbose {
   191  		log.Println(pkg)
   192  	}
   193  	pop := w.pushScope("pkg " + pkg.Path())
   194  	w.current = pkg
   195  	w.collectDeprecated()
   196  	scope := pkg.Scope()
   197  	for _, name := range scope.Names() {
   198  		if token.IsExported(name) {
   199  			w.emitObj(scope.Lookup(name))
   200  		}
   201  	}
   202  	pop()
   203  }
   204  
   205  func set(items []string) map[string]bool {
   206  	s := make(map[string]bool)
   207  	for _, v := range items {
   208  		s[v] = true
   209  	}
   210  	return s
   211  }
   212  
   213  var spaceParensRx = regexp.MustCompile(` \(\S+?\)`)
   214  
   215  func featureWithoutContext(f string) string {
   216  	if !strings.Contains(f, "(") {
   217  		return f
   218  	}
   219  	return spaceParensRx.ReplaceAllString(f, "")
   220  }
   221  
   222  // portRemoved reports whether the given port-specific API feature is
   223  // okay to no longer exist because its port was removed.
   224  func portRemoved(feature string) bool {
   225  	return strings.Contains(feature, "(darwin-386)") ||
   226  		strings.Contains(feature, "(darwin-386-cgo)")
   227  }
   228  
   229  func compareAPI(w io.Writer, features, required, exception []string) (ok bool) {
   230  	ok = true
   231  
   232  	featureSet := set(features)
   233  	exceptionSet := set(exception)
   234  
   235  	sort.Strings(features)
   236  	sort.Strings(required)
   237  
   238  	take := func(sl *[]string) string {
   239  		s := (*sl)[0]
   240  		*sl = (*sl)[1:]
   241  		return s
   242  	}
   243  
   244  	for len(features) > 0 || len(required) > 0 {
   245  		switch {
   246  		case len(features) == 0 || (len(required) > 0 && required[0] < features[0]):
   247  			feature := take(&required)
   248  			if exceptionSet[feature] {
   249  				// An "unfortunate" case: the feature was once
   250  				// included in the API (e.g. go1.txt), but was
   251  				// subsequently removed. These are already
   252  				// acknowledged by being in the file
   253  				// "api/except.txt". No need to print them out
   254  				// here.
   255  			} else if portRemoved(feature) {
   256  				// okay.
   257  			} else if featureSet[featureWithoutContext(feature)] {
   258  				// okay.
   259  			} else {
   260  				fmt.Fprintf(w, "-%s\n", feature)
   261  				ok = false // broke compatibility
   262  			}
   263  		case len(required) == 0 || (len(features) > 0 && required[0] > features[0]):
   264  			newFeature := take(&features)
   265  			fmt.Fprintf(w, "+%s\n", newFeature)
   266  			ok = false // feature not in api/next/*
   267  		default:
   268  			take(&required)
   269  			take(&features)
   270  		}
   271  	}
   272  
   273  	return ok
   274  }
   275  
   276  // aliasReplacer applies type aliases to earlier API files,
   277  // to avoid misleading negative results.
   278  // This makes all the references to os.FileInfo in go1.txt
   279  // be read as if they said fs.FileInfo, since os.FileInfo is now an alias.
   280  // If there are many of these, we could do a more general solution,
   281  // but for now the replacer is fine.
   282  var aliasReplacer = strings.NewReplacer(
   283  	"os.FileInfo", "fs.FileInfo",
   284  	"os.FileMode", "fs.FileMode",
   285  	"os.PathError", "fs.PathError",
   286  )
   287  
   288  func fileFeatures(filename string, needApproval bool) []string {
   289  	bs, err := os.ReadFile(filename)
   290  	if err != nil {
   291  		log.Fatal(err)
   292  	}
   293  	s := string(bs)
   294  
   295  	// Diagnose common mistakes people make,
   296  	// since there is no apifmt to format these files.
   297  	// The missing final newline is important for the
   298  	// final release step of cat next/*.txt >go1.X.txt.
   299  	// If the files don't end in full lines, the concatenation goes awry.
   300  	if strings.Contains(s, "\r") {
   301  		log.Printf("%s: contains CRLFs", filename)
   302  		exitCode = 1
   303  	}
   304  	if filepath.Base(filename) == "go1.4.txt" {
   305  		// No use for blank lines in api files, except go1.4.txt
   306  		// used them in a reasonable way and we should let it be.
