fix: return better error if regexp is invalid

Signed-off-by: Miguel Ángel Ducanto Hadad <[email protected]>
(cherry picked from commit 7cadaa2)

fn.go

@@ -78,7 +78,11 @@ func (f *Function) RunFunction(_ context.Context, req *fnv1beta1.RunFunctionRequ
 					// possibly avoid using regex for matching literal strings
 					strictPattern = fmt.Sprintf("%s%s%s", START, string(before), END)
 				}
-				re := regexp.MustCompile(strictPattern)
+				re, err := regexp.Compile(strictPattern)
+				if err != nil {
+					response.Fatal(rsp, errors.Wrapf(err, "cannot compile regex %s", strictPattern))
+					return rsp, nil
+				}
 				keys := []resource.Name{}
 				for k := range desiredComposed {
 					if re.MatchString(string(k)) {

fn_test.go

@@ -786,7 +786,7 @@ func TestRunFunction(t *testing.T) {
 			},
 		},
 		"SequenceRegexAlreadyPrefixed": {
-			reason: "The function should delay the creation of second and fourth resources because the first and third are not ready",
+			reason: "The function should not modify the sequence regex, since it's already prefixed",
 			args: args{
 				req: &fnv1beta1.RunFunctionRequest{
 					Input: resource.MustStructObject(&v1beta1.Input{
@@ -865,6 +865,78 @@ func TestRunFunction(t *testing.T) {
 				},
 			},
 		},
+		"SequenceRegexInvalidRegex": {
+			reason: "The function should return a fatal error because the regex is invalid",
+			args: args{
+				req: &fnv1beta1.RunFunctionRequest{
+					Input: resource.MustStructObject(&v1beta1.Input{
+						Rules: []v1beta1.SequencingRule{
+							{
+								Sequence: []resource.Name{
+									`^(`,
+									"second",
+								},
+							},
+						},
+					}),
+					Observed: &fnv1beta1.State{
+						Composite: &fnv1beta1.Resource{
+							Resource: resource.MustStructJSON(xr),
+						},
+						Resources: map[string]*fnv1beta1.Resource{},
+					},
+					Desired: &fnv1beta1.State{
+						Composite: &fnv1beta1.Resource{
+							Resource: resource.MustStructJSON(xr),
+						},
+						Resources: map[string]*fnv1beta1.Resource{
+							"first-0": {
+								Resource: resource.MustStructJSON(mr),
+								Ready:    fnv1beta1.Ready_READY_TRUE,
+							},
+							"first-1": {
+								Resource: resource.MustStructJSON(mr),
+								Ready:    fnv1beta1.Ready_READY_TRUE,
+							},
+							"second": {
+								Resource: resource.MustStructJSON(mr),
+								Ready:    fnv1beta1.Ready_READY_TRUE,
+							},
+						},
+					},
+				},
+			},
+			want: want{
+				rsp: &fnv1beta1.RunFunctionResponse{
+					Meta: &fnv1beta1.ResponseMeta{Ttl: durationpb.New(response.DefaultTTL)},
+					Results: []*fnv1beta1.Result{
+						{
+							Severity: fnv1beta1.Severity_SEVERITY_FATAL,
+							Message:  "cannot compile regex ^(: error parsing regexp: missing closing ): `^(`",
+						},
+					},
+					Desired: &fnv1beta1.State{
+						Composite: &fnv1beta1.Resource{
+							Resource: resource.MustStructJSON(xr),
+						},
+						Resources: map[string]*fnv1beta1.Resource{
+							"first-0": {
+								Resource: resource.MustStructJSON(mr),
+								Ready:    fnv1beta1.Ready_READY_TRUE,
+							},
+							"first-1": {
+								Resource: resource.MustStructJSON(mr),
+								Ready:    fnv1beta1.Ready_READY_TRUE,
+							},
+							"second": {
+								Resource: resource.MustStructJSON(mr),
+								Ready:    fnv1beta1.Ready_READY_TRUE,
+							},
+						},
+					},
+				},
+			},
+		},
 	}
 
 	for name, tc := range cases {