func.go

Documentation: cmd/cover

     1  // Copyright 2013 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 file implements the visitor that computes the (line, column)-(line-column) range for each function.
     6  
     7  package main
     8  
     9  import (
    10  	"bufio"
    11  	"bytes"
    12  	"encoding/json"
    13  	"errors"
    14  	"fmt"
    15  	"go/ast"
    16  	"go/parser"
    17  	"go/token"
    18  	"io"
    19  	"os"
    20  	"os/exec"
    21  	"path"
    22  	"path/filepath"
    23  	"runtime"
    24  	"strings"
    25  	"text/tabwriter"
    26  
    27  	"golang.org/x/tools/cover"
    28  )
    29  
    30  // funcOutput takes two file names as arguments, a coverage profile to read as input and an output
    31  // file to write ("" means to write to standard output). The function reads the profile and produces
    32  // as output the coverage data broken down by function, like this:
    33  //
    34  //	fmt/format.go:30:	init			100.0%
    35  //	fmt/format.go:57:	clearflags		100.0%
    36  //	...
    37  //	fmt/scan.go:1046:	doScan			100.0%
    38  //	fmt/scan.go:1075:	advance			96.2%
    39  //	fmt/scan.go:1119:	doScanf			96.8%
    40  //	total:		(statements)			91.9%
    41  
    42  func funcOutput(profile, outputFile string) error {
    43  	profiles, err := cover.ParseProfiles(profile)
    44  	if err != nil {
    45  		return err
    46  	}
    47  
    48  	dirs, err := findPkgs(profiles)
    49  	if err != nil {
    50  		return err
    51  	}
    52  
    53  	var out *bufio.Writer
    54  	if outputFile == "" {
    55  		out = bufio.NewWriter(os.Stdout)
    56  	} else {
    57  		fd, err := os.Create(outputFile)
    58  		if err != nil {
    59  			return err
    60  		}
    61  		defer fd.Close()
    62  		out = bufio.NewWriter(fd)
    63  	}
    64  	defer out.Flush()
    65  
    66  	tabber := tabwriter.NewWriter(out, 1, 8, 1, '\t', 0)
    67  	defer tabber.Flush()
    68  
    69  	var total, covered int64
    70  	for _, profile := range profiles {
    71  		fn := profile.FileName
    72  		file, err := findFile(dirs, fn)
    73  		if err != nil {
    74  			return err
    75  		}
    76  		funcs, err := findFuncs(file)
    77  		if err != nil {
    78  			return err
    79  		}
    80  		// Now match up functions and profile blocks.
    81  		for _, f := range funcs {
    82  			c, t := f.coverage(profile)
    83  			fmt.Fprintf(tabber, "%s:%d:\t%s\t%.1f%%\n", fn, f.startLine, f.name, percent(c, t))
    84  			total += t
    85  			covered += c
    86  		}
    87  	}
    88  	fmt.Fprintf(tabber, "total:\t(statements)\t%.1f%%\n", percent(covered, total))
    89  
    90  	return nil
    91  }
    92  
    93  // findFuncs parses the file and returns a slice of FuncExtent descriptors.
    94  func findFuncs(name string) ([]*FuncExtent, error) {
    95  	fset := token.NewFileSet()
    96  	parsedFile, err := parser.ParseFile(fset, name, nil, 0)
    97  	if err != nil {
    98  		return nil, err
    99  	}
   100  	visitor := &FuncVisitor{
   101  		fset:    fset,
   102  		name:    name,
   103  		astFile: parsedFile,
   104  	}
   105  	ast.Walk(visitor, visitor.astFile)
   106  	return visitor.funcs, nil
   107  }
   108  
   109  // FuncExtent describes a function's extent in the source by file and position.
   110  type FuncExtent struct {
   111  	name      string
   112  	startLine int
   113  	startCol  int
   114  	endLine   int
   115  	endCol    int
   116  }
   117  
   118  // FuncVisitor implements the visitor that builds the function position list for a file.
   119  type FuncVisitor struct {
   120  	fset    *token.FileSet
   121  	name    string // Name of file.
   122  	astFile *ast.File
   123  	funcs   []*FuncExtent
   124  }
   125  
   126  // Visit implements the ast.Visitor interface.
   127  func (v *FuncVisitor) Visit(node ast.Node) ast.Visitor {
   128  	switch n := node.(type) {
   129  	case *ast.FuncDecl:
   130  		if n.Body == nil {
   131  			// Do not count declarations of assembly functions.