   307  	} else if strings.HasPrefix(s, "\n") || strings.Contains(s, "\n\n") {
   308  		log.Printf("%s: contains a blank line", filename)
   309  		exitCode = 1
   310  	}
   311  	if s == "" {
   312  		log.Printf("%s: empty file", filename)
   313  		exitCode = 1
   314  	} else if s[len(s)-1] != '\n' {
   315  		log.Printf("%s: missing final newline", filename)
   316  		exitCode = 1
   317  	}
   318  	s = aliasReplacer.Replace(s)
   319  	lines := strings.Split(s, "\n")
   320  	var nonblank []string
   321  	for i, line := range lines {
   322  		line = strings.TrimSpace(line)
   323  		if line == "" || strings.HasPrefix(line, "#") {
   324  			continue
   325  		}
   326  		if needApproval {
   327  			feature, approval, ok := strings.Cut(line, "#")
   328  			if !ok {
   329  				log.Printf("%s:%d: missing proposal approval\n", filename, i+1)
   330  				exitCode = 1
   331  			} else {
   332  				_, err := strconv.Atoi(approval)
   333  				if err != nil {
   334  					log.Printf("%s:%d: malformed proposal approval #%s\n", filename, i+1, approval)
   335  					exitCode = 1
   336  				}
   337  			}
   338  			line = strings.TrimSpace(feature)
   339  		} else {
   340  			if strings.Contains(line, " #") {
   341  				log.Printf("%s:%d: unexpected approval\n", filename, i+1)
   342  				exitCode = 1
   343  			}
   344  		}
   345  		nonblank = append(nonblank, line)
   346  	}
   347  	return nonblank
   348  }
   349  
   350  var fset = token.NewFileSet()
   351  
   352  type Walker struct {
   353  	context     *build.Context
   354  	root        string
   355  	scope       []string
   356  	current     *apiPackage
   357  	deprecated  map[token.Pos]bool
   358  	features    map[string]bool              // set
   359  	imported    map[string]*apiPackage       // packages already imported
   360  	stdPackages []string                     // names, omitting "unsafe", internal, and vendored packages
   361  	importMap   map[string]map[string]string // importer dir -> import path -> canonical path
   362  	importDir   map[string]string            // canonical import path -> dir
   363  
   364  }
   365  
   366  func NewWalker(context *build.Context, root string) *Walker {
   367  	w := &Walker{
   368  		context:  context,
   369  		root:     root,
   370  		features: map[string]bool{},
   371  		imported: map[string]*apiPackage{"unsafe": &apiPackage{Package: types.Unsafe}},
   372  	}
   373  	w.loadImports()
   374  	return w
   375  }
   376  
   377  func (w *Walker) Features() (fs []string) {
   378  	for f := range w.features {
   379  		fs = append(fs, f)
   380  	}
   381  	sort.Strings(fs)
   382  	return
   383  }
   384  
   385  var parsedFileCache = make(map[string]*ast.File)
   386  
   387  func (w *Walker) parseFile(dir, file string) (*ast.File, error) {
   388  	filename := filepath.Join(dir, file)
   389  	if f := parsedFileCache[filename]; f != nil {
   390  		return f, nil
   391  	}
   392  
   393  	f, err := parser.ParseFile(fset, filename, nil, parser.ParseComments)
   394  	if err != nil {
   395  		return nil, err
   396  	}
   397  	parsedFileCache[filename] = f
   398  
   399  	return f, nil
   400  }
   401  
   402  // Disable before debugging non-obvious errors from the type-checker.
   403  const usePkgCache = true
   404  
   405  var (
   406  	pkgCache = map[string]*apiPackage{} // map tagKey to package
   407  	pkgTags  = map[string][]string{}    // map import dir to list of relevant tags
   408  )
   409  
   410  // tagKey returns the tag-based key to use in the pkgCache.
   411  // It is a comma-separated string; the first part is dir, the rest tags.
   412  // The satisfied tags are derived from context but only those that
   413  // matter (the ones listed in the tags argument plus GOOS and GOARCH) are used.
   414  // The tags list, which came from go/build's Package.AllTags,
   415  // is known to be sorted.
   416  func tagKey(dir string, context *build.Context, tags []string) string {
   417  	ctags := map[string]bool{
   418  		context.GOOS:   true,
   419  		context.GOARCH: true,
   420  	}
   421  	if context.CgoEnabled {
   422  		ctags["cgo"] = true
   423  	}
   424  	for _, tag := range context.BuildTags {
   425  		ctags[tag] = true
   426  	}
   427  	// TODO: ReleaseTags (need to load default)
   428  	key := dir
   429  
   430  	// explicit on GOOS and GOARCH as global cache will use "all" cached packages for
   431  	// an indirect imported package. See https://github.com/golang/go/issues/21181
   432  	// for more detail.
   433  	tags = append(tags, context.GOOS, context.GOARCH)
   434  	sort.Strings(tags)
   435  
   436  	for _, tag := range tags {
   437  		if ctags[tag] {
   438  			key += "," + tag
   439  			ctags[tag] = false
   440  		}
   441  	}
   442  	return key
   443  }
   444  
   445  type listImports struct {
   446  	stdPackages []string                     // names, omitting "unsafe", internal, and vendored packages
   447  	importDir   map[string]string            // canonical import path → directory
   448  	importMap   map[string]map[string]string // import path → canonical import path
   449  }
   450  
   451  var listCache sync.Map // map[string]listImports, keyed by contextName
   452  
   453  // listSem is a semaphore restricting concurrent invocations of 'go list'. 'go
   454  // list' has its own internal concurrency, so we use a hard-coded constant (to
   455  // allow the I/O-intensive phases of 'go list' to overlap) instead of scaling
   456  // all the way up to GOMAXPROCS.
