--- /dev/null
+// Copyright 2009 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.
+
+package main
+
+import (
+ "fmt"
+ "go/ast"
+ "go/parser"
+ "go/token"
+ "os"
+ "reflect"
+ "strings"
+ "unicode"
+ "unicode/utf8"
+)
+
+func initRewrite() {
+ if *rewriteRule == "" {
+ rewrite = nil // disable any previous rewrite
+ return
+ }
+ f := strings.Split(*rewriteRule, "->")
+ if len(f) != 2 {
+ fmt.Fprintf(os.Stderr, "rewrite rule must be of the form 'pattern -> replacement'\n")
+ os.Exit(2)
+ }
+ pattern := parseExpr(f[0], "pattern")
+ replace := parseExpr(f[1], "replacement")
+ rewrite = func(p *ast.File) *ast.File { return rewriteFile(pattern, replace, p) }
+}
+
+// parseExpr parses s as an expression.
+// It might make sense to expand this to allow statement patterns,
+// but there are problems with preserving formatting and also
+// with what a wildcard for a statement looks like.
+func parseExpr(s, what string) ast.Expr {
+ x, err := parser.ParseExpr(s)
+ if err != nil {
+ fmt.Fprintf(os.Stderr, "parsing %s %s at %s\n", what, s, err)
+ os.Exit(2)
+ }
+ return x
+}
+
+// Keep this function for debugging.
+/*
+func dump(msg string, val reflect.Value) {
+ fmt.Printf("%s:\n", msg)
+ ast.Print(fileSet, val.Interface())
+ fmt.Println()
+}
+*/
+
+// rewriteFile applies the rewrite rule 'pattern -> replace' to an entire file.
+func rewriteFile(pattern, replace ast.Expr, p *ast.File) *ast.File {
+ cmap := ast.NewCommentMap(fileSet, p, p.Comments)
+ m := make(map[string]reflect.Value)
+ pat := reflect.ValueOf(pattern)
+ repl := reflect.ValueOf(replace)
+
+ var rewriteVal func(val reflect.Value) reflect.Value
+ rewriteVal = func(val reflect.Value) reflect.Value {
+ // don't bother if val is invalid to start with
+ if !val.IsValid() {
+ return reflect.Value{}
+ }
+ val = apply(rewriteVal, val)
+ for k := range m {
+ delete(m, k)
+ }
+ if match(m, pat, val) {
+ val = subst(m, repl, reflect.ValueOf(val.Interface().(ast.Node).Pos()))
+ }
+ return val
+ }
+
+ r := apply(rewriteVal, reflect.ValueOf(p)).Interface().(*ast.File)
+ r.Comments = cmap.Filter(r).Comments() // recreate comments list
+ return r
+}
+
+// set is a wrapper for x.Set(y); it protects the caller from panics if x cannot be changed to y.
+func set(x, y reflect.Value) {
+ // don't bother if x cannot be set or y is invalid
+ if !x.CanSet() || !y.IsValid() {
+ return
+ }
+ defer func() {
+ if x := recover(); x != nil {
+ if s, ok := x.(string); ok &&
+ (strings.Contains(s, "type mismatch") || strings.Contains(s, "not assignable")) {
+ // x cannot be set to y - ignore this rewrite
+ return
+ }
+ panic(x)
+ }
+ }()
+ x.Set(y)
+}
+
+// Values/types for special cases.
+var (
+ objectPtrNil = reflect.ValueOf((*ast.Object)(nil))
+ scopePtrNil = reflect.ValueOf((*ast.Scope)(nil))
+
+ identType = reflect.TypeOf((*ast.Ident)(nil))
+ objectPtrType = reflect.TypeOf((*ast.Object)(nil))
+ positionType = reflect.TypeOf(token.NoPos)
+ callExprType = reflect.TypeOf((*ast.CallExpr)(nil))
+ scopePtrType = reflect.TypeOf((*ast.Scope)(nil))
+)
+
+// apply replaces each AST field x in val with f(x), returning val.
+// To avoid extra conversions, f operates on the reflect.Value form.
+func apply(f func(reflect.Value) reflect.Value, val reflect.Value) reflect.Value {
+ if !val.IsValid() {
+ return reflect.Value{}
+ }
+
+ // *ast.Objects introduce cycles and are likely incorrect after
+ // rewrite; don't follow them but replace with nil instead
+ if val.Type() == objectPtrType {
+ return objectPtrNil
+ }
+
+ // similarly for scopes: they are likely incorrect after a rewrite;
+ // replace them with nil
+ if val.Type() == scopePtrType {
+ return scopePtrNil
+ }
+
+ switch v := reflect.Indirect(val); v.Kind() {
+ case reflect.Slice:
+ for i := 0; i < v.Len(); i++ {
+ e := v.Index(i)
+ set(e, f(e))
+ }
+ case reflect.Struct:
+ for i := 0; i < v.NumField(); i++ {
+ e := v.Field(i)
+ set(e, f(e))
+ }
+ case reflect.Interface:
+ e := v.Elem()
+ set(v, f(e))
+ }
+ return val
+}
+
+func isWildcard(s string) bool {
+ rune, size := utf8.DecodeRuneInString(s)
+ return size == len(s) && unicode.IsLower(rune)
+}
+
+// match reports whether pattern matches val,
+// recording wildcard submatches in m.
