lint: Match bare function calls

Currently `Matcher` will only match against selector expressions, e.g.
`fmt.Println`. A bare function call, e.g. `Println`, will not be
matched.

Update `Matcher` to handle both package qualified and bare function
calls.

Also, fix the test comment for `NewUnavailable` to include `want`. Prior
to updating `Matcher` this condition was not being tested and was
silently failing. We leave off the URL at the end of the report for ease
of matching, this was being interpreted as a regexp by the `analysis`
package and is a pain to escape properly.

2 files changed, 13 insertions, 4 deletions

diff --git a/tools/golangci-lint/gitaly/matcher.go b/tools/golangci-lint/gitaly/matcher.go
index 9b180a726..ec7620792 100644
--- a/tools/golangci-lint/gitaly/matcher.go
+++ b/tools/golangci-lint/gitaly/matcher.go
@@ -33,6 +33,8 @@ var funcNamePattern = regexp.MustCompile(`^\(?([^\\)].*)\)?\.(.*)$`)
 //     "gitlab.com/gitlab-org/gitaly/v15/internal/structerr.NewInternal",
 //   - A function of a struct inside a package:
 //     "(*gitlab.com/gitlab-org/gitaly/v15/internal/structerr.Error).Unwrap",
+//   - A local function call:
+//     "New(1)",
 //
 // This Matcher doesn't support interface match (yet).
 func (m *Matcher) MatchFunction(call *ast.CallExpr, rules []string) bool {
@@ -76,11 +78,18 @@ func (m *Matcher) functionName(call *ast.CallExpr) string {
 }
 
 func (m *Matcher) getFunction(call *ast.CallExpr) (*types.Func, bool) {
-	sel, ok := call.Fun.(*ast.SelectorExpr)
-	if !ok {
+	var ident *ast.Ident
+
+	switch ty := call.Fun.(type) {
+	case *ast.SelectorExpr:
+		ident = ty.Sel
+	case *ast.Ident:
+		ident = ty
+	default:
 		return nil, false
 	}
-	fn, ok := m.typesInfo.ObjectOf(sel.Sel).(*types.Func)
+
+	fn, ok := m.typesInfo.ObjectOf(ident).(*types.Func)
 	if !ok {
 		return nil, false
 	}
diff --git a/tools/golangci-lint/gitaly/testdata/src/unavailable_code/unavailable_code_test.go b/tools/golangci-lint/gitaly/testdata/src/unavailable_code/unavailable_code_test.go
index 5493e3f7a..b107aa4ae 100644
--- a/tools/golangci-lint/gitaly/testdata/src/unavailable_code/unavailable_code_test.go
+++ b/tools/golangci-lint/gitaly/testdata/src/unavailable_code/unavailable_code_test.go
@@ -17,5 +17,5 @@ func errorWrapOkay() {
 }
 
 func errorWrapNotOkay() {
-	_ = NewUnavailable("hello world") // please avoid using the Unavailable status code: https://gitlab.com/gitlab-org/gitaly/-/blob/master/STYLE.md?plain=0#unavailable-code
+	_ = NewUnavailable("hello world") // want "please avoid using the Unavailable status code.*"
 }