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// Copyright 2019 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 cache
import (
"bytes"
"context"
"go/ast"
"go/parser"
"go/scanner"
"go/token"
"reflect"
"golang.org/x/tools/internal/lsp/protocol"
"golang.org/x/tools/internal/lsp/source"
"golang.org/x/tools/internal/lsp/telemetry"
"golang.org/x/tools/internal/memoize"
"golang.org/x/tools/internal/span"
"golang.org/x/tools/internal/telemetry/log"
"golang.org/x/tools/internal/telemetry/trace"
errors "golang.org/x/xerrors"
)
// Limits the number of parallel parser calls per process.
var parseLimit = make(chan struct{}, 20)
// parseKey uniquely identifies a parsed Go file.
type parseKey struct {
file source.FileIdentity
mode source.ParseMode
}
type parseGoHandle struct {
handle *memoize.Handle
file source.FileHandle
mode source.ParseMode
}
type parseGoData struct {
memoize.NoCopy
ast *ast.File
parseError error // errors associated with parsing the file
mapper *protocol.ColumnMapper
err error
}
func (c *cache) ParseGoHandle(fh source.FileHandle, mode source.ParseMode) source.ParseGoHandle {
key := parseKey{
file: fh.Identity(),
mode: mode,
}
h := c.store.Bind(key, func(ctx context.Context) interface{} {
data := &parseGoData{}
data.ast, data.mapper, data.parseError, data.err = parseGo(ctx, c, fh, mode)
return data
})
return &parseGoHandle{
handle: h,
file: fh,
mode: mode,
}
}
func (h *parseGoHandle) File() source.FileHandle {
return h.file
}
func (h *parseGoHandle) Mode() source.ParseMode {
return h.mode
}
func (h *parseGoHandle) Parse(ctx context.Context) (*ast.File, *protocol.ColumnMapper, error, error) {
v := h.handle.Get(ctx)
if v == nil {
return nil, nil, nil, ctx.Err()
}
data := v.(*parseGoData)
return data.ast, data.mapper, data.parseError, data.err
}
func (h *parseGoHandle) Cached(ctx context.Context) (*ast.File, *protocol.ColumnMapper, error, error) {
v := h.handle.Cached()
if v == nil {
return nil, nil, nil, errors.Errorf("no cached AST for %s", h.file.Identity().URI)
}
data := v.(*parseGoData)
return data.ast, data.mapper, data.parseError, data.err
}
func hashParseKey(ph source.ParseGoHandle) string {
b := bytes.NewBuffer(nil)
b.WriteString(ph.File().Identity().String())
b.WriteString(string(ph.Mode()))
return hashContents(b.Bytes())
}
func hashParseKeys(phs []source.ParseGoHandle) string {
b := bytes.NewBuffer(nil)
for _, ph := range phs {
b.WriteString(hashParseKey(ph))
}
return hashContents(b.Bytes())
}
func parseGo(ctx context.Context, c *cache, fh source.FileHandle, mode source.ParseMode) (file *ast.File, mapper *protocol.ColumnMapper, parseError error, err error) {
ctx, done := trace.StartSpan(ctx, "cache.parseGo", telemetry.File.Of(fh.Identity().URI.Filename()))
defer done()
buf, _, err := fh.Read(ctx)
if err != nil {
return nil, nil, nil, err
}
parseLimit <- struct{}{}
defer func() { <-parseLimit }()
parserMode := parser.AllErrors | parser.ParseComments
if mode == source.ParseHeader {
parserMode = parser.ImportsOnly | parser.ParseComments
}
file, parseError = parser.ParseFile(c.fset, fh.Identity().URI.Filename(), buf, parserMode)
if file != nil {
if mode == source.ParseExported {
trimAST(file)
}
// Fix any badly parsed parts of the AST.
tok := c.fset.File(file.Pos())
if err := fix(ctx, file, tok, buf); err != nil {
log.Error(ctx, "failed to fix AST", err)
}
}
if file == nil {
// If the file is nil only due to parse errors,
// the parse errors are the actual errors.
err := parseError
if err == nil {
err = errors.Errorf("no AST for %s", fh.Identity().URI)
}
return nil, nil, parseError, err
}
tok := c.FileSet().File(file.Pos())
if tok == nil {
return nil, nil, parseError, errors.Errorf("no token.File for %s", fh.Identity().URI)
}
uri := fh.Identity().URI
content, _, err := fh.Read(ctx)
if err != nil {
return nil, nil, parseError, err
}
m := &protocol.ColumnMapper{
URI: uri,
Converter: span.NewTokenConverter(c.FileSet(), tok),
Content: content,
}
return file, m, parseError, nil
}
// trimAST clears any part of the AST not relevant to type checking
// expressions at pos.
