internal/lsp: absolutize paths when converting filenames to URIs

Fixes golang/go#30280

Change-Id: I95e72c8d952ce7d64114772e9ef3df6568ae5dd4
Reviewed-on: https://go-review.googlesource.com/c/163160
Run-TryBot: Rebecca Stambler <[email protected]>
TryBot-Result: Gobot Gobot <[email protected]>
Reviewed-by: Ian Cottrell <[email protected]>

Author: stamblerre

internal/lsp/cmd/definition.go

@@ -67,6 +67,9 @@ func (d *definition) Run(ctx context.Context, args ...string) error {
 	}
 	tok := f.GetToken()
 	pos := tok.Pos(from.Start.Offset)
+	if !pos.IsValid() {
+		return fmt.Errorf("invalid position %v", from.Start.Offset)
+	}
 	ident, err := source.Identifier(ctx, view, f, pos)
 	if err != nil {
 		return err

internal/lsp/cmd/location.go

@@ -7,6 +7,7 @@ package cmd
 import (
 	"fmt"
 	"go/token"
+	"path/filepath"
 	"regexp"
 	"strconv"
 
@@ -98,6 +99,9 @@ func parseLocation(value string) (Location, error) {
 		return loc, fmt.Errorf("bad location syntax %q", value)
 	}
 	loc.Filename = m[posReFile]
+	if !filepath.IsAbs(loc.Filename) {
+		loc.Filename, _ = filepath.Abs(loc.Filename) // ignore error
+	}
 	if m[posReSLine] != "" {
 		v, err := strconv.ParseInt(m[posReSLine], 10, 32)
 		if err != nil {