fix(internal/serviceconfig): return empty string when service config is not found (#3191)

Previously, `Find` returned an error when no service config YAML file
existed for an API path. This caused generation to fail for types-only
libraries like google-cloud-apps-script-type that don't have service
configs in googleapis.

`Find` now returns an empty string with no error when a service config
is not found. The sidekick parser already handles empty service configs
correctly, so this allows types-only libraries to generate successfully.

Author: julieqiu

internal/serviceconfig/serviceconfig.go

@@ -18,7 +18,6 @@ package serviceconfig
 import (
 	"bufio"
 	"encoding/json"
-	"errors"
 	"fmt"
 	"os"
 	"path/filepath"
@@ -41,8 +40,6 @@ type (
 	OAuthRequirements  = serviceconfig.OAuthRequirements
 )
 
-var errServiceConfigNotFound = errors.New("service config file not found")
-
 // Read reads a service config from a YAML file and returns it as a Service
 // proto. The file is parsed as YAML, converted to JSON, and then unmarshaled
 // into a Service proto.
@@ -108,7 +105,7 @@ func Find(googleapisDir, apiPath string) (string, error) {
 			return filepath.Join(apiPath, name), nil
 		}
 	}
-	return "", errServiceConfigNotFound
+	return "", nil
 }
 
 // isServiceConfigFile checks if the file contains "type: google.api.Service".

internal/serviceconfig/serviceconfig_test.go

@@ -15,7 +15,6 @@
 package serviceconfig
 
 import (
-	"errors"
 	"os"
 	"path/filepath"
 	"strings"
@@ -80,19 +79,40 @@ func TestNoGenprotoServiceConfigImports(t *testing.T) {
 }
 
 func TestFind(t *testing.T) {
-	got, err := Find("testdata/googleapis", "google/cloud/speech/v1")
-	if err != nil {
-		t.Fatal(err)
-	}
-	want := "google/cloud/speech/v1/speech_v1.yaml"
-	if got != want {
-		t.Errorf("got %q, want %q", got, want)
-	}
-}
-
-func TestFindThrowsErrorIfNotFound(t *testing.T) {
-	_, err := Find("testdata/googleapis", "google/cloud/compute/v1")
-	if !errors.Is(err, errServiceConfigNotFound) {
-		t.Errorf("Find() error = %v, want %v", err, errServiceConfigNotFound)
+	const googleapisDir = "testdata/googleapis"
+	for _, test := range []struct {
+		name    string
+		channel string
+		want    string
+		wantErr bool
+	}{
+		{
+			name:    "found",
+			channel: "google/cloud/speech/v1",
+			want:    "google/cloud/speech/v1/speech_v1.yaml",
+		},
+		{
+			name:    "not found",
+			channel: "google/cloud/compute/v1",
+			want:    "",
+		},
+		{
+			name:    "directory does not exist",
+			channel: "google/cloud/nonexistent/v1",
+			wantErr: true,
+		},
+	} {
+		t.Run(test.name, func(t *testing.T) {
+			got, err := Find(googleapisDir, test.channel)
+			if err != nil {
+				if !test.wantErr {
+					t.Fatal(err)
+				}
+				return
+			}
+			if got != test.want {
+				t.Errorf("Find() = %q, want %q", got, test.want)
+			}
+		})
 	}
 }