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Source file src/cmd/cover/func.go

Documentation: cmd/cover

  // Copyright 2013 The Go Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style
  // license that can be found in the LICENSE file.
  
  // This file implements the visitor that computes the (line, column)-(line-column) range for each function.
  
  package main
  
  import (
  	"bufio"
  	"fmt"
  	"go/ast"
  	"go/build"
  	"go/parser"
  	"go/token"
  	"os"
  	"path/filepath"
  	"text/tabwriter"
  )
  
  // funcOutput takes two file names as arguments, a coverage profile to read as input and an output
  // file to write ("" means to write to standard output). The function reads the profile and produces
  // as output the coverage data broken down by function, like this:
  //
  //	fmt/format.go:30:	init			100.0%
  //	fmt/format.go:57:	clearflags		100.0%
  //	...
  //	fmt/scan.go:1046:	doScan			100.0%
  //	fmt/scan.go:1075:	advance			96.2%
  //	fmt/scan.go:1119:	doScanf			96.8%
  //	total:		(statements)			91.9%
  
  func funcOutput(profile, outputFile string) error {
  	profiles, err := ParseProfiles(profile)
  	if err != nil {
  		return err
  	}
  
  	var out *bufio.Writer
  	if outputFile == "" {
  		out = bufio.NewWriter(os.Stdout)
  	} else {
  		fd, err := os.Create(outputFile)
  		if err != nil {
  			return err
  		}
  		defer fd.Close()
  		out = bufio.NewWriter(fd)
  	}
  	defer out.Flush()
  
  	tabber := tabwriter.NewWriter(out, 1, 8, 1, '\t', 0)
  	defer tabber.Flush()
  
  	var total, covered int64
  	for _, profile := range profiles {
  		fn := profile.FileName
  		file, err := findFile(fn)
  		if err != nil {
  			return err
  		}
  		funcs, err := findFuncs(file)
  		if err != nil {
  			return err
  		}
  		// Now match up functions and profile blocks.
  		for _, f := range funcs {
  			c, t := f.coverage(profile)
  			fmt.Fprintf(tabber, "%s:%d:\t%s\t%.1f%%\n", fn, f.startLine, f.name, percent(c, t))
  			total += t
  			covered += c
  		}
  	}
  	fmt.Fprintf(tabber, "total:\t(statements)\t%.1f%%\n", percent(covered, total))
  
  	return nil
  }
  
  // findFuncs parses the file and returns a slice of FuncExtent descriptors.
  func findFuncs(name string) ([]*FuncExtent, error) {
  	fset := token.NewFileSet()
  	parsedFile, err := parser.ParseFile(fset, name, nil, 0)
  	if err != nil {
  		return nil, err
  	}
  	visitor := &FuncVisitor{
  		fset:    fset,
  		name:    name,
  		astFile: parsedFile,
  	}
  	ast.Walk(visitor, visitor.astFile)
  	return visitor.funcs, nil
  }
  
  // FuncExtent describes a function's extent in the source by file and position.
  type FuncExtent struct {
  	name      string
  	startLine int
  	startCol  int
  	endLine   int
  	endCol    int
  }
  
  // FuncVisitor implements the visitor that builds the function position list for a file.
  type FuncVisitor struct {
  	fset    *token.FileSet
  	name    string // Name of file.
  	astFile *ast.File
  	funcs   []*FuncExtent
  }
  
  // Visit implements the ast.Visitor interface.
  func (v *FuncVisitor) Visit(node ast.Node) ast.Visitor {
  	switch n := node.(type) {
  	case *ast.FuncDecl:
  		start := v.fset.Position(n.Pos())
  		end := v.fset.Position(n.End())
  		fe := &FuncExtent{
  			name:      n.Name.Name,
  			startLine: start.Line,
  			startCol:  start.Column,
  			endLine:   end.Line,
  			endCol:    end.Column,
  		}
  		v.funcs = append(v.funcs, fe)
  	}
  	return v
  }
  
  // coverage returns the fraction of the statements in the function that were covered, as a numerator and denominator.
  func (f *FuncExtent) coverage(profile *Profile) (num, den int64) {
  	// We could avoid making this n^2 overall by doing a single scan and annotating the functions,
  	// but the sizes of the data structures is never very large and the scan is almost instantaneous.
  	var covered, total int64
  	// The blocks are sorted, so we can stop counting as soon as we reach the end of the relevant block.
  	for _, b := range profile.Blocks {
  		if b.StartLine > f.endLine || (b.StartLine == f.endLine && b.StartCol >= f.endCol) {
  			// Past the end of the function.
  			break
  		}
  		if b.EndLine < f.startLine || (b.EndLine == f.startLine && b.EndCol <= f.startCol) {
  			// Before the beginning of the function
  			continue
  		}
  		total += int64(b.NumStmt)
  		if b.Count > 0 {
  			covered += int64(b.NumStmt)
  		}
  	}
  	return covered, total
  }
  
  // findFile finds the location of the named file in GOROOT, GOPATH etc.
  func findFile(file string) (string, error) {
  	dir, file := filepath.Split(file)
  	pkg, err := build.Import(dir, ".", build.FindOnly)
  	if err != nil {
  		return "", fmt.Errorf("can't find %q: %v", file, err)
  	}
  	return filepath.Join(pkg.Dir, file), nil
  }
  
  func percent(covered, total int64) float64 {
  	if total == 0 {
  		total = 1 // Avoid zero denominator.
  	}
  	return 100.0 * float64(covered) / float64(total)
  }
  

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