   457  var listSem = make(chan semToken, 2)
   458  
   459  type semToken struct{}
   460  
   461  // loadImports populates w with information about the packages in the standard
   462  // library and the packages they themselves import in w's build context.
   463  //
   464  // The source import path and expanded import path are identical except for vendored packages.
   465  // For example, on return:
   466  //
   467  //	w.importMap["math"] = "math"
   468  //	w.importDir["math"] = "<goroot>/src/math"
   469  //
   470  //	w.importMap["golang.org/x/net/route"] = "vendor/golang.org/x/net/route"
   471  //	w.importDir["vendor/golang.org/x/net/route"] = "<goroot>/src/vendor/golang.org/x/net/route"
   472  //
   473  // Since the set of packages that exist depends on context, the result of
   474  // loadImports also depends on context. However, to improve test running time
   475  // the configuration for each environment is cached across runs.
   476  func (w *Walker) loadImports() {
   477  	if w.context == nil {
   478  		return // test-only Walker; does not use the import map
   479  	}
   480  
   481  	name := contextName(w.context)
   482  
   483  	imports, ok := listCache.Load(name)
   484  	if !ok {
   485  		listSem <- semToken{}
   486  		defer func() { <-listSem }()
   487  
   488  		cmd := exec.Command(goCmd(), "list", "-e", "-deps", "-json", "std")
   489  		cmd.Env = listEnv(w.context)
   490  		if w.context.Dir != "" {
   491  			cmd.Dir = w.context.Dir
   492  		}
   493  		cmd.Stderr = os.Stderr
   494  		out, err := cmd.Output()
   495  		if err != nil {
   496  			log.Fatalf("loading imports: %v\n%s", err, out)
   497  		}
   498  
   499  		var stdPackages []string
   500  		importMap := make(map[string]map[string]string)
   501  		importDir := make(map[string]string)
   502  		dec := json.NewDecoder(bytes.NewReader(out))
   503  		for {
   504  			var pkg struct {
   505  				ImportPath, Dir string
   506  				ImportMap       map[string]string
   507  				Standard        bool
   508  			}
   509  			err := dec.Decode(&pkg)
   510  			if err == io.EOF {
   511  				break
   512  			}
   513  			if err != nil {
   514  				log.Fatalf("go list: invalid output: %v", err)
   515  			}
   516  
   517  			// - Package "unsafe" contains special signatures requiring
   518  			//   extra care when printing them - ignore since it is not
   519  			//   going to change w/o a language change.
   520  			// - Internal and vendored packages do not contribute to our
   521  			//   API surface. (If we are running within the "std" module,
   522  			//   vendored dependencies appear as themselves instead of
   523  			//   their "vendor/" standard-library copies.)
   524  			// - 'go list std' does not include commands, which cannot be
   525  			//   imported anyway.
   526  			if ip := pkg.ImportPath; pkg.Standard && ip != "unsafe" && !strings.HasPrefix(ip, "vendor/") && !internalPkg.MatchString(ip) {
   527  				stdPackages = append(stdPackages, ip)
   528  			}
   529  			importDir[pkg.ImportPath] = pkg.Dir
   530  			if len(pkg.ImportMap) > 0 {
   531  				importMap[pkg.Dir] = make(map[string]string, len(pkg.ImportMap))
   532  			}
   533  			for k, v := range pkg.ImportMap {
   534  				importMap[pkg.Dir][k] = v
   535  			}
   536  		}
   537  
   538  		sort.Strings(stdPackages)
   539  		imports = listImports{
   540  			stdPackages: stdPackages,
   541  			importMap:   importMap,
   542  			importDir:   importDir,
   543  		}
   544  		imports, _ = listCache.LoadOrStore(name, imports)
   545  	}
   546  
   547  	li := imports.(listImports)
   548  	w.stdPackages = li.stdPackages
   549  	w.importDir = li.importDir
   550  	w.importMap = li.importMap
   551  }
   552  
   553  // listEnv returns the process environment to use when invoking 'go list' for
   554  // the given context.
   555  func listEnv(c *build.Context) []string {
   556  	if c == nil {
   557  		return os.Environ()
   558  	}
   559  
   560  	environ := append(os.Environ(),
   561  		"GOOS="+c.GOOS,
   562  		"GOARCH="+c.GOARCH)
   563  	if c.CgoEnabled {
   564  		environ = append(environ, "CGO_ENABLED=1")
   565  	} else {
   566  		environ = append(environ, "CGO_ENABLED=0")
   567  	}
   568  	return environ
   569  }
   570  
   571  type apiPackage struct {
   572  	*types.Package
   573  	Files []*ast.File
   574  }
   575  
   576  // Importing is a sentinel taking the place in Walker.imported
   577  // for a package that is in the process of being imported.
   578  var importing apiPackage
   579  
   580  // Import implements types.Importer.
   581  func (w *Walker) Import(name string) (*types.Package, error) {
   582  	return w.ImportFrom(name, "", 0)
   583  }
   584  
   585  // ImportFrom implements types.ImporterFrom.
