const in ambient context incorrectly flagged as uninitialised

[sverweij]

Describe the bug

Since #3742 was introduced in version 1.2.46 (issue: #3730), not only uninitialised. const declarations in 'strict' mode/ real code get flagged with error: 'const' declarations must be initialized but also those in ambient context (type declaration only/ .d.ts). However in ambient contexts a const cannot be initialised; tsc will complain with a TS1039: Initializers are not allowed in ambient contexts.ts(1039)

Input code

// filename: types.d.ts
export const aThing: IAnInterface[];

export interface IAnInterface {
  anAttribute: string;
  anotherAttribute: boolean;
}

Config

{
  "jsc": {
    "parser": {
      "syntax": "typescript",
      "tsx": false,
      "decorators": true
    },
    "target": "es2022",
    "loose": false,
    "minify": {
      "compress": false,
      "mangle": false
    }
  },
  "module": {
    "type": "es6",
    "strict": false,
    "strictMode": false
  },
  "minify": false,
  "isModule": true
}

Playground link

https://play.swc.rs/?version=1.2.149&code=H4sIAAAAAAAAA1WMMQqEMBBF%2BznFnEB7U1nab7dYRHeigTAjyRd2Wby7Igjafd5%2FvLrmEJM0jN8ipfpUKCTfxTJ4NC1g%2F5qjTg13rXYKycGP8u4dXVa84MPgPzF7bYEchxVHvxxLJ3diwyz59g1mSbw62mgHJbEkGZAAAAA%3D&config=H4sIAAAAAAAAA0WOSw6DMAwF7%2BI1iyqLLrgDh4iCQakAR35GKoq4e0OgsPNvxi%2FTB4HaTMkrWI8K22L%2BSy3ZlhhBYzJqyFBGg5%2FADfUcRL2JglrTlfey9jqyFYjhXs4VYBIB38gclzhshz7InJSBZ%2BWXcfpf7sU1S78eg1wTVOe7CGEag93Y2XbS3%2Bjz5TqJ6C5VTfkDjgOVHewAAAA%3D

Expected behavior

In ambient contexts (type declaration files) uninitialised const declarations are allowed.

Actual behavior

error: 'const' declarations must be initialized

Version

@swc/core 1.2.149

Additional context

• I've tried to play around with parser options (e.g. to indicate the input is not strict) but failed to do so. If there's an option to influence this behavior, I'll be all ears.
• I encountered this issue while using @swc/core for static analysis (and not with the swc cli per se). Sample snippet:

const SWC_PARSE_OPTIONS = {
  dynamicImport: true,
  syntax: "typescript",
  target: "es2022",
};
console.dir(
  swc.parseFileSync('types.d.ts', SWC_PARSE_OPTIONS), 
  {depth:10}
)

// no output, but instead on stderr:
/* 
Uncaught Error: error: 'const' declarations must be initialized
  --> types.d.ts:2:14
   |
14 | export const aThing: IAnInterface[];
   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^



Caused by:
    0: error was recoverable, but proceeding would result in wrong codegen
    1: Syntax Error
    at Compiler.parseFileSync (/Users/sander/thing/node_modules/@swc/core/index.js:87:36)
    at Object.parseFileSync (/Users/sander/thing/node_modules/@swc/core/index.js:201:21) {
  code: 'GenericFailure'
*/

[kdy1]

I'll fix this right away and publish a new verison.

[sverweij]

That was very quick!! Thanks @kdy1 👍

[sverweij]

@kdy1 I've retested with v1.2.150 - but it seems the issue remains - at least when run against swc.parseFile or swc.parseFileSync with the code from Additional context in the description above:

// file: types.d.ts
export const aThing: IAnInterface[];

export interface IAnInterface {
  anAttribute: string;
  anotherAttribute: boolean;
}

// file: test_swc.js
const swc = require('@swc/core')

console.log(`swc version: ${swc.version}`)

const SWC_PARSE_OPTIONS = {
  dynamicImport: true,
  syntax: "typescript",
  target: "es2022",
};

console.dir(
  swc.parseFileSync('types.d.ts', SWC_PARSE_OPTIONS), 
  {depth:10}
)

$ node test_swc.js
swc version: 1.2.150
/Users/sander/thing/node_modules/@swc/core/index.js:87
        return JSON.parse(bindings.parseFileSync(path, toBuffer(options)));
                                   ^

Error: error: 'const' declarations must be initialized
 --> types.d.ts:1:14
  |
1 | export const aThing: IAnInterface[];
  |              ^^^^^^^^^^^^^^^^^^^^^^



Caused by:
    0: error was recoverable, but proceeding would result in wrong codegen
    1: Syntax Error
    at Compiler.parseFileSync (/Users/sander/thing/node_modules/@swc/core/index.js:87:36)
    at Object.parseFileSync (/Users/sander/thing/node_modules/@swc/core/index.js:201:21)
    at Object.<anonymous> (/Users/sander/thing/test_swc.js:13:7)
    at Module._compile (node:internal/modules/cjs/loader:1097:14)
    at Object.Module._extensions..js (node:internal/modules/cjs/loader:1149:10)
    at Module.load (node:internal/modules/cjs/loader:975:32)
    at Function.Module._load (node:internal/modules/cjs/loader:822:12)
    at Function.executeUserEntryPoint [as runMain] (node:internal/modules/run_main:77:12)
    at node:internal/main/run_main_module:17:47 {
  code: 'GenericFailure'
}

Node.js v17.4.0

[kdy1]

For parseFile it's matter of option

[sverweij]

Hi @kdy1 that's what I expected as well. However, I've been looking for an option that'd work here, but weren't able to.

parseFile (/ parseFileSync/ parse/ parseSync) takes a 2nd parameter of the type ParseOptions which is defined in node-swc/rc/types.ts, but it doesn't seem to have something to e.g. influence whether to interpret typescript strictly (as targeted in PR #3742) or ambiently f.t.m.; summarised, for modules of "typescript" syntax, these are the options I see:

{
  syntax: "typescript";
  /**
   * Defaults to `false`.
   */
  tsx?: boolean;
  /**
   * Defaults to `false`.
   */
  decorators?: boolean;
  /**
   * Defaults to `false`
   */
  dynamicImport?: boolean;
  comments?: boolean;
  script?: boolean;
  /**
   * Defaults to es3.
   */
  target?: JscTarget;
}

Is it possible to pass more/ different things to the parse* functions than documented in that type?

There are strict and strictMode options in the module part of an swc config, but if I understand correctly that's for influencing what swc emits only.

[kdy1]

It has a hidden field.
Btw, you are not expected to process d.ts file using swc

[swc-bot]

This closed issue has been automatically locked because it had no new activity for a month. If you are running into a similar issue, please create a new issue with the steps to reproduce. Thank you.