   132  			break
   133  		}
   134  		start := v.fset.Position(n.Pos())
   135  		end := v.fset.Position(n.End())
   136  		fe := &FuncExtent{
   137  			name:      n.Name.Name,
   138  			startLine: start.Line,
   139  			startCol:  start.Column,
   140  			endLine:   end.Line,
   141  			endCol:    end.Column,
   142  		}
   143  		v.funcs = append(v.funcs, fe)
   144  	}
   145  	return v
   146  }
   147  
   148  // coverage returns the fraction of the statements in the function that were covered, as a numerator and denominator.
   149  func (f *FuncExtent) coverage(profile *cover.Profile) (num, den int64) {
   150  	// We could avoid making this n^2 overall by doing a single scan and annotating the functions,
   151  	// but the sizes of the data structures is never very large and the scan is almost instantaneous.
   152  	var covered, total int64
   153  	// The blocks are sorted, so we can stop counting as soon as we reach the end of the relevant block.
   154  	for _, b := range profile.Blocks {
   155  		if b.StartLine > f.endLine || (b.StartLine == f.endLine && b.StartCol >= f.endCol) {
   156  			// Past the end of the function.
   157  			break
   158  		}
   159  		if b.EndLine < f.startLine || (b.EndLine == f.startLine && b.EndCol <= f.startCol) {
   160  			// Before the beginning of the function
   161  			continue
   162  		}
   163  		total += int64(b.NumStmt)
   164  		if b.Count > 0 {
   165  			covered += int64(b.NumStmt)
   166  		}
   167  	}
   168  	return covered, total
   169  }
   170  
   171  // Pkg describes a single package, compatible with the JSON output from 'go list'; see 'go help list'.
   172  type Pkg struct {
   173  	ImportPath string
   174  	Dir        string
   175  	Error      *struct {
   176  		Err string
   177  	}
   178  }
   179  
   180  func findPkgs(profiles []*cover.Profile) (map[string]*Pkg, error) {
   181  	// Run go list to find the location of every package we care about.
   182  	pkgs := make(map[string]*Pkg)
   183  	var list []string
   184  	for _, profile := range profiles {
   185  		if strings.HasPrefix(profile.FileName, ".") || filepath.IsAbs(profile.FileName) {
   186  			// Relative or absolute path.
   187  			continue
   188  		}
   189  		pkg := path.Dir(profile.FileName)
   190  		if _, ok := pkgs[pkg]; !ok {
   191  			pkgs[pkg] = nil
   192  			list = append(list, pkg)
   193  		}
   194  	}
   195  
   196  	if len(list) == 0 {
   197  		return pkgs, nil
   198  	}
   199  
   200  	// Note: usually run as "go tool cover" in which case $GOROOT is set,
   201  	// in which case runtime.GOROOT() does exactly what we want.
   202  	goTool := filepath.Join(runtime.GOROOT(), "bin/go")
   203  	cmd := exec.Command(goTool, append([]string{"list", "-e", "-json"}, list...)...)
   204  	var stderr bytes.Buffer
   205  	cmd.Stderr = &stderr
   206  	stdout, err := cmd.Output()
   207  	if err != nil {
   208  		return nil, fmt.Errorf("cannot run go list: %v\n%s", err, stderr.Bytes())
   209  	}
   210  	dec := json.NewDecoder(bytes.NewReader(stdout))
   211  	for {
   212  		var pkg Pkg
   213  		err := dec.Decode(&pkg)
   214  		if err == io.EOF {
   215  			break
   216  		}
   217  		if err != nil {
   218  			return nil, fmt.Errorf("decoding go list json: %v", err)
   219  		}
   220  		pkgs[pkg.ImportPath] = &pkg
   221  	}
   222  	return pkgs, nil
   223  }
   224  
   225  // findFile finds the location of the named file in GOROOT, GOPATH etc.
   226  func findFile(pkgs map[string]*Pkg, file string) (string, error) {
   227  	if strings.HasPrefix(file, ".") || filepath.IsAbs(file) {
   228  		// Relative or absolute path.
   229  		return file, nil
   230  	}
   231  	pkg := pkgs[path.Dir(file)]
   232  	if pkg != nil {
   233  		if pkg.Dir != "" {
   234  			return filepath.Join(pkg.Dir, path.Base(file)), nil
   235  		}
   236  		if pkg.Error != nil {
   237  			return "", errors.New(pkg.Error.Err)
   238  		}
   239  	}
   240  	return "", fmt.Errorf("did not find package for %s in go list output", file)
   241  }
   242  
   243  func percent(covered, total int64) float64 {
   244  	if total == 0 {
   245  		total = 1 // Avoid zero denominator.
   246  	}
   247  	return 100.0 * float64(covered) / float64(total)
   248  }
   249
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