func trimAST(file *ast.File) {
ast.Inspect(file, func(n ast.Node) bool {
if n == nil {
return false
}
switch n := n.(type) {
case *ast.FuncDecl:
n.Body = nil
case *ast.BlockStmt:
n.List = nil
case *ast.CaseClause:
n.Body = nil
case *ast.CommClause:
n.Body = nil
case *ast.CompositeLit:
// Leave elts in place for [...]T
// array literals, because they can
// affect the expression's type.
if !isEllipsisArray(n.Type) {
n.Elts = nil
}
}
return true
})
}
func isEllipsisArray(n ast.Expr) bool {
at, ok := n.(*ast.ArrayType)
if !ok {
return false
}
_, ok = at.Len.(*ast.Ellipsis)
return ok
}
// fix inspects the AST and potentially modifies any *ast.BadStmts so that it can be
// type-checked more effectively.
func fix(ctx context.Context, n ast.Node, tok *token.File, src []byte) error {
var (
ancestors []ast.Node
err error
)
ast.Inspect(n, func(n ast.Node) bool {
if n == nil {
if len(ancestors) > 0 {
ancestors = ancestors[:len(ancestors)-1]
}
return false
}
switch n := n.(type) {
case *ast.BadStmt:
var parent ast.Node
if len(ancestors) > 0 {
parent = ancestors[len(ancestors)-1]
}
err = parseDeferOrGoStmt(n, parent, tok, src) // don't shadow err
if err == nil {
// Recursively fix any BadStmts in our fixed node.
err = fix(ctx, parent, tok, src)
} else {
err = errors.Errorf("unable to parse defer or go from *ast.BadStmt: %v", err)
}
return false
default:
ancestors = append(ancestors, n)
return true
}
})
return err
}
// parseDeferOrGoStmt tries to parse an *ast.BadStmt into a defer or a go statement.
//
// go/parser packages a statement of the form "defer x." as an *ast.BadStmt because
// it does not include a call expression. This means that go/types skips type-checking
// this statement entirely, and we can't use the type information when completing.
// Here, we try to generate a fake *ast.DeferStmt or *ast.GoStmt to put into the AST,
// instead of the *ast.BadStmt.
func parseDeferOrGoStmt(bad *ast.BadStmt, parent ast.Node, tok *token.File, src []byte) error {
// Check if we have a bad statement containing either a "go" or "defer".
s := &scanner.Scanner{}
s.Init(tok, src, nil, 0)
var (
pos token.Pos
tkn token.Token
)
for {
if tkn == token.EOF {
return errors.Errorf("reached the end of the file")
}
if pos >= bad.From {
break
}
pos, tkn, _ = s.Scan()
}
var stmt ast.Stmt
switch tkn {
case token.DEFER:
stmt = &ast.DeferStmt{
Defer: pos,
}
case token.GO:
stmt = &ast.GoStmt{
Go: pos,
}
default:
return errors.Errorf("no defer or go statement found")
}
var (
from, to, last token.Pos
lastToken token.Token
braceDepth int
phantomSelectors []token.Pos
)
FindTo:
for {
to, tkn, _ = s.Scan()
if from == token.NoPos {
from = to
}
switch tkn {
case token.EOF:
break FindTo
case token.SEMICOLON:
// If we aren't in nested braces, end of statement means
// end of expression.
if braceDepth == 0 {
break FindTo
}
case token.LBRACE:
braceDepth++
}
// This handles the common dangling selector case. For example in
//
// defer fmt.
// y := 1
//
// we notice the dangling period and end our expression.
//
// If the previous token was a "." and we are looking at a "}",
// the period is likely a dangling selector and needs a phantom
// "_". Likewise if the current token is on a different line than
// the period, the period is likely a dangling selector.
if lastToken == token.PERIOD && (tkn == token.RBRACE || tok.Line(to) > tok.Line(last)) {
// Insert phantom "_" selector after the dangling ".".
phantomSelectors = append(phantomSelectors, last+1)
// If we aren't in a block then end the expression after the ".".
if braceDepth == 0 {
to = last + 1
break
}
}
lastToken = tkn
last = to
switch tkn {
case token.RBRACE:
braceDepth--
if braceDepth <= 0 {
if braceDepth == 0 {
// +1 to include the "}" itself.
