internal/lsp: move the fixup and parallel limits into the main parse function

Previously these were only applied from inside parseFiles, which also made it
harder to refactor the remaining parse logic.
This theoretically means fixup is now called in more places than it was before,
but should cause no change in behaviour.

Change-Id: Ic6d006c1d36daca7514626653aaedf90d76e1d0f
Reviewed-on: https://go-review.googlesource.com/c/tools/+/181544
Run-TryBot: Ian Cottrell <iancottrell@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rebecca Stambler <rstambler@golang.org>

internal/lsp/cache/parse.go

@@ -21,6 +21,9 @@ import (
 	"golang.org/x/tools/internal/span"
 )
 
+// Limits the number of parallel parser calls per process.
+var parseLimit = make(chan bool, 20)
+
 type parseKey struct {
 	file source.FileIdentity
 	mode source.ParseMode
@@ -38,10 +41,6 @@ type parseGoData struct {
 	err error
 }
 
-// We use a counting semaphore to limit
-// the number of parallel I/O calls per process.
-var ioLimit = make(chan bool, 20)
-
 func (c *cache) ParseGo(fh source.FileHandle, mode source.ParseMode) source.ParseGoHandle {
 	key := parseKey{
 		file: fh.Identity(),
@@ -79,19 +78,24 @@ func parseGo(ctx context.Context, c *cache, fh source.FileHandle, mode source.Pa
 	if err != nil {
 		return nil, err
 	}
+	parseLimit <- true
+	defer func() { <-parseLimit }()
 	parserMode := parser.AllErrors | parser.ParseComments
 	if mode == source.ParseHeader {
 		parserMode = parser.ImportsOnly
 	}
 	ast, err := parser.ParseFile(c.fset, fh.Identity().URI.Filename(), buf, parserMode)
-	if err != nil {
-		return ast, err
+	if ast != nil {
+		if mode == source.ParseExported {
+			trimAST(ast)
+		}
+		// Fix any badly parsed parts of the AST.
+		tok := c.fset.File(ast.Pos())
+		if err := fix(ctx, ast, tok, buf); err != nil {
+			//TODO: we should do something with the error, but we have no access to a logger in here
+		}
 	}
-	if mode == source.ParseExported {
-		trimAST(ast)
-	}
-	//TODO: move the ast fixup code into here
-	return ast, nil
+	return ast, err
 }
 
 // parseFiles reads and parses the Go source files and returns the ASTs
@@ -109,7 +113,6 @@ func (imp *importer) parseFiles(filenames []string, ignoreFuncBodies bool) ([]*a
 		errors = make([]error, n)
 	)
 	// TODO: change this function to return the handles
-	// TODO: eliminate the wait group at this layer, it should be done in the parser
 	for i, filename := range filenames {
 		if err := imp.ctx.Err(); err != nil {
 			return nil, nil, err
@@ -125,11 +128,7 @@ func (imp *importer) parseFiles(filenames []string, ignoreFuncBodies bool) ([]*a
 		// now read and parse in parallel
 		wg.Add(1)
 		go func(i int, filename string) {
-			ioLimit <- true // wait
-			defer func() {
-				<-ioLimit // signal done
-				wg.Done()
-			}()
+			defer wg.Done()
 			// ParseFile may return a partial AST and an error.
 			f, err := ph.Parse(imp.ctx)
 			parsed[i], errors[i] = &astFile{
@@ -137,15 +136,6 @@ func (imp *importer) parseFiles(filenames []string, ignoreFuncBodies bool) ([]*a
 				err:       err,
 				isTrimmed: ignoreFuncBodies,
 			}, err
-			// TODO: move fixup into the parse function
-			// Fix any badly parsed parts of the AST.
-			if f != nil {
-				tok := imp.fset.File(f.Pos())
-				src, _, err := fh.Read(imp.ctx)
-				if err == nil {
-					imp.view.fix(imp.ctx, f, tok, src)
-				}
-			}
 		}(i, filename)
 	}
 	wg.Wait()
@@ -234,16 +224,17 @@ func isEllipsisArray(n ast.Expr) bool {
 
 // fix inspects and potentially modifies any *ast.BadStmts or *ast.BadExprs in the AST.
 // We attempt to modify the AST such that we can type-check it more effectively.
-func (v *view) fix(ctx context.Context, file *ast.File, tok *token.File, src []byte) {
+func fix(ctx context.Context, file *ast.File, tok *token.File, src []byte) error {
 	var parent ast.Node
+	var err error
 	ast.Inspect(file, func(n ast.Node) bool {
 		if n == nil {
 			return false
 		}
 		switch n := n.(type) {
 		case *ast.BadStmt:
-			if err := v.parseDeferOrGoStmt(n, parent, tok, src); err != nil {
-				v.Session().Logger().Debugf(ctx, "unable to parse defer or go from *ast.BadStmt: %v", err)
+			if err := parseDeferOrGoStmt(n, parent, tok, src); err != nil {
+				err = fmt.Errorf("unable to parse defer or go from *ast.BadStmt: %v", err)
 			}
 			return false
 		default:
@@ -251,6 +242,7 @@ func (v *view) fix(ctx context.Context, file *ast.File, tok *token.File, src []b
 			return true
 		}
 	})
+	return err
 }
 
 // parseDeferOrGoStmt tries to parse an *ast.BadStmt into a defer or a go statement.
@@ -260,7 +252,7 @@ func (v *view) fix(ctx context.Context, file *ast.File, tok *token.File, src []b
 // 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 (v *view) parseDeferOrGoStmt(bad *ast.BadStmt, parent ast.Node, tok *token.File, src []byte) error {
+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)
@@ -325,7 +317,7 @@ FindTo:
 	}
 	// parser.ParseExpr returns undefined positions.
 	// Adjust them for the current file.
-	v.offsetPositions(expr, from-1)
+	offsetPositions(expr, from-1)
 
 	// Package the expression into a fake *ast.CallExpr and re-insert into the function.
 	call := &ast.CallExpr{
@@ -353,7 +345,7 @@ FindTo:
 
 // offsetPositions applies an offset to the positions in an ast.Node.
 // TODO(rstambler): Add more cases here as they become necessary.
-func (v *view) offsetPositions(expr ast.Expr, offset token.Pos) {
+func offsetPositions(expr ast.Expr, offset token.Pos) {
 	ast.Inspect(expr, func(n ast.Node) bool {
 		switch n := n.(type) {
 		case *ast.Ident: