1 // Copyright 2018 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 package modfetch 6 7 import ( 8 "context" 9 "fmt" 10 "io" 11 "io/fs" 12 "os" 13 "strconv" 14 "time" 15 16 "cmd/go/internal/cfg" 17 "cmd/go/internal/modfetch/codehost" 18 "cmd/go/internal/par" 19 "cmd/go/internal/vcs" 20 web "cmd/go/internal/web" 21 22 "golang.org/x/mod/module" 23 ) 24 25 const traceRepo = false // trace all repo actions, for debugging 26 27 // A Repo represents a repository storing all versions of a single module. 28 // It must be safe for simultaneous use by multiple goroutines. 29 type Repo interface { 30 // ModulePath returns the module path. 31 ModulePath() string 32 33 // CheckReuse checks whether the validation criteria in the origin 34 // are still satisfied on the server corresponding to this module. 35 // If so, the caller can reuse any cached Versions or RevInfo containing 36 // this origin rather than redownloading those from the server. 37 CheckReuse(ctx context.Context, old *codehost.Origin) error 38 39 // Versions lists all known versions with the given prefix. 40 // Pseudo-versions are not included. 41 // 42 // Versions should be returned sorted in semver order 43 // (implementations can use semver.Sort). 44 // 45 // Versions returns a non-nil error only if there was a problem 46 // fetching the list of versions: it may return an empty list 47 // along with a nil error if the list of matching versions 48 // is known to be empty. 49 // 50 // If the underlying repository does not exist, 51 // Versions returns an error matching errors.Is(_, os.NotExist). 52 Versions(ctx context.Context, prefix string) (*Versions, error) 53 54 // Stat returns information about the revision rev. 55 // A revision can be any identifier known to the underlying service: 56 // commit hash, branch, tag, and so on. 57 Stat(ctx context.Context, rev string) (*RevInfo, error) 58 59 // Latest returns the latest revision on the default branch, 60 // whatever that means in the underlying source code repository. 61 // It is only used when there are no tagged versions. 62 Latest(ctx context.Context) (*RevInfo, error) 63 64 // GoMod returns the go.mod file for the given version. 65 GoMod(ctx context.Context, version string) (data []byte, err error) 66 67 // Zip writes a zip file for the given version to dst. 68 Zip(ctx context.Context, dst io.Writer, version string) error 69 } 70 71 // A Versions describes the available versions in a module repository. 72 type Versions struct { 73 Origin *codehost.Origin `json:",omitempty"` // origin information for reuse 74 75 List []string // semver versions 76 } 77 78 // A RevInfo describes a single revision in a module repository. 79 type RevInfo struct { 80 Version string // suggested version string for this revision 81 Time time.Time // commit time 82 83 // These fields are used for Stat of arbitrary rev, 84 // but they are not recorded when talking about module versions. 85 Name string `json:"-"` // complete ID in underlying repository 86 Short string `json:"-"` // shortened ID, for use in pseudo-version 87 88 Origin *codehost.Origin `json:",omitempty"` // provenance for reuse 89 } 90 91 // Re: module paths, import paths, repository roots, and lookups 92 // 93 // A module is a collection of Go packages stored in a file tree 94 // with a go.mod file at the root of the tree. 95 // The go.mod defines the module path, which is the import path 96 // corresponding to the root of the file tree. 97 // The import path of a directory within that file tree is the module path 98 // joined with the name of the subdirectory relative to the root. 99 // 100 // For example, the module with path rsc.io/qr corresponds to the 101 // file tree in the repository https://github.com/rsc/qr. 102 // That file tree has a go.mod that says "module rsc.io/qr". 103 // The package in the root directory has import path "rsc.io/qr". 104 // The package in the gf256 subdirectory has import path "rsc.io/qr/gf256". 105 // In this example, "rsc.io/qr" is both a module path and an import path. 106 // But "rsc.io/qr/gf256" is only an import path, not a module path: 107 // it names an importable package, but not a module. 