Function isStructurallySame

packages/icu-messageformat-parser/manipulator.ts:217–259

(
  a: MessageFormatElement[],
  b: MessageFormatElement[]
)

 * @returns
 */
export function isStructurallySame(
  a: MessageFormatElement[],
  b: MessageFormatElement[]
): IsStructurallySameResult {
  const aVars = new Map<string, TYPE>()
  const bVars = new Map<string, TYPE>()
  collectVariables(a, aVars)
  collectVariables(b, bVars)

  if (aVars.size !== bVars.size) {
    return {
      success: false,
      error: new Error(
        `Different number of variables: [${Array.from(aVars.keys()).join(', ')}] vs [${Array.from(bVars.keys()).join(', ')}]`
      ),
    }
  }

  return Array.from(aVars.entries()).reduce<IsStructurallySameResult>(
    (result, [key, type]) => {
      if (!result.success) {
        return result
      }
      const bType = bVars.get(key)
      if (bType == null) {
        return {
          success: false,
          error: new Error(`Missing variable ${key} in message`),
        }
      }
      if (bType !== type) {
        return {
          success: false,
          error: new Error(
            `Variable ${key} has conflicting types: ${TYPE[type]} vs ${TYPE[bType]}`
          ),
        }
      }
      return result
    },
    {success: true}
  )
}