   586  func (w *Walker) ImportFrom(fromPath, fromDir string, mode types.ImportMode) (*types.Package, error) {
   587  	pkg, err := w.importFrom(fromPath, fromDir, mode)
   588  	if err != nil {
   589  		return nil, err
   590  	}
   591  	return pkg.Package, nil
   592  }
   593  
   594  func (w *Walker) import_(name string) (*apiPackage, error) {
   595  	return w.importFrom(name, "", 0)
   596  }
   597  
   598  func (w *Walker) importFrom(fromPath, fromDir string, mode types.ImportMode) (*apiPackage, error) {
   599  	name := fromPath
   600  	if canonical, ok := w.importMap[fromDir][fromPath]; ok {
   601  		name = canonical
   602  	}
   603  
   604  	pkg := w.imported[name]
   605  	if pkg != nil {
   606  		if pkg == &importing {
   607  			log.Fatalf("cycle importing package %q", name)
   608  		}
   609  		return pkg, nil
   610  	}
   611  	w.imported[name] = &importing
   612  
   613  	// Determine package files.
   614  	dir := w.importDir[name]
   615  	if dir == "" {
   616  		dir = filepath.Join(w.root, filepath.FromSlash(name))
   617  	}
   618  	if fi, err := os.Stat(dir); err != nil || !fi.IsDir() {
   619  		log.Panicf("no source in tree for import %q (from import %s in %s): %v", name, fromPath, fromDir, err)
   620  	}
   621  
   622  	context := w.context
   623  	if context == nil {
   624  		context = &build.Default
   625  	}
   626  
   627  	// Look in cache.
   628  	// If we've already done an import with the same set
   629  	// of relevant tags, reuse the result.
   630  	var key string
   631  	if usePkgCache {
   632  		if tags, ok := pkgTags[dir]; ok {
   633  			key = tagKey(dir, context, tags)
   634  			if pkg := pkgCache[key]; pkg != nil {
   635  				w.imported[name] = pkg
   636  				return pkg, nil
   637  			}
   638  		}
   639  	}
   640  
   641  	info, err := context.ImportDir(dir, 0)
   642  	if err != nil {
   643  		if _, nogo := err.(*build.NoGoError); nogo {
   644  			return nil, err
   645  		}
   646  		log.Fatalf("pkg %q, dir %q: ScanDir: %v", name, dir, err)
   647  	}
   648  
   649  	// Save tags list first time we see a directory.
   650  	if usePkgCache {
   651  		if _, ok := pkgTags[dir]; !ok {
   652  			pkgTags[dir] = info.AllTags
   653  			key = tagKey(dir, context, info.AllTags)
   654  		}
   655  	}
   656  
   657  	filenames := append(append([]string{}, info.GoFiles...), info.CgoFiles...)
   658  
   659  	// Parse package files.
   660  	var files []*ast.File
   661  	for _, file := range filenames {
   662  		f, err := w.parseFile(dir, file)
   663  		if err != nil {
   664  			log.Fatalf("error parsing package %s: %s", name, err)
   665  		}
   666  		files = append(files, f)
   667  	}
   668  
   669  	// Type-check package files.
   670  	var sizes types.Sizes
   671  	if w.context != nil {
   672  		sizes = types.SizesFor(w.context.Compiler, w.context.GOARCH)
   673  	}
   674  	conf := types.Config{
   675  		IgnoreFuncBodies: true,
   676  		FakeImportC:      true,
   677  		Importer:         w,
   678  		Sizes:            sizes,
   679  	}
   680  	tpkg, err := conf.Check(name, fset, files, nil)
   681  	if err != nil {
   682  		ctxt := "<no context>"
   683  		if w.context != nil {
   684  			ctxt = fmt.Sprintf("%s-%s", w.context.GOOS, w.context.GOARCH)
   685  		}
   686  		log.Fatalf("error typechecking package %s: %s (%s)", name, err, ctxt)
   687  	}
   688  	pkg = &apiPackage{tpkg, files}
   689  
   690  	if usePkgCache {
   691  		pkgCache[key] = pkg
   692  	}
   693  
   694  	w.imported[name] = pkg
   695  	return pkg, nil
   696  }
   697  
   698  // pushScope enters a new scope (walking a package, type, node, etc)
   699  // and returns a function that will leave the scope (with sanity checking
   700  // for mismatched pushes & pops)
   701  func (w *Walker) pushScope(name string) (popFunc func()) {
   702  	w.scope = append(w.scope, name)
   703  	return func() {
   704  		if len(w.scope) == 0 {
   705  			log.Fatalf("attempt to leave scope %q with empty scope list", name)
   706  		}
   707  		if w.scope[len(w.scope)-1] != name {
   708  			log.Fatalf("attempt to leave scope %q, but scope is currently %#v", name, w.scope)
   709  		}
   710  		w.scope = w.scope[:len(w.scope)-1]
   711  	}
   712  }
   713  
   714  func sortedMethodNames(typ *types.Interface) []string {
   715  	n := typ.NumMethods()
   716  	list := make([]string, n)
   717  	for i := range list {
   718  		list[i] = typ.Method(i).Name()
   719  	}
   720  	sort.Strings(list)
   721  	return list
   722  }
   723  
   724  // sortedEmbeddeds returns constraint types embedded in an
   725  // interface. It does not include embedded interface types or methods.