108 // 109 // As a special case to incorporate code written before modules were 110 // introduced, if a path p resolves using the pre-module "go get" lookup 111 // to the root of a source code repository without a go.mod file, 112 // that repository is treated as if it had a go.mod in its root directory 113 // declaring module path p. (The go.mod is further considered to 114 // contain requirements corresponding to any legacy version 115 // tracking format such as Gopkg.lock, vendor/vendor.conf, and so on.) 116 // 117 // The presentation so far ignores the fact that a source code repository 118 // has many different versions of a file tree, and those versions may 119 // differ in whether a particular go.mod exists and what it contains. 120 // In fact there is a well-defined mapping only from a module path, version 121 // pair - often written path@version - to a particular file tree. 122 // For example rsc.io/qr@v0.1.0 depends on the "implicit go.mod at root of 123 // repository" rule, while rsc.io/qr@v0.2.0 has an explicit go.mod. 124 // Because the "go get" import paths rsc.io/qr and github.com/rsc/qr 125 // both redirect to the Git repository https://github.com/rsc/qr, 126 // github.com/rsc/qr@v0.1.0 is the same file tree as rsc.io/qr@v0.1.0 127 // but a different module (a different name). In contrast, since v0.2.0 128 // of that repository has an explicit go.mod that declares path rsc.io/qr, 129 // github.com/rsc/qr@v0.2.0 is an invalid module path, version pair. 130 // Before modules, import comments would have had the same effect. 131 // 132 // The set of import paths associated with a given module path is 133 // clearly not fixed: at the least, new directories with new import paths 134 // can always be added. But another potential operation is to split a 135 // subtree out of a module into its own module. If done carefully, 136 // this operation can be done while preserving compatibility for clients. 137 // For example, suppose that we want to split rsc.io/qr/gf256 into its 138 // own module, so that there would be two modules rsc.io/qr and rsc.io/qr/gf256. 139 // Then we can simultaneously issue rsc.io/qr v0.3.0 (dropping the gf256 subdirectory) 140 // and rsc.io/qr/gf256 v0.1.0, including in their respective go.mod 141 // cyclic requirements pointing at each other: rsc.io/qr v0.3.0 requires 142 // rsc.io/qr/gf256 v0.1.0 and vice versa. Then a build can be 143 // using an older rsc.io/qr module that includes the gf256 package, but if 144 // it adds a requirement on either the newer rsc.io/qr or the newer 145 // rsc.io/qr/gf256 module, it will automatically add the requirement 146 // on the complementary half, ensuring both that rsc.io/qr/gf256 is 147 // available for importing by the build and also that it is only defined 148 // by a single module. The gf256 package could move back into the 149 // original by another simultaneous release of rsc.io/qr v0.4.0 including 150 // the gf256 subdirectory and an rsc.io/qr/gf256 v0.2.0 with no code 151 // in its root directory, along with a new requirement cycle. 152 // The ability to shift module boundaries in this way is expected to be 153 // important in large-scale program refactorings, similar to the ones 154 // described in https://talks.golang.org/2016/refactor.article. 155 // 156 // The possibility of shifting module boundaries reemphasizes 157 // that you must know both the module path and its version 158 // to determine the set of packages provided directly by that module. 159 // 160 // On top of all this, it is possible for a single code repository 161 // to contain multiple modules, either in branches or subdirectories, 162 // as a limited kind of monorepo. For example rsc.io/qr/v2, 163 // the v2.x.x continuation of rsc.io/qr, is expected to be found 164 // in v2-tagged commits in https://github.com/rsc/qr, either 165 // in the root or in a v2 subdirectory, disambiguated by go.mod. 166 // Again the precise file tree corresponding to a module 167 // depends on which version we are considering. 