func buildFn()

in cmd/php/composer_install/main.go [61:124]
52 lines of code
12 McCabe index (conditional complexity)

func buildFn(ctx *gcp.Context) error {
	if ver, present := os.LookupEnv(php.ComposerVersion); present {
		composerVer = ver
	}

	l, err := ctx.Layer(composerLayer, gcp.BuildLayer, gcp.CacheLayer)
	if err != nil {
		return fmt.Errorf("creating %v layer: %w", composerLayer, err)
	}

	// Check the metadata in the cache layer to determine if we need to proceed.
	metaVersion := ctx.GetMetadata(l, versionKey)
	if composerVer == metaVersion {
		ctx.CacheHit(composerLayer)
		ctx.Logf("composer binary cache hit, skipping installation.")
		return nil
	}
	ctx.CacheMiss(composerLayer)
	if err := ctx.ClearLayer(l); err != nil {
		return fmt.Errorf("clearing layer %q: %w", l.Name, err)
	}

	// download the installer
	installer, err := os.CreateTemp(l.Path, fmt.Sprintf("%s-*.php", composerSetup))
	if err != nil {
		return fmt.Errorf("creating temp file: %w", err)
	}
	defer os.Remove(installer.Name())

	if err := fetch.GetURL(composerSetupURL, installer); err != nil {
		return fmt.Errorf("failed to download composer installer from %s: %w", composerSetupURL, err)
	}

	// verify the installer hash
	var expectedSHABuf bytes.Buffer
	if err := fetch.GetURL(composerSigURL, io.Writer(&expectedSHABuf)); err != nil {
		return fmt.Errorf("failed to fetch the installer signature from %s: %w", composerSigURL, err)
	}
	expectedSHA := expectedSHABuf.String()
	// Disable display_errors to avoid printing warnings to the console when adding the php.ini.
	actualSHACmd := fmt.Sprintf("php -d 'display_errors = Off' -r \"echo hash_file('sha384', '%s');\"", installer.Name())
	result, err := ctx.Exec([]string{"bash", "-c", actualSHACmd})
	if err != nil {
		return err
	}
	actualSHA := result.Stdout
	if actualSHA != expectedSHA {
		return fmt.Errorf("invalid composer installer found at %q: checksum for composer installer, %q, does not match expected checksum of %q", composerSetupURL, actualSHA, expectedSHA)
	}

	// run the installer
	ctx.Logf("installing Composer v%s", composerVer)
	clBin := filepath.Join(l.Path, "bin")
	if err := ctx.MkdirAll(clBin, 0755); err != nil {
		return fmt.Errorf("creating bin folder: %w", err)
	}
	installCmd := fmt.Sprintf("php %s --install-dir %s --filename composer --version %s", installer.Name(), clBin, composerVer)
	if _, err := ctx.Exec([]string{"bash", "-c", installCmd}); err != nil {
		return err
	}

	ctx.SetMetadata(l, versionKey, composerVer)
	return nil
}