fix: anchor cyclic detection (#30)

Closes #25

Reviewed-on: https://gitea.com/actions-oss/act-cli/pulls/30
Co-authored-by: Christopher Homberger <christopher.homberger@web.de>
Co-committed-by: Christopher Homberger <christopher.homberger@web.de>

pkg/model/anchors_test.go

@@ -7,29 +7,6 @@ import (
 	"gopkg.in/yaml.v3"
 )
 
-func TestVerifyCycleIsInvalid(t *testing.T) {
-	var node yaml.Node
-	err := yaml.Unmarshal([]byte(`
-a: &a
-  ref: *b
-
-b: &b
-  ref: *a
-`), &node)
-	assert.Error(t, err)
-}
-
-func TestVerifyCycleIsInvalid2(t *testing.T) {
-	var node yaml.Node
-	err := yaml.Unmarshal([]byte(`
-a: &a
-  ref: *a
-`), &node)
-	assert.NoError(t, err)
-	err = resolveAliases(&node)
-	assert.Error(t, err)
-}
-
 func TestVerifyNilAliasError(t *testing.T) {
 	var node yaml.Node
 	err := yaml.Unmarshal([]byte(`
@@ -44,3 +21,94 @@ test:
 	err = resolveAliases(&node)
 	assert.Error(t, err)
 }
+
+func TestVerifyNoRecursion(t *testing.T) {
+	table := []struct {
+		name      string
+		yaml      string
+		yamlErr   bool
+		anchorErr bool
+	}{
+		{
+			name: "no anchors",
+			yaml: `
+a: x
+b: y
+c: z
+`,
+			yamlErr:   false,
+			anchorErr: false,
+		},
+		{
+			name: "simple anchors",
+			yaml: `
+a: &a x
+b: &b y
+c: *a
+`,
+			yamlErr:   false,
+			anchorErr: false,
+		},
+		{
+			name: "nested anchors",
+			yaml: `
+a: &a
+  val: x
+b: &b
+  val: y
+c: *a
+`,
+			yamlErr:   false,
+			anchorErr: false,
+		},
+		{
+			name: "circular anchors",
+			yaml: `
+a: &b
+  ref: *c
+b: &c
+  ref: *b
+`,
+			yamlErr:   true,
+			anchorErr: false,
+		},
+		{
+			name: "self-referencing anchor",
+			yaml: `
+a: &a
+  ref: *a
+`,
+			yamlErr:   false,
+			anchorErr: true,
+		},
+		{
+			name: "reuse snippet with anchors",
+			yaml: `
+a: &b x
+b: &a
+   ref: *b
+c: *a
+`,
+			yamlErr:   false,
+			anchorErr: false,
+		},
+	}
+
+	for _, tt := range table {
+		t.Run(tt.name, func(t *testing.T) {
+			var node yaml.Node
+			err := yaml.Unmarshal([]byte(tt.yaml), &node)
+			if tt.yamlErr {
+				assert.Error(t, err)
+				return
+			}
+			assert.NoError(t, err)
+			err = resolveAliases(&node)
+			if tt.anchorErr {
+				assert.Error(t, err)
+			} else {
+				assert.NoError(t, err)
+			}
+		})
+	}
+}