Function parseHostBindings

packages/compiler/src/render3/view/compiler.ts:519–572

(host: {
  [key: string]: string | o.Expression;
})

}

export function parseHostBindings(host: {
  [key: string]: string | o.Expression;
}): ParsedHostBindings {
  const attributes: Record<string, o.Expression> = {};
  const listeners: Record<string, string> = {};
  const properties: Record<string, string> = {};
  const specialAttributes: {styleAttr?: string; classAttr?: string} = {};

  for (const key of Object.keys(host)) {
    const value = host[key];

    if (key.startsWith('(') && key.endsWith(')')) {
      if (typeof value !== 'string') {
        // TODO(alxhub): make this a diagnostic.
        throw new Error(`Event binding must be string`);
      }
      listeners[key.slice(1, -1)] = value;
    } else if (key.startsWith('[') && key.endsWith(']')) {
      if (typeof value !== 'string') {
        // TODO(alxhub): make this a diagnostic.
        throw new Error(`Property binding must be string`);
      }
      // synthetic properties (the ones that have a `@` as a prefix)
      // are still treated the same as regular properties. Therefore
      // there is no point in storing them in a separate map.
      properties[key.slice(1, -1)] = value;
    } else {
      switch (key) {
        case 'class':
          if (typeof value !== 'string') {
            // TODO(alxhub): make this a diagnostic.
            throw new Error(`Class binding must be string`);
          }
          specialAttributes.classAttr = value;
          break;
        case 'style':
          if (typeof value !== 'string') {
            // TODO(alxhub): make this a diagnostic.
            throw new Error(`Style binding must be string`);
          }
          specialAttributes.styleAttr = value;
          break;
        default:
          if (typeof value === 'string') {
            attributes[key] = o.literal(value);
          } else {
            attributes[key] = value;
          }
      }
    }
  }

  return {attributes, listeners, properties, specialAttributes};
}

/**
 * Verifies host bindings and returns the list of errors (if any). Empty array indicates that a