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parse.go
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parse.go
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// Package discover implements trimming of ASTs based on test coverage,
// to aid in conceptualizing large code bases.
//
// It is based on the idea presented by Alan Shreve in his talk on
// conceptualizing large software systems, held at dotGo 2015 in Paris.
package discover
import (
"fmt"
"go/ast"
"go/build"
"go/parser"
"go/token"
"path/filepath"
"golang.org/x/tools/cover"
)
// Profile contains a map of statements and funcs that were covered
// by the cover profiles. It supports using the information to trim
// an AST down to the nodes that were actually reached.
type Profile struct {
Stmts map[ast.Stmt]bool
Funcs map[*ast.FuncDecl]bool
ImportPaths map[*ast.File]string
Files []*ast.File
Fset *token.FileSet
}
// ParseProfile parses a set of coverage profiles to produce a *Profile.
func ParseProfile(profs []*cover.Profile) (*Profile, error) {
profile := &Profile{
Stmts: make(map[ast.Stmt]bool),
Funcs: make(map[*ast.FuncDecl]bool),
ImportPaths: make(map[*ast.File]string),
Fset: token.NewFileSet(),
}
for _, prof := range profs {
file, importPath, err := findFile(prof.FileName)
if err != nil {
return nil, err
}
f, funcs, stmts, err := findFuncs(profile.Fset, file)
if err != nil {
return nil, err
}
profile.Files = append(profile.Files, f)
profile.ImportPaths[f] = importPath
blocks := prof.Blocks
for len(funcs) > 0 {
f := funcs[0]
for i, b := range blocks {
if b.StartLine > f.endLine || (b.StartLine == f.endLine && b.StartCol >= f.endCol) {
// Past the end of the func
funcs = funcs[1:]
blocks = blocks[i:]
break
}
if b.EndLine < f.startLine || (b.EndLine == f.startLine && b.EndCol <= f.startCol) {
// Before the beginning of the func
continue
}
if b.Count > 0 {
profile.Funcs[f.decl] = true
}
funcs = funcs[1:]
break
}
}
blocks = prof.Blocks // reset to all blocks
for len(stmts) > 0 {
s := stmts[0]
for i, b := range blocks {
if b.StartLine > s.endLine || (b.StartLine == s.endLine && b.StartCol >= s.endCol) {
// Past the end of the statement
stmts = stmts[1:]
blocks = blocks[i:]
break
}
if b.EndLine < s.startLine || (b.EndLine == s.startLine && b.EndCol <= s.startCol) {
// Before the beginning of the statement
continue
}
if b.Count > 0 {
profile.Stmts[s.stmt] = true
}
stmts = stmts[1:]
break
}
}
}
return profile, nil
}
// findFile tries to find the full path to a file, by looking in $GOROOT
// and $GOPATH.
func findFile(file string) (filename, pkgPath string, err error) {
dir, file := filepath.Split(file)
if dir != "" {
dir = dir[:len(dir)-1] // drop trailing '/'
}
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), pkg.ImportPath, nil
}
// findFuncs parses the file and returns a slice of FuncExtent descriptors.
func findFuncs(fset *token.FileSet, name string) (*ast.File, []*funcExtent, []*stmtExtent, error) {
parsedFile, err := parser.ParseFile(fset, name, nil, parser.ParseComments)
if err != nil {
return nil, nil, nil, err
}
visitor := &funcVisitor{fset: fset}
ast.Walk(visitor, parsedFile)
return parsedFile, visitor.funcs, visitor.stmts, nil
}
// funcExtent describes a function's extent in the source by file and position.
type funcExtent struct {
decl *ast.FuncDecl
name string
startLine int
startCol int
endLine int
endCol int
}
// stmtExtent describes a statement's extent in the source by file and position.
type stmtExtent struct {
stmt ast.Stmt
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
funcs []*funcExtent
stmts []*stmtExtent
}
// Visit implements the ast.Visitor interface.
func (v *funcVisitor) Visit(node ast.Node) ast.Visitor {
if f, ok := node.(*ast.FuncDecl); ok {
start := v.fset.Position(f.Pos())
end := v.fset.Position(f.End())
fe := &funcExtent{
decl: f,
startLine: start.Line,
startCol: start.Column,
endLine: end.Line,
endCol: end.Column,
}
v.funcs = append(v.funcs, fe)
} else if s, ok := node.(ast.Stmt); ok {
start, end := v.fset.Position(s.Pos()), v.fset.Position(s.End())
se := &stmtExtent{
stmt: s,
startLine: start.Line,
startCol: start.Column,
endLine: end.Line,
endCol: end.Column,
}
v.stmts = append(v.stmts, se)
}
return v
}