168 // 169 // It is also possible for the underlying repository to change over time, 170 // without changing the module path. If I copy the github repo over 171 // to https://bitbucket.org/rsc/qr and update https://rsc.io/qr?go-get=1, 172 // then clients of all versions should start fetching from bitbucket 173 // instead of github. That is, in contrast to the exact file tree, 174 // the location of the source code repository associated with a module path 175 // does not depend on the module version. (This is by design, as the whole 176 // point of these redirects is to allow package authors to establish a stable 177 // name that can be updated as code moves from one service to another.) 178 // 179 // All of this is important background for the lookup APIs defined in this 180 // file. 181 // 182 // The Lookup function takes a module path and returns a Repo representing 183 // that module path. Lookup can do only a little with the path alone. 184 // It can check that the path is well-formed (see semver.CheckPath) 185 // and it can check that the path can be resolved to a target repository. 186 // To avoid version control access except when absolutely necessary, 187 // Lookup does not attempt to connect to the repository itself. 188 189 var lookupCache par.Cache[lookupCacheKey, Repo] 190 191 type lookupCacheKey struct { 192 proxy, path string 193 } 194 195 // Lookup returns the module with the given module path, 196 // fetched through the given proxy. 197 // 198 // The distinguished proxy "direct" indicates that the path should be fetched 199 // from its origin, and "noproxy" indicates that the patch should be fetched 200 // directly only if GONOPROXY matches the given path. 201 // 202 // For the distinguished proxy "off", Lookup always returns a Repo that returns 203 // a non-nil error for every method call. 204 // 205 // A successful return does not guarantee that the module 206 // has any defined versions. 207 func Lookup(ctx context.Context, proxy, path string) Repo { 208 if traceRepo { 209 defer logCall("Lookup(%q, %q)", proxy, path)() 210 } 211 212 return lookupCache.Do(lookupCacheKey{proxy, path}, func() Repo { 213 return newCachingRepo(ctx, path, func(ctx context.Context) (Repo, error) { 214 r, err := lookup(ctx, proxy, path) 215 if err == nil && traceRepo { 216 r = newLoggingRepo(r) 217 } 218 return r, err 219 }) 220 }) 221 } 222 223 // lookup returns the module with the given module path. 224 func lookup(ctx context.Context, proxy, path string) (r Repo, err error) { 225 if cfg.BuildMod == "vendor" { 226 return nil, errLookupDisabled 227 } 228 229 switch path { 230 case "go", "toolchain": 231 return &toolchainRepo{path, Lookup(ctx, proxy, "golang.org/toolchain")}, nil 232 } 233 234 if module.MatchPrefixPatterns(cfg.GONOPROXY, path) { 235 switch proxy { 236 case "noproxy", "direct": 237 return lookupDirect(ctx, path) 238 default: 239 return nil, errNoproxy 240 } 241 } 242 243 switch proxy { 244 case "off": 245 return errRepo{path, errProxyOff}, nil 246 case "direct": 247 return lookupDirect(ctx, path) 248 case "noproxy": 249 return nil, errUseProxy 250 default: 251 return newProxyRepo(proxy, path) 252 } 253 } 254 255 type lookupDisabledError struct{} 256 257 func (lookupDisabledError) Error() string { 258 if cfg.BuildModReason == "" { 259 return fmt.Sprintf("module lookup disabled by -mod=%s", cfg.BuildMod) 260 } 261 return fmt.Sprintf("module lookup disabled by -mod=%s\n\t(%s)", cfg.BuildMod, cfg.BuildModReason) 262 } 263 264 var errLookupDisabled error = lookupDisabledError{} 265 266 var ( 267 errProxyOff = notExistErrorf("module lookup disabled by GOPROXY=off") 268 errNoproxy error = notExistErrorf("disabled by GOPRIVATE/GONOPROXY") 269 errUseProxy error = notExistErrorf("path does not match GOPRIVATE/GONOPROXY") 270 ) 271 272 func lookupDirect(ctx context.Context, path string) (Repo, error) { 273 security := web.SecureOnly 274 275 if module.MatchPrefixPatterns(cfg.GOINSECURE, path) { 276 security = web.Insecure 277 } 278 rr, err := vcs.RepoRootForImportPath(path, vcs.PreferMod, security) 279 if err != nil { 280 // We don't know where to find code for a module with this path. 281 return nil, notExistError{err: err} 282 } 283 284 if rr.VCS.Name == "mod" { 285 // Fetch module from proxy with base URL rr.Repo. 286 return newProxyRepo(rr.Repo, path) 287 } 288 289 code, err := lookupCodeRepo(ctx, rr) 290 if err != nil { 291 return nil, err 292 } 293 return newCodeRepo(code, rr.Root, path) 294 } 295 296 func lookupCodeRepo(ctx context.Context, rr *vcs.RepoRoot) (codehost.Repo, error) { 297 code, err := codehost.NewRepo(ctx, rr.VCS.Cmd, rr.Repo) 298 if err != nil { 299 if _, ok := err.