   726  func (w *Walker) sortedEmbeddeds(typ *types.Interface) []string {
   727  	n := typ.NumEmbeddeds()
   728  	list := make([]string, 0, n)
   729  	for i := 0; i < n; i++ {
   730  		emb := typ.EmbeddedType(i)
   731  		switch emb := emb.(type) {
   732  		case *types.Interface:
   733  			list = append(list, w.sortedEmbeddeds(emb)...)
   734  		case *types.Union:
   735  			var buf bytes.Buffer
   736  			nu := emb.Len()
   737  			for i := 0; i < nu; i++ {
   738  				if i > 0 {
   739  					buf.WriteString(" | ")
   740  				}
   741  				term := emb.Term(i)
   742  				if term.Tilde() {
   743  					buf.WriteByte('~')
   744  				}
   745  				w.writeType(&buf, term.Type())
   746  			}
   747  			list = append(list, buf.String())
   748  		}
   749  	}
   750  	sort.Strings(list)
   751  	return list
   752  }
   753  
   754  func (w *Walker) writeType(buf *bytes.Buffer, typ types.Type) {
   755  	switch typ := typ.(type) {
   756  	case *types.Basic:
   757  		s := typ.Name()
   758  		switch typ.Kind() {
   759  		case types.UnsafePointer:
   760  			s = "unsafe.Pointer"
   761  		case types.UntypedBool:
   762  			s = "ideal-bool"
   763  		case types.UntypedInt:
   764  			s = "ideal-int"
   765  		case types.UntypedRune:
   766  			// "ideal-char" for compatibility with old tool
   767  			// TODO(gri) change to "ideal-rune"
   768  			s = "ideal-char"
   769  		case types.UntypedFloat:
   770  			s = "ideal-float"
   771  		case types.UntypedComplex:
   772  			s = "ideal-complex"
   773  		case types.UntypedString:
   774  			s = "ideal-string"
   775  		case types.UntypedNil:
   776  			panic("should never see untyped nil type")
   777  		default:
   778  			switch s {
   779  			case "byte":
   780  				s = "uint8"
   781  			case "rune":
   782  				s = "int32"
   783  			}
   784  		}
   785  		buf.WriteString(s)
   786  
   787  	case *types.Array:
   788  		fmt.Fprintf(buf, "[%d]", typ.Len())
   789  		w.writeType(buf, typ.Elem())
   790  
   791  	case *types.Slice:
   792  		buf.WriteString("[]")
   793  		w.writeType(buf, typ.Elem())
   794  
   795  	case *types.Struct:
   796  		buf.WriteString("struct")
   797  
   798  	case *types.Pointer:
   799  		buf.WriteByte('*')
   800  		w.writeType(buf, typ.Elem())
   801  
   802  	case *types.Tuple:
   803  		panic("should never see a tuple type")
   804  
   805  	case *types.Signature:
   806  		buf.WriteString("func")
   807  		w.writeSignature(buf, typ)
   808  
   809  	case *types.Interface:
   810  		buf.WriteString("interface{")
   811  		if typ.NumMethods() > 0 || typ.NumEmbeddeds() > 0 {
   812  			buf.WriteByte(' ')
   813  		}
   814  		if typ.NumMethods() > 0 {
   815  			buf.WriteString(strings.Join(sortedMethodNames(typ), ", "))
   816  		}
   817  		if typ.NumEmbeddeds() > 0 {
   818  			buf.WriteString(strings.Join(w.sortedEmbeddeds(typ), ", "))
   819  		}
   820  		if typ.NumMethods() > 0 || typ.NumEmbeddeds() > 0 {
   821  			buf.WriteByte(' ')
   822  		}
   823  		buf.WriteString("}")
   824  
   825  	case *types.Map:
   826  		buf.WriteString("map[")
   827  		w.writeType(buf, typ.Key())
   828  		buf.WriteByte(']')
   829  		w.writeType(buf, typ.Elem())
   830  
   831  	case *types.Chan:
   832  		var s string
   833  		switch typ.Dir() {
   834  		case types.SendOnly:
   835  			s = "chan<- "
   836  		case types.RecvOnly:
   837  			s = "<-chan "
   838  		case types.SendRecv:
   839  			s = "chan "
   840  		default:
   841  			panic("unreachable")
   842  		}
   843  		buf.WriteString(s)
   844  		w.writeType(buf, typ.Elem())
   845  
   846  	case *types.Alias:
   847  		w.writeType(buf, types.Unalias(typ))
   848  
   849  	case *types.Named:
   850  		obj := typ.Obj()
   851  		pkg := obj.Pkg()
   852  		if pkg != nil && pkg != w.current.Package {
   853  			buf.WriteString(pkg.Name())
   854  			buf.WriteByte('.')