to += 1
}
break FindTo
}
}
}
if !from.IsValid() || tok.Offset(from) >= len(src) {
return errors.Errorf("invalid from position")
}
if !to.IsValid() || tok.Offset(to) >= len(src) {
return errors.Errorf("invalid to position %d", to)
}
// Insert any phantom selectors needed to prevent dangling "." from messing
// up the AST.
exprBytes := make([]byte, 0, int(to-from)+len(phantomSelectors))
for i, b := range src[tok.Offset(from):tok.Offset(to)] {
if len(phantomSelectors) > 0 && from+token.Pos(i) == phantomSelectors[0] {
exprBytes = append(exprBytes, '_')
phantomSelectors = phantomSelectors[1:]
}
exprBytes = append(exprBytes, b)
}
if len(phantomSelectors) > 0 {
exprBytes = append(exprBytes, '_')
}
// Wrap our expression to make it a valid Go file we can pass to ParseFile.
fileSrc := bytes.Join([][]byte{
[]byte("package fake;func _(){"),
exprBytes,
[]byte("}"),
}, nil)
// Use ParseFile instead of ParseExpr because ParseFile has
// best-effort behavior, whereas ParseExpr fails hard on any error.
fakeFile, err := parser.ParseFile(token.NewFileSet(), "", fileSrc, 0)
if fakeFile == nil {
return errors.Errorf("error reading fake file source: %v", err)
}
// Extract our expression node from inside the fake file.
if len(fakeFile.Decls) == 0 {
return errors.Errorf("error parsing fake file: %v", err)
}
fakeDecl, _ := fakeFile.Decls[0].(*ast.FuncDecl)
if fakeDecl == nil || len(fakeDecl.Body.List) == 0 {
return errors.Errorf("no statement in %s: %v", exprBytes, err)
}
exprStmt, ok := fakeDecl.Body.List[0].(*ast.ExprStmt)
if !ok {
return errors.Errorf("no expr in %s: %v", exprBytes, err)
}
expr := exprStmt.X
// parser.ParseExpr returns undefined positions.
// Adjust them for the current file.
offsetPositions(expr, from-1-(expr.Pos()-1))
// Package the expression into a fake *ast.CallExpr and re-insert
// into the function.
call := &ast.CallExpr{
Fun: expr,
Lparen: to,
Rparen: to,
}
switch stmt := stmt.(type) {
case *ast.DeferStmt:
stmt.Call = call
case *ast.GoStmt:
stmt.Call = call
}
if !replaceNode(parent, bad, stmt) {
return errors.Errorf("couldn't replace %T in %T", stmt, parent)
}
return nil
}
var tokenPosType = reflect.TypeOf(token.NoPos)
// offsetPositions applies an offset to the positions in an ast.Node.
func offsetPositions(expr ast.Expr, offset token.Pos) {
ast.Inspect(expr, func(n ast.Node) bool {
if n == nil {
return false
}
v := reflect.ValueOf(n).Elem()
switch v.Kind() {
case reflect.Struct:
for i := 0; i < v.NumField(); i++ {
f := v.Field(i)
if f.Type() != tokenPosType {
continue
}
if !f.CanSet() {
continue
}
f.SetInt(int64(f.Interface().(token.Pos) + offset))
}
}
return true
})
}
// replaceNode updates parent's child oldChild to be newChild. It
// retuns whether it replaced successfully.
func replaceNode(parent, oldChild, newChild ast.Node) bool {
if parent == nil || oldChild == nil || newChild == nil {
return false
}
parentVal := reflect.ValueOf(parent).Elem()
if parentVal.Kind() != reflect.Struct {
return false
}
newChildVal := reflect.ValueOf(newChild)
tryReplace := func(v reflect.Value) bool {
if !v.CanSet() || !v.CanInterface() {
return false
}
// If the existing value is oldChild, we found our child. Make
// sure our newChild is assignable and then make the swap.
if v.Interface() == oldChild && newChildVal.Type().AssignableTo(v.Type()) {
v.Set(newChildVal)
return true
}
return false
}
// Loop over parent's struct fields.
for i := 0; i < parentVal.NumField(); i++ {
f := parentVal.Field(i)
switch f.Kind() {
// Check interface and pointer fields.
case reflect.Interface, reflect.Ptr:
if tryReplace(f) {
return true
}
// Search through any slice fields.
case reflect.Slice:
for i := 0; i < f.Len(); i++ {
if tryReplace(f.Index(i)) {
return true
}
}
}
}
return false
}