+// If m == nil, match checks whether pattern == val.
+func match(m map[string]reflect.Value, pattern, val reflect.Value) bool {
+ // Wildcard matches any expression. If it appears multiple
+ // times in the pattern, it must match the same expression
+ // each time.
+ if m != nil && pattern.IsValid() && pattern.Type() == identType {
+ name := pattern.Interface().(*ast.Ident).Name
+ if isWildcard(name) && val.IsValid() {
+ // wildcards only match valid (non-nil) expressions.
+ if _, ok := val.Interface().(ast.Expr); ok && !val.IsNil() {
+ if old, ok := m[name]; ok {
+ return match(nil, old, val)
+ }
+ m[name] = val
+ return true
+ }
+ }
+ }
+
+ // Otherwise, pattern and val must match recursively.
+ if !pattern.IsValid() || !val.IsValid() {
+ return !pattern.IsValid() && !val.IsValid()
+ }
+ if pattern.Type() != val.Type() {
+ return false
+ }
+
+ // Special cases.
+ switch pattern.Type() {
+ case identType:
+ // For identifiers, only the names need to match
+ // (and none of the other *ast.Object information).
+ // This is a common case, handle it all here instead
+ // of recursing down any further via reflection.
+ p := pattern.Interface().(*ast.Ident)
+ v := val.Interface().(*ast.Ident)
+ return p == nil && v == nil || p != nil && v != nil && p.Name == v.Name
+ case objectPtrType, positionType:
+ // object pointers and token positions always match
+ return true
+ case callExprType:
+ // For calls, the Ellipsis fields (token.Position) must
+ // match since that is how f(x) and f(x...) are different.
+ // Check them here but fall through for the remaining fields.
+ p := pattern.Interface().(*ast.CallExpr)
+ v := val.Interface().(*ast.CallExpr)
+ if p.Ellipsis.IsValid() != v.Ellipsis.IsValid() {
+ return false
+ }
+ }
+
+ p := reflect.Indirect(pattern)
+ v := reflect.Indirect(val)
+ if !p.IsValid() || !v.IsValid() {
+ return !p.IsValid() && !v.IsValid()
+ }
+
+ switch p.Kind() {
+ case reflect.Slice:
+ if p.Len() != v.Len() {
+ return false
+ }
+ for i := 0; i < p.Len(); i++ {
+ if !match(m, p.Index(i), v.Index(i)) {
+ return false
+ }
+ }
+ return true
+
+ case reflect.Struct:
+ for i := 0; i < p.NumField(); i++ {
+ if !match(m, p.Field(i), v.Field(i)) {
+ return false
+ }
+ }
+ return true
+
+ case reflect.Interface:
+ return match(m, p.Elem(), v.Elem())
+ }
+
+ // Handle token integers, etc.
+ return p.Interface() == v.Interface()
+}
+
+// subst returns a copy of pattern with values from m substituted in place
+// of wildcards and pos used as the position of tokens from the pattern.
+// if m == nil, subst returns a copy of pattern and doesn't change the line
+// number information.
+func subst(m map[string]reflect.Value, pattern reflect.Value, pos reflect.Value) reflect.Value {
+ if !pattern.IsValid() {
+ return reflect.Value{}
+ }
+
+ // Wildcard gets replaced with map value.
+ if m != nil && pattern.Type() == identType {
+ name := pattern.Interface().(*ast.Ident).Name
+ if isWildcard(name) {
+ if old, ok := m[name]; ok {
+ return subst(nil, old, reflect.Value{})
+ }
+ }
+ }
+
+ if pos.IsValid() && pattern.Type() == positionType {
+ // use new position only if old position was valid in the first place
+ if old := pattern.Interface().(token.Pos); !old.IsValid() {
+ return pattern
+ }
+ return pos
+ }
+
+ // Otherwise copy.
+ switch p := pattern; p.Kind() {
+ case reflect.Slice:
+ if p.IsNil() {
+ // Do not turn nil slices into empty slices. go/ast
+ // guarantees that certain lists will be nil if not
+ // populated.
+ return reflect.Zero(p.Type())
+ }
+ v := reflect.MakeSlice(p.Type(), p.Len(), p.Len())
+ for i := 0; i < p.Len(); i++ {
+ v.Index(i).Set(subst(m, p.Index(i), pos))
+ }
+ return v
+
+ case reflect.Struct:
+ v := reflect.New(p.Type()).Elem()
+ for i := 0; i < p.NumField(); i++ {
+ v.Field(i).Set(subst(m, p.Field(i), pos))
+ }
+ return v
+
+ case reflect.Ptr:
+ v := reflect.New(p.Type()).Elem()
+ if elem := p.Elem(); elem.IsValid() {
+ v.Set(subst(m, elem, pos).Addr())
+ }
+ return v
+
+ case reflect.Interface:
+ v := reflect.New(p.Type()).Elem()
+ if elem := p.Elem(); elem.IsValid() {
+ v.Set(subst(m, elem, pos))
+ }
+ return v
+ }
+
+ return pattern
+}
projects / dotfiles / .git / blobdiff