   855  		}
   856  		buf.WriteString(typ.Obj().Name())
   857  		if targs := typ.TypeArgs(); targs.Len() > 0 {
   858  			buf.WriteByte('[')
   859  			for i := 0; i < targs.Len(); i++ {
   860  				if i > 0 {
   861  					buf.WriteString(", ")
   862  				}
   863  				w.writeType(buf, targs.At(i))
   864  			}
   865  			buf.WriteByte(']')
   866  		}
   867  
   868  	case *types.TypeParam:
   869  		// Type parameter names may change, so use a placeholder instead.
   870  		fmt.Fprintf(buf, "$%d", typ.Index())
   871  
   872  	default:
   873  		panic(fmt.Sprintf("unknown type %T", typ))
   874  	}
   875  }
   876  
   877  func (w *Walker) writeSignature(buf *bytes.Buffer, sig *types.Signature) {
   878  	if tparams := sig.TypeParams(); tparams != nil {
   879  		w.writeTypeParams(buf, tparams, true)
   880  	}
   881  	w.writeParams(buf, sig.Params(), sig.Variadic())
   882  	switch res := sig.Results(); res.Len() {
   883  	case 0:
   884  		// nothing to do
   885  	case 1:
   886  		buf.WriteByte(' ')
   887  		w.writeType(buf, res.At(0).Type())
   888  	default:
   889  		buf.WriteByte(' ')
   890  		w.writeParams(buf, res, false)
   891  	}
   892  }
   893  
   894  func (w *Walker) writeTypeParams(buf *bytes.Buffer, tparams *types.TypeParamList, withConstraints bool) {
   895  	buf.WriteByte('[')
   896  	c := tparams.Len()
   897  	for i := 0; i < c; i++ {
   898  		if i > 0 {
   899  			buf.WriteString(", ")
   900  		}
   901  		tp := tparams.At(i)
   902  		w.writeType(buf, tp)
   903  		if withConstraints {
   904  			buf.WriteByte(' ')
   905  			w.writeType(buf, tp.Constraint())
   906  		}
   907  	}
   908  	buf.WriteByte(']')
   909  }
   910  
   911  func (w *Walker) writeParams(buf *bytes.Buffer, t *types.Tuple, variadic bool) {
   912  	buf.WriteByte('(')
   913  	for i, n := 0, t.Len(); i < n; i++ {
   914  		if i > 0 {
   915  			buf.WriteString(", ")
   916  		}
   917  		typ := t.At(i).Type()
   918  		if variadic && i+1 == n {
   919  			buf.WriteString("...")
   920  			typ = typ.(*types.Slice).Elem()
   921  		}
   922  		w.writeType(buf, typ)
   923  	}
   924  	buf.WriteByte(')')
   925  }
   926  
   927  func (w *Walker) typeString(typ types.Type) string {
   928  	var buf bytes.Buffer
   929  	w.writeType(&buf, typ)
   930  	return buf.String()
   931  }
   932  
   933  func (w *Walker) signatureString(sig *types.Signature) string {
   934  	var buf bytes.Buffer
   935  	w.writeSignature(&buf, sig)
   936  	return buf.String()
   937  }
   938  
   939  func (w *Walker) emitObj(obj types.Object) {
   940  	switch obj := obj.(type) {
   941  	case *types.Const:
   942  		if w.isDeprecated(obj) {
   943  			w.emitf("const %s //deprecated", obj.Name())
   944  		}
   945  		w.emitf("const %s %s", obj.Name(), w.typeString(obj.Type()))
   946  		x := obj.Val()
   947  		short := x.String()
   948  		exact := x.ExactString()
   949  		if short == exact {
   950  			w.emitf("const %s = %s", obj.Name(), short)
   951  		} else {
   952  			w.emitf("const %s = %s  // %s", obj.Name(), short, exact)
   953  		}
   954  	case *types.Var:
   955  		if w.isDeprecated(obj) {
   956  			w.emitf("var %s //deprecated", obj.Name())
   957  		}
   958  		w.emitf("var %s %s", obj.Name(), w.typeString(obj.Type()))
   959  	case *types.TypeName:
   960  		w.emitType(obj)
   961  	case *types.Func:
   962  		w.emitFunc(obj)
   963  	default:
   964  		panic("unknown object: " + obj.String())
   965  	}
   966  }
   967  
   968  func (w *Walker) emitType(obj *types.TypeName) {
   969  	name := obj.Name()
   970  	if w.isDeprecated(obj) {
   971  		w.emitf("type %s //deprecated", name)
   972  	}
   973  	typ := obj.Type()
   974  	if obj.IsAlias() {
   975  		w.emitf("type %s = %s", name, w.typeString(typ))
   976  		return
   977  	}
   978  	if tparams := obj.Type().(*types.Named).TypeParams(); tparams != nil {
   979  		var buf bytes.Buffer
   980  		buf.WriteString(name)
   981  		w.writeTypeParams(&buf, tparams, true)
   982  		name = buf.String()
   983  	}
   984  	switch typ := typ.Underlying().(type) {
   985  	case *types.Struct:
   986  		w.emitStructType(name, typ)
   987  	case *types.Interface:
   988  		w.emitIfaceType(name, typ)
   989  		return // methods are handled by emitIfaceType
   990  	default:
   991  		w.emitf("type %s %s", name, w.typeString(typ.Underlying()))
   992  	}
   993  
   994  	// emit methods with value receiver
   995  	var methodNames map[string]bool
   996  	vset := types.NewMethodSet(typ)
