Configuration

You can configure cem via a cem.yaml file in your project’s .config directory, or by using command-line flags.

Configuration File

Here is a complete example of a .config/cem.yaml file with all available options explained.

# The canonical public source control URL for your repository root.
# Used for generating source links in the manifest.
sourceControlRootUrl: "https://github.com/your/repo/tree/main/"

# Configuration for the `generate` command.
generate:
  # A list of glob patterns for files to include in the analysis.
  files:
    - "src/**/*.ts"

  # A list of glob patterns for files to exclude from the analysis.
  exclude:
    - "src/**/*.test.ts"

  # The path to write the final custom-elements.json manifest.
  # If omitted, the manifest is written to standard output.
  output: "custom-elements.json"

  # By default, certain files like TypeScript declaration files (`.d.ts`) are excluded.
  # Set to `true` to include all files matched by the `files` glob.
  noDefaultExcludes: false

  # Configuration for integrating Design Tokens.
  designTokens:
    # An npm specifier or local path to a DTCG-formatted JSON module.
    spec: "npm:@my-ds/tokens/tokens.json"
    # A CSS custom property prefix to apply to the design tokens.
    prefix: "--my-ds"

  # Configuration for discovering element demos.
  demoDiscovery:
    # A glob pattern to find demo files.
    fileGlob: "demos/**/*.html"
    # A Go regexp with named capture groups to extract information from demo file paths.
    urlPattern: "demos/(?P<tag>[\\w-]+)/(?P<demo>[\\w-]+).html"
    # A template to construct the canonical URL for a demo.
    # Uses `{groupName}` syntax to interpolate captures from `urlPattern`.
    urlTemplate: "https://example.com/elements/{tag}/{demo}/"

Global Flags

These flags can be used with any cem command.

Flag	Description
`--config`	Path to a custom config file.
`--package`	deno-style package specifier, or path to the local package directory.
`--verbose`, -v	Enable verbose logging output.
`--help`, -h	Show help for a command.

Command-Line Flags

All configuration options can also be set via command-line flags. Flags will always override any values set in the configuration file.

For example, to override the output and exclude options for the generate command:

cem generate --output my-manifest.json --exclude "src/legacy/**"