(*codehost.VCSError); ok { 300 return nil, err 301 } 302 return nil, fmt.Errorf("lookup %s: %v", rr.Root, err) 303 } 304 return code, nil 305 } 306 307 // A loggingRepo is a wrapper around an underlying Repo 308 // that prints a log message at the start and end of each call. 309 // It can be inserted when debugging. 310 type loggingRepo struct { 311 r Repo 312 } 313 314 func newLoggingRepo(r Repo) *loggingRepo { 315 return &loggingRepo{r} 316 } 317 318 // logCall prints a log message using format and args and then 319 // also returns a function that will print the same message again, 320 // along with the elapsed time. 321 // Typical usage is: 322 // 323 // defer logCall("hello %s", arg)() 324 // 325 // Note the final (). 326 func logCall(format string, args ...any) func() { 327 start := time.Now() 328 fmt.Fprintf(os.Stderr, "+++ %s\n", fmt.Sprintf(format, args...)) 329 return func() { 330 fmt.Fprintf(os.Stderr, "%.3fs %s\n", time.Since(start).Seconds(), fmt.Sprintf(format, args...)) 331 } 332 } 333 334 func (l *loggingRepo) ModulePath() string { 335 return l.r.ModulePath() 336 } 337 338 func (l *loggingRepo) CheckReuse(ctx context.Context, old *codehost.Origin) (err error) { 339 defer func() { 340 logCall("CheckReuse[%s]: %v", l.r.ModulePath(), err) 341 }() 342 return l.r.CheckReuse(ctx, old) 343 } 344 345 func (l *loggingRepo) Versions(ctx context.Context, prefix string) (*Versions, error) { 346 defer logCall("Repo[%s]: Versions(%q)", l.r.ModulePath(), prefix)() 347 return l.r.Versions(ctx, prefix) 348 } 349 350 func (l *loggingRepo) Stat(ctx context.Context, rev string) (*RevInfo, error) { 351 defer logCall("Repo[%s]: Stat(%q)", l.r.ModulePath(), rev)() 352 return l.r.Stat(ctx, rev) 353 } 354 355 func (l *loggingRepo) Latest(ctx context.Context) (*RevInfo, error) { 356 defer logCall("Repo[%s]: Latest()", l.r.ModulePath())() 357 return l.r.Latest(ctx) 358 } 359 360 func (l *loggingRepo) GoMod(ctx context.Context, version string) ([]byte, error) { 361 defer logCall("Repo[%s]: GoMod(%q)", l.r.ModulePath(), version)() 362 return l.r.GoMod(ctx, version) 363 } 364 365 func (l *loggingRepo) Zip(ctx context.Context, dst io.Writer, version string) error { 366 dstName := "_" 367 if dst, ok := dst.(interface{ Name() string }); ok { 368 dstName = strconv.Quote(dst.Name()) 369 } 370 defer logCall("Repo[%s]: Zip(%s, %q)", l.r.ModulePath(), dstName, version)() 371 return l.r.Zip(ctx, dst, version) 372 } 373 374 // errRepo is a Repo that returns the same error for all operations. 375 // 376 // It is useful in conjunction with caching, since cache hits will not attempt 377 // the prohibited operations. 378 type errRepo struct { 379 modulePath string 380 err error 381 } 382 383 func (r errRepo) ModulePath() string { return r.modulePath } 384 385 func (r errRepo) CheckReuse(ctx context.Context, old *codehost.Origin) error { return r.err } 386 func (r errRepo) Versions(ctx context.Context, prefix string) (*Versions, error) { return nil, r.err } 387 func (r errRepo) Stat(ctx context.Context, rev string) (*RevInfo, error) { return nil, r.err } 388 func (r errRepo) Latest(ctx context.Context) (*RevInfo, error) { return nil, r.err } 389 func (r errRepo) GoMod(ctx context.Context, version string) ([]byte, error) { return nil, r.err } 390 func (r errRepo) Zip(ctx context.Context, dst io.Writer, version string) error { return r.err } 391 392 // A notExistError is like fs.ErrNotExist, but with a custom message 393 type notExistError struct { 394 err error 395 } 396 397 func notExistErrorf(format string, args ...any) error { 398 return notExistError{fmt.Errorf(format, args...)} 399 } 400 401 func (e notExistError) Error() string { 402 return e.err.Error() 403 } 404 405 func (notExistError) Is(target error) bool { 406 return target == fs.ErrNotExist 407 } 408 409 func (e notExistError) Unwrap() error { 410 return e.err 411 } 412