error when spec.json does not match generated name

pkg/spec/spec.go

@@ -2,6 +2,7 @@ package spec
 
 import (
 	"encoding/json"
+	"fmt"
 	"io/ioutil"
 	"os"
 	"path/filepath"
@@ -50,6 +51,10 @@ func Parse(data []byte, name string) (*v1alpha1.Config, error) {
 		return nil, errors.Wrap(err, "parsing spec.json")
 	}
 
+	// only allow explicit metadata.name when matching generated value
+	if config.Metadata.Name != "" && config.Metadata.Name != name {
+		return nil, fmt.Errorf("invalid metadata.name, must match generated %q", name)
+	}
 	// set the name field
 	config.Metadata.Name = name
 

pkg/tanka/parse_test.go

@@ -43,20 +43,29 @@ func TestEvalJsonnet(t *testing.T) {
 
 func TestEval(t *testing.T) {
 	cases := []struct {
-		baseDir  string
-		expected interface{}
+		baseDir       string
+		expectedError string
+		expected      interface{}
 	}{
 		{
-			baseDir: "./testdata/cases/env/",
+			baseDir:       "./testdata/cases/env-mismatch",
+			expectedError: `reading spec.json: invalid metadata.name, must match generated "cases/env-mismatch"`,
+		},
+		{
+			baseDir: "./testdata/cases/env",
 			expected: map[string]interface{}{
-				"tkName": "custom-name",
+				"tkName": "cases/env",
 			},
 		},
 	}
 
 	for _, test := range cases {
 		raw, _, e := eval(test.baseDir, jsonnet.Opts{})
-		assert.NoError(t, e)
-		assert.Equal(t, test.expected, raw)
+		if test.expectedError != "" {
+			assert.Equal(t, test.expectedError, e.Error())
+		} else {
+			assert.NoError(t, e)
+			assert.Equal(t, test.expected, raw)
+		}
 	}
 }

pkg/tanka/testdata/cases/env-mismatch/main.jsonnet

@@ -0,0 +1,5 @@
+local tk = (import "tk");
+
+{
+  tkName: tk.env.metadata.name,
+}

pkg/tanka/testdata/cases/env-mismatch/spec.json

@@ -0,0 +1,7 @@
+{
+  "apiVersion": "v1alpha1",
+  "kind": "Environment",
+  "metadata": {
+    "name": "mismatched-name"
+  }
+}

pkg/tanka/testdata/cases/env/spec.json

@@ -2,6 +2,6 @@
   "apiVersion": "v1alpha1",
   "kind": "Environment",
   "metadata": {
-    "name": "custom-name"
+    "name": "cases/env"
   }
 }