   997  	for i, n := 0, vset.Len(); i < n; i++ {
   998  		m := vset.At(i)
   999  		if m.Obj().Exported() {
  1000  			w.emitMethod(m)
  1001  			if methodNames == nil {
  1002  				methodNames = make(map[string]bool)
  1003  			}
  1004  			methodNames[m.Obj().Name()] = true
  1005  		}
  1006  	}
  1007  
  1008  	// emit methods with pointer receiver; exclude
  1009  	// methods that we have emitted already
  1010  	// (the method set of *T includes the methods of T)
  1011  	pset := types.NewMethodSet(types.NewPointer(typ))
  1012  	for i, n := 0, pset.Len(); i < n; i++ {
  1013  		m := pset.At(i)
  1014  		if m.Obj().Exported() && !methodNames[m.Obj().Name()] {
  1015  			w.emitMethod(m)
  1016  		}
  1017  	}
  1018  }
  1019  
  1020  func (w *Walker) emitStructType(name string, typ *types.Struct) {
  1021  	typeStruct := fmt.Sprintf("type %s struct", name)
  1022  	w.emitf(typeStruct)
  1023  	defer w.pushScope(typeStruct)()
  1024  
  1025  	for i := 0; i < typ.NumFields(); i++ {
  1026  		f := typ.Field(i)
  1027  		if !f.Exported() {
  1028  			continue
  1029  		}
  1030  		typ := f.Type()
  1031  		if f.Anonymous() {
  1032  			if w.isDeprecated(f) {
  1033  				w.emitf("embedded %s //deprecated", w.typeString(typ))
  1034  			}
  1035  			w.emitf("embedded %s", w.typeString(typ))
  1036  			continue
  1037  		}
  1038  		if w.isDeprecated(f) {
  1039  			w.emitf("%s //deprecated", f.Name())
  1040  		}
  1041  		w.emitf("%s %s", f.Name(), w.typeString(typ))
  1042  	}
  1043  }
  1044  
  1045  func (w *Walker) emitIfaceType(name string, typ *types.Interface) {
  1046  	pop := w.pushScope("type " + name + " interface")
  1047  
  1048  	var methodNames []string
  1049  	complete := true
  1050  	mset := types.NewMethodSet(typ)
  1051  	for i, n := 0, mset.Len(); i < n; i++ {
  1052  		m := mset.At(i).Obj().(*types.Func)
  1053  		if !m.Exported() {
  1054  			complete = false
  1055  			continue
  1056  		}
  1057  		methodNames = append(methodNames, m.Name())
  1058  		if w.isDeprecated(m) {
  1059  			w.emitf("%s //deprecated", m.Name())
  1060  		}
  1061  		w.emitf("%s%s", m.Name(), w.signatureString(m.Type().(*types.Signature)))
  1062  	}
  1063  
  1064  	if !complete {
  1065  		// The method set has unexported methods, so all the
  1066  		// implementations are provided by the same package,
  1067  		// so the method set can be extended. Instead of recording
  1068  		// the full set of names (below), record only that there were
  1069  		// unexported methods. (If the interface shrinks, we will notice
  1070  		// because a method signature emitted during the last loop
  1071  		// will disappear.)
  1072  		w.emitf("unexported methods")
  1073  	}
  1074  
  1075  	pop()
  1076  
  1077  	if !complete {
  1078  		return
  1079  	}
  1080  
  1081  	if len(methodNames) == 0 {
  1082  		w.emitf("type %s interface {}", name)
  1083  		return
  1084  	}
  1085  
  1086  	sort.Strings(methodNames)
  1087  	w.emitf("type %s interface { %s }", name, strings.Join(methodNames, ", "))
  1088  }
  1089  
  1090  func (w *Walker) emitFunc(f *types.Func) {
  1091  	sig := f.Type().(*types.Signature)
  1092  	if sig.Recv() != nil {
  1093  		panic("method considered a regular function: " + f.String())
  1094  	}
  1095  	if w.isDeprecated(f) {
  1096  		w.emitf("func %s //deprecated", f.Name())
  1097  	}
  1098  	w.emitf("func %s%s", f.Name(), w.signatureString(sig))
  1099  }
  1100  
  1101  func (w *Walker) emitMethod(m *types.Selection) {
  1102  	sig := m.Type().(*types.Signature)
  1103  	recv := sig.Recv().Type()
  1104  	// report exported methods with unexported receiver base type
  1105  	if true {
  1106  		base := recv
  1107  		if p, _ := recv.(*types.Pointer); p != nil {
  1108  			base = p.Elem()
  1109  		}
  1110  		if obj := base.(*types.Named).Obj(); !obj.Exported() {
  1111  			log.Fatalf("exported method with unexported receiver base type: %s", m)
  1112  		}
  1113  	}
  1114  	tps := ""
  1115  	if rtp := sig.RecvTypeParams(); rtp != nil {
  1116  		var buf bytes.Buffer
  1117  		w.writeTypeParams(&buf, rtp, false)
  1118  		tps = buf.String()
  1119  	}
  1120  	if w.isDeprecated(m.Obj()) {
  1121  		w.emitf("method (%s%s) %s //deprecated", w.typeString(recv), tps, m.Obj().Name())
  1122  	}
  1123  	w.emitf("method (%s%s) %s%s", w.typeString(recv), tps, m.Obj().Name(), w.signatureString(sig))
  1124  }
  1125  
  1126  func (w *Walker) emitf(format string, args ...any) {
  1127  	f := strings.Join(w.scope, ", ") + ", " + fmt.Sprintf(format, args...)
