func buildFn()

in cmd/java/maven/main.go [65:130]
50 lines of code
16 McCabe index (conditional complexity)

func buildFn(ctx *gcp.Context) error {
	m2CachedRepo, err := ctx.Layer(m2Layer, gcp.CacheLayer, gcp.LaunchLayerIfDevMode)
	if err != nil {
		return fmt.Errorf("creating %v layer: %w", m2Layer, err)
	}
	if err := java.CheckCacheExpiration(ctx, m2CachedRepo); err != nil {
		return fmt.Errorf("validating the cache: %w", err)
	}

	homeM2 := filepath.Join(ctx.HomeDir(), ".m2")
	// Symlink the m2 layer into ~/.m2. If ~/.m2 already exists, delete it first.
	// If it exists as a symlink, RemoveAll will remove the link, not anything it's linked to.
	// We can't just use `-Dmaven.repo.local`. It does set the path to `m2/repo` but it fails
	// to set the path to `m2/wrapper` which is used by mvnw to download Maven.
	if err := ctx.RemoveAll(homeM2); err != nil {
		return err
	}
	if err := ctx.Symlink(m2CachedRepo.Path, homeM2); err != nil {
		return err
	}

	if err := addJvmConfig(ctx); err != nil {
		return err
	}

	mvn, err := provisionOrDetectMaven(ctx)
	if err != nil {
		return err
	}

	command := []string{mvn, "clean", "package", "--batch-mode", "-DskipTests", "-Dhttp.keepAlive=false"}

	pomPath, err := pomFilePath(ctx)
	if err != nil {
		return err
	}
	if pomPath != "" {
		command = append(command, fmt.Sprintf("-f=%s", pomPath))
	}

	if buildArgs := os.Getenv(env.BuildArgs); buildArgs != "" {
		if strings.Contains(buildArgs, "maven.repo.local") {
			ctx.Warnf("Detected maven.repo.local property set in GOOGLE_BUILD_ARGS. Maven caching may not work properly.")
		}
		command = append(command, strings.Fields(buildArgs)...)
	}

	if mvnBuildArgs := os.Getenv(java.MavenBuildArgs); mvnBuildArgs != "" {
		command = append([]string{mvn}, strings.Fields(mvnBuildArgs)...)
	}

	if !ctx.Debug() && !devmode.Enabled(ctx) {
		command = append(command, "--quiet")
	}

	if _, err := ctx.Exec(command, gcp.WithStdoutTail, gcp.WithUserAttribution); err != nil {
		return err
	}

	// Store the build steps in a script to be run on each file change.
	if devmode.Enabled(ctx) {
		devmode.WriteBuildScript(ctx, m2CachedRepo.Path, "~/.m2", command)
	}

	return nil
}