fix: set output path based on currently generated output path (#3184)

The output path should be where the code gets generated. This doesn't
match a specific pattern, so for the sake of migration easiest to set it
to the existing output path.

See https://paste.googleplex.com/6379904404946944

Fixes #3130

---------

Signed-off-by: ldetmer <[email protected]>

Author: ldetmer

devtools/cmd/migrate-sidekick/main.go

@@ -40,10 +40,11 @@ const (
 )
 
 var (
-	errRepoNotFound     = errors.New("repo path argument is required")
-	errSidekickNotFound = errors.New(".sidekick.toml not found")
-	errSrcNotFound      = errors.New("src/generated directory not found")
-	errTidyFailed       = errors.New("librarian tidy failed")
+	errRepoNotFound                = errors.New("-repo flag is required")
+	errSidekickNotFound            = errors.New(".sidekick.toml not found")
+	errSrcNotFound                 = errors.New("src/generated directory not found")
+	errTidyFailed                  = errors.New("librarian tidy failed")
+	errUnableToCalculateOutputPath = errors.New("unable to calculate output path")
 )
 
 // SidekickConfig represents the structure of a .sidekick.toml file.
@@ -96,7 +97,6 @@ func run(args []string) error {
 
 	slog.Info("Reading sidekick.toml...", "path", repoPath)
 
-	// Read root .sidekick.toml for defaults
 	defaults, err := readRootSidekick(repoPath)
 	if err != nil {
 		return fmt.Errorf("failed to read root .sidekick.toml: %w", err)
@@ -109,7 +109,7 @@ func run(args []string) error {
 	}
 
 	// Read all sidekick.toml files
-	libraries, err := readSidekickFiles(sidekickFiles)
+	libraries, err := readSidekickFiles(sidekickFiles, repoPath)
 	if err != nil {
 		return fmt.Errorf("failed to read sidekick.toml files: %w", err)
 	}
@@ -242,7 +242,7 @@ func findSidekickFiles(repoPath string) ([]string, error) {
 }
 
 // readSidekickFiles reads all sidekick.toml files and extracts library information.
-func readSidekickFiles(files []string) (map[string]*config.Library, error) {
+func readSidekickFiles(files []string, repoPath string) (map[string]*config.Library, error) {
 	libraries := make(map[string]*config.Library)
 
 	for _, file := range files {
@@ -296,6 +296,11 @@ func readSidekickFiles(files []string) (map[string]*config.Library, error) {
 			libraries[libraryName] = lib
 		}
 		lib.SpecificationFormat = specificationFormat
+		relativePath, err := filepath.Rel(repoPath, dir)
+		if err != nil {
+			return nil, fmt.Errorf("failed to calculate relative path: %w", errUnableToCalculateOutputPath)
+		}
+		lib.Output = relativePath
 
 		// Add channels
 		lib.Channels = append(lib.Channels, &config.Channel{

devtools/cmd/migrate-sidekick/main_test.go

@@ -141,10 +141,11 @@ func TestFindSidekickFiles(t *testing.T) {
 
 func TestReadSidekickFiles(t *testing.T) {
 	for _, test := range []struct {
-		name    string
-		files   []string
-		want    map[string]*config.Library
-		wantErr error
+		name     string
+		files    []string
+		repoName string
+		want     map[string]*config.Library
+		wantErr  error
 	}{
 		{
 			name: "read_sidekick_files",
@@ -165,6 +166,7 @@ func TestReadSidekickFiles(t *testing.T) {
 					CopyrightYear:       "2025",
 					DescriptionOverride: "Description override",
 					SpecificationFormat: "discovery",
+					Output:              "testdata/read-sidekick-files/success-read/nested",
 					Rust: &config.RustCrate{
 						RustDefault: config.RustDefault{
 							DisabledRustdocWarnings: []string{"bare_urls", "broken_intra_doc_links", "redundant_explicit_links"},
@@ -202,6 +204,7 @@ func TestReadSidekickFiles(t *testing.T) {
 					Version:             "1.2.0",
 					CopyrightYear:       "2025",
 					SpecificationFormat: "openapi",
+					Output:              "testdata/read-sidekick-files/success-read",
 					Rust: &config.RustCrate{
 						RustDefault: config.RustDefault{
 							PackageDependencies: []*config.RustPackageDependency{
@@ -238,6 +241,14 @@ func TestReadSidekickFiles(t *testing.T) {
 				},
 			},
 		},
+		{
+			name: "unable_to_calculate_output_path",
+			files: []string{
+				"testdata/read-sidekick-files/success-read/.sidekick.toml",
+			},
+			repoName: "/invalid/repo/path",
+			wantErr:  errUnableToCalculateOutputPath,
+		},
 		{
 			name: "no_api_path",
 			files: []string{
@@ -254,7 +265,7 @@ func TestReadSidekickFiles(t *testing.T) {
 		},
 	} {
 		t.Run(test.name, func(t *testing.T) {
-			got, err := readSidekickFiles(test.files)
+			got, err := readSidekickFiles(test.files, test.repoName)
 			if test.wantErr != nil {
 				if !errors.Is(err, test.wantErr) {
 					t.Errorf("got error %v, want %v", err, test.wantErr)