  1128  	if strings.Contains(f, "\n") {
  1129  		panic("feature contains newlines: " + f)
  1130  	}
  1131  
  1132  	if _, dup := w.features[f]; dup {
  1133  		panic("duplicate feature inserted: " + f)
  1134  	}
  1135  	w.features[f] = true
  1136  
  1137  	if verbose {
  1138  		log.Printf("feature: %s", f)
  1139  	}
  1140  }
  1141  
  1142  func needApproval(filename string) bool {
  1143  	name := filepath.Base(filename)
  1144  	if name == "go1.txt" {
  1145  		return false
  1146  	}
  1147  	minor := strings.TrimSuffix(strings.TrimPrefix(name, "go1."), ".txt")
  1148  	n, err := strconv.Atoi(minor)
  1149  	if err != nil {
  1150  		log.Fatalf("unexpected api file: %v", name)
  1151  	}
  1152  	return n >= 19 // started tracking approvals in Go 1.19
  1153  }
  1154  
  1155  func (w *Walker) collectDeprecated() {
  1156  	isDeprecated := func(doc *ast.CommentGroup) bool {
  1157  		if doc != nil {
  1158  			for _, c := range doc.List {
  1159  				if strings.HasPrefix(c.Text, "// Deprecated:") {
  1160  					return true
  1161  				}
  1162  			}
  1163  		}
  1164  		return false
  1165  	}
  1166  
  1167  	w.deprecated = make(map[token.Pos]bool)
  1168  	mark := func(id *ast.Ident) {
  1169  		if id != nil {
  1170  			w.deprecated[id.Pos()] = true
  1171  		}
  1172  	}
  1173  	for _, file := range w.current.Files {
  1174  		ast.Inspect(file, func(n ast.Node) bool {
  1175  			switch n := n.(type) {
  1176  			case *ast.File:
  1177  				if isDeprecated(n.Doc) {
  1178  					mark(n.Name)
  1179  				}
  1180  				return true
  1181  			case *ast.GenDecl:
  1182  				if isDeprecated(n.Doc) {
  1183  					for _, spec := range n.Specs {
  1184  						switch spec := spec.(type) {
  1185  						case *ast.ValueSpec:
  1186  							for _, id := range spec.Names {
  1187  								mark(id)
  1188  							}
  1189  						case *ast.TypeSpec:
  1190  							mark(spec.Name)
  1191  						}
  1192  					}
  1193  				}
  1194  				return true // look at specs
  1195  			case *ast.FuncDecl:
  1196  				if isDeprecated(n.Doc) {
  1197  					mark(n.Name)
  1198  				}
  1199  				return false
  1200  			case *ast.TypeSpec:
  1201  				if isDeprecated(n.Doc) {
  1202  					mark(n.Name)
  1203  				}
  1204  				return true // recurse into struct or interface type
  1205  			case *ast.StructType:
  1206  				return true // recurse into fields
  1207  			case *ast.InterfaceType:
  1208  				return true // recurse into methods
  1209  			case *ast.FieldList:
  1210  				return true // recurse into fields
  1211  			case *ast.ValueSpec:
  1212  				if isDeprecated(n.Doc) {
  1213  					for _, id := range n.Names {
  1214  						mark(id)
  1215  					}
  1216  				}
  1217  				return false
  1218  			case *ast.Field:
  1219  				if isDeprecated(n.Doc) {
  1220  					for _, id := range n.Names {
  1221  						mark(id)
  1222  					}
  1223  					if len(n.Names) == 0 {
  1224  						// embedded field T or *T?
  1225  						typ := n.Type
  1226  						if ptr, ok := typ.(*ast.StarExpr); ok {
  1227  							typ = ptr.X
  1228  						}
  1229  						if id, ok := typ.(*ast.Ident); ok {
  1230  							mark(id)
  1231  						}
  1232  					}
  1233  				}
  1234  				return false
  1235  			default:
  1236  				return false
  1237  			}
  1238  		})
  1239  	}
  1240  }
  1241  
  1242  func (w *Walker) isDeprecated(obj types.Object) bool {
  1243  	return w.deprecated[obj.Pos()]
  1244  }
  1245  

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