More user-friendly error message if batch change name is invalid (#498)

* More user-friendly error message if batch change name is invalid

This fixes https://github.com/sourcegraph/sourcegraph/issues/16955.

* Add regression test for user-friendly error message

Author: mrnugget

internal/batches/batch_spec.go

@@ -2,6 +2,7 @@ package batches
 
 import (
 	"fmt"
+	"strings"
 
 	"github.com/gobwas/glob"
 	"github.com/hashicorp/go-multierror"
@@ -107,6 +108,21 @@ type Group struct {
 func ParseBatchSpec(data []byte, features featureFlags) (*BatchSpec, error) {
 	var spec BatchSpec
 	if err := yaml.UnmarshalValidate(schema.BatchSpecJSON, data, &spec); err != nil {
+		if multiErr, ok := err.(*multierror.Error); ok {
+			var newMultiError *multierror.Error
+
+			for _, e := range multiErr.Errors {
+				// In case of `name` we try to make the error message more user-friendly.
+				if strings.Contains(e.Error(), "name: Does not match pattern") {
+					newMultiError = multierror.Append(newMultiError, fmt.Errorf("The batch change name can only contain word characters, dots and dashes. No whitespace or newlines allowed."))
+				} else {
+					newMultiError = multierror.Append(newMultiError, e)
+				}
+			}
+
+			return nil, newMultiError.ErrorOrNil()
+		}
+
 		return nil, err
 	}
 

internal/batches/batch_spec_test.go

@@ -46,6 +46,41 @@ steps:
 		wantErr := `1 error occurred:
 	* batch spec includes steps but no changesetTemplate
 
+`
+		haveErr := err.Error()
+		if haveErr != wantErr {
+			t.Fatalf("wrong error. want=%q, have=%q", wantErr, haveErr)
+		}
+	})
+
+	t.Run("invalid batch change name", func(t *testing.T) {
+		const spec = `
+name: this name is invalid cause it contains whitespace
+description: Add Hello World to READMEs
+on:
+  - repositoriesMatchingQuery: file:README.md
+steps:
+  - run: echo Hello World | tee -a $(find -name README.md)
+    container: alpine:3
+changesetTemplate:
+  title: Hello World
+  body: My first batch change!
+  branch: hello-world
+  commit:
+    message: Append Hello World to all README.md files
+  published: false
+`
+
+		_, err := ParseBatchSpec([]byte(spec), featureFlags{})
+		if err == nil {
+			t.Fatal("no error returned")
+		}
+
+		// We expect this error to be user-friendly, which is why we test for
+		// it specifically here.
+		wantErr := `1 error occurred:
+	* The batch change name can only contain word characters, dots and dashes. No whitespace or newlines allowed.
+
 `
 		haveErr := err.Error()
 		if haveErr != wantErr {