internal/lsp: improve error handling while parsing

It the context is canceled (or times out) during parsing, we were
previously caching the package with no *ast.Files. Any further LSP
queries against that package would fail because the package is already
loaded, but none of the files are mapped to the package.

Fix by checking explicitly for context errors in parseFiles and
propagating them instead of continuing.

Author: muirdm

internal/lsp/cache/check.go

@@ -103,8 +103,18 @@ func (imp *importer) typeCheck(pkgPath string) (*pkg, error) {
 	// Don't type-check function bodies if we are not in the top-level package.
 	files, errs := imp.parseFiles(meta.files, imp.ignoreFuncBodies(pkg.pkgPath))
 	for _, err := range errs {
+		// Don't cache the package if we didn't finish parsing the files.
+		if err == context.Canceled || err == context.DeadlineExceeded {
+			return nil, err
+		}
 		appendError(err)
 	}
+
+	// If something unexpected happens, don't cache a package with 0 parsed files.
+	if len(files) == 0 {
+		return nil, fmt.Errorf("no parsed files for package %s", pkg.pkgPath)
+	}
+
 	pkg.syntax = files
 
 	// Handle circular imports by copying previously seen imports.

internal/lsp/cache/load.go

@@ -42,9 +42,12 @@ func (v *view) loadParseTypecheck(ctx context.Context, f *goFile) ([]packages.Er
 	}
 	// Type-check package.
 	pkg, err := imp.getPkg(f.meta.pkgPath)
-	if pkg == nil || pkg.IsIllTyped() {
+	if err != nil {
 		return nil, err
 	}
+	if pkg == nil || pkg.IsIllTyped() {
+		return nil, fmt.Errorf("loadParseTypecheck: %s is ill typed", f.meta.pkgPath)
+	}
 	// If we still have not found the package for the file, something is wrong.
 	if f.pkg == nil {
 		return nil, fmt.Errorf("parse: no package found for %v", f.filename())

internal/lsp/cache/parse.go

@@ -76,6 +76,7 @@ func (imp *importer) parseFiles(filenames []string, ignoreFuncBodies bool) ([]*a
 			// We don't have a cached AST for this file, so we read its content and parse it.
 			data, _, err := gof.Handle(imp.ctx).Read(imp.ctx)
 			if err != nil {
+				errors[i] = err
 				return
 			}
 			src := data