internal/lsp/fake: check for file changes after running the Go command

Our fake.Workdir generates synthetic file events for "watched" files
when using its file API, but we have no such hooks for file changes
originating from an external process, in this case the go command.

Previously, we detected a file event by checking go command logs to see
if a go.mod file was created. This is bound to be fragile, so we replace
this with a helper function that walks the working directory looking for
changes.

Change-Id: I2c2176099b97f3a3b25f4aed2b18de13ae05544a
Reviewed-on: https://go-review.googlesource.com/c/tools/+/232637
Run-TryBot: Robert Findley <[email protected]>
TryBot-Result: Gobot Gobot <[email protected]>
Reviewed-by: Rebecca Stambler <[email protected]>

Author: findleyr

internal/lsp/fake/sandbox.go

@@ -13,7 +13,6 @@ import (
 	"strings"
 
 	"golang.org/x/tools/internal/gocommand"
-	"golang.org/x/tools/internal/lsp/protocol"
 	"golang.org/x/tools/txtar"
 )
 
@@ -121,21 +120,14 @@ func (sb *Sandbox) RunGoCommand(ctx context.Context, verb string, args ...string
 		Env:        sb.GoEnv(),
 	}
 	gocmdRunner := &gocommand.Runner{}
-	_, stderr, _, err := gocmdRunner.RunRaw(ctx, inv)
+	_, _, _, err := gocmdRunner.RunRaw(ctx, inv)
 	if err != nil {
 		return err
 	}
-	// Hardcoded "file watcher": If the command executed was "go mod init",
-	// send a file creation event for a go.mod in the working directory.
-	if strings.HasPrefix(stderr.String(), "go: creating new go.mod") {
-		modpath := filepath.Join(sb.Workdir.workdir, "go.mod")
-		sb.Workdir.sendEvents(ctx, []FileEvent{{
-			Path: modpath,
-			ProtocolEvent: protocol.FileEvent{
-				URI:  toURI(modpath),
-				Type: protocol.Created,
-			},
-		}})
+	// Since running a go command may result in changes to workspace files,
+	// check if we need to send any any "watched" file events.
+	if err := sb.Workdir.CheckForFileChanges(ctx); err != nil {
+		return fmt.Errorf("checking for file changes: %w", err)
 	}
 	return nil
 }