internal/lsp: handle common nil pointer exceptions

We may encounter these nil pointer if go/packages cannot find the
package of the given file, for example, when the user creates a new file
or a new package.

Change-Id: I16993017243a56332dd9f7e0aaf3c1d57f20fc3a
Reviewed-on: https://go-review.googlesource.com/c/tools/+/167462
Run-TryBot: Rebecca Stambler <rstambler@golang.org>
Reviewed-by: Ian Cottrell <iancottrell@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

internal/lsp/format.go

@@ -2,6 +2,7 @@ package lsp
 
 import (
 	"context"
+	"fmt"
 
 	"golang.org/x/tools/internal/lsp/protocol"
 	"golang.org/x/tools/internal/lsp/source"
@@ -16,8 +17,12 @@ func formatRange(ctx context.Context, v source.View, s span.Span) ([]protocol.Te
 	}
 	rng := s.Range(m.Converter)
 	if rng.Start == rng.End {
-		// if we have a single point, then assume the rest of the file
-		rng.End = f.GetToken(ctx).Pos(f.GetToken(ctx).Size())
+		// If we have a single point, assume we want the whole file.
+		tok := f.GetToken(ctx)
+		if tok == nil {
+			return nil, fmt.Errorf("no file information for %s", f.URI())
+		}
+		rng.End = tok.Pos(tok.Size())
 	}
 	edits, err := source.Format(ctx, f, rng)
 	if err != nil {
@@ -45,6 +50,10 @@ func newColumnMap(ctx context.Context, v source.View, uri span.URI) (source.File
 	if err != nil {
 		return nil, nil, err
 	}
-	m := protocol.NewColumnMapper(f.URI(), f.GetFileSet(ctx), f.GetToken(ctx), f.GetContent(ctx))
+	tok := f.GetToken(ctx)
+	if tok == nil {
+		return nil, nil, fmt.Errorf("no file information for %v", f.URI())
+	}
+	m := protocol.NewColumnMapper(f.URI(), f.GetFileSet(ctx), tok, f.GetContent(ctx))
 	return f, m, nil
 }

internal/lsp/imports.go

@@ -6,6 +6,7 @@ package lsp
 
 import (
 	"context"
+	"fmt"
 
 	"golang.org/x/tools/internal/lsp/protocol"
 	"golang.org/x/tools/internal/lsp/source"
@@ -19,8 +20,12 @@ func organizeImports(ctx context.Context, v source.View, s span.Span) ([]protoco
 	}
 	rng := s.Range(m.Converter)
 	if rng.Start == rng.End {
-		// if we have a single point, then assume the rest of the file
-		rng.End = f.GetToken(ctx).Pos(f.GetToken(ctx).Size())
+		// If we have a single point, assume we want the whole file.
+		tok := f.GetToken(ctx)
+		if tok == nil {
+			return nil, fmt.Errorf("no file information for %s", f.URI())
+		}
+		rng.End = tok.Pos(tok.Size())
 	}
 	edits, err := source.Imports(ctx, f, rng)
 	if err != nil {

internal/lsp/source/diagnostics.go

@@ -56,6 +56,9 @@ func Diagnostics(ctx context.Context, v View, uri span.URI) (map[span.URI][]Diag
 		return nil, err
 	}
 	pkg := f.GetPackage(ctx)
+	if pkg == nil {
+		return nil, fmt.Errorf("no package found for %v", f.URI())
+	}
 	// Prepare the reports we will send for this package.
 	reports := make(map[span.URI][]Diagnostic)
 	for _, filename := range pkg.GetFilenames() {
@@ -83,8 +86,12 @@ func Diagnostics(ctx context.Context, v View, uri span.URI) (map[span.URI][]Diag
 		if spn.IsPoint() && diag.Kind == packages.TypeError {
 			// Don't set a range if it's anything other than a type error.
 			if diagFile, err := v.GetFile(ctx, spn.URI); err == nil {
+				tok := diagFile.GetToken(ctx)
+				if tok == nil {
+					continue // ignore errors
+				}
 				content := diagFile.GetContent(ctx)
-				c := span.NewTokenConverter(diagFile.GetFileSet(ctx), diagFile.GetToken(ctx))
+				c := span.NewTokenConverter(diagFile.GetFileSet(ctx), tok)
 				s := spn.CleanOffset(c)
 				if end := bytes.IndexAny(content[s.Start.Offset:], " \n,():;[]"); end > 0 {
 					spn.End = s.Start