correctly list merge-request pipelines

The API endpoint seems to require a more precise payload when we attempt
to list merge-request based pipelines.

this should fix #280 and potentially #259

CHANGELOG.md

@@ -14,6 +14,7 @@ and this project adheres to [0ver](https://0ver.org) (more or less).
 ### Changed
 
 - Fixed the error handling when comparing 2 refs which resulted into nil pointer dereferences
+- Fixed the pulling of merge-request based pipelines
 - Bumped all dependencies
 
 ## [v0.4.9] - 2021-05-05

pkg/exporter/pipelines.go

@@ -36,13 +36,21 @@ func pullRefMetrics(ref schemas.Ref) error {
 		}
 	}
 
+	// We need a different syntax if the ref is a merge-request
+	var refName string
+	if ref.Kind == schemas.RefKindMergeRequest {
+		refName = fmt.Sprintf("refs/merge-requests/%s/head", ref.Name)
+	} else {
+		refName = ref.Name
+	}
+
 	pipelines, err := gitlabClient.GetProjectPipelines(ref.ProjectName, &goGitlab.ListProjectPipelinesOptions{
 		// We only need the most recent pipeline
 		ListOptions: goGitlab.ListOptions{
 			PerPage: 1,
 			Page:    1,
 		},
-		Ref: goGitlab.String(ref.Name),
+		Ref: &refName,
 	})
 	if err != nil {
 		return fmt.Errorf("error fetching project pipelines for %s: %v", ref.ProjectName, err)

pkg/exporter/pipelines_test.go

@@ -16,6 +16,7 @@ func TestPullRefMetricsSucceed(t *testing.T) {
 
 	mux.HandleFunc("/api/v4/projects/foo/pipelines",
 		func(w http.ResponseWriter, r *http.Request) {
+			assert.Equal(t, "bar", r.URL.Query().Get("ref"))
 			fmt.Fprint(w, `[{"id":1}]`)
 		})
 
@@ -87,6 +88,37 @@ func TestPullRefMetricsSucceed(t *testing.T) {
 }
 
 func TestPullRefMetricsMergeRequestPipeline(t *testing.T) {
+	resetGlobalValues()
+	mux, server := configureMockedGitlabClient()
+	defer server.Close()
+
+	mux.HandleFunc("/api/v4/projects/foo/pipelines",
+		func(w http.ResponseWriter, r *http.Request) {
+			assert.Equal(t, "refs/merge-requests/1234/head", r.URL.Query().Get("ref"))
+			fmt.Fprint(w, `[{"id":1}]`)
+		})
+
+	mux.HandleFunc("/api/v4/projects/foo/pipelines/1",
+		func(w http.ResponseWriter, r *http.Request) {
+			fmt.Fprint(w, `{"id":1,"updated_at":"2016-08-11T11:28:34.085Z","duration":300,"status":"running","coverage":"30.2"}`)
+		})
+
+	mux.HandleFunc(fmt.Sprintf("/api/v4/projects/foo/pipelines/1/variables"),
+		func(w http.ResponseWriter, r *http.Request) {
+			assert.Equal(t, "GET", r.Method)
+			fmt.Fprint(w, `[{"key":"foo","value":"bar"}]`)
+		})
+
+	// Metrics pull shall succeed
+	assert.NoError(t, pullRefMetrics(schemas.Ref{
+		Kind:                         schemas.RefKindMergeRequest,
+		ProjectName:                  "foo",
+		Name:                         "1234",
+		PullPipelineVariablesEnabled: true,
+	}))
+}
+
+func TestPullRefMetricsMergeRequestPipelineAlreadyLoaded(t *testing.T) {
 	resetGlobalValues()
 	ref := schemas.Ref{
 		Kind: schemas.RefKindMergeRequest,