incorrect arguments by default with this

[a-x-]

𝓭𝓮𝓬𝓪𝓯𝓯𝓮𝓲𝓷𝓪𝓽𝓮 is incorrectly transpiling my CoffeeScript input:

source

class Component extends React.PureComponent
  state: {intent: null, yearMonth: null}
  loadData: ({ intent = @state.intent, yearMonth = @state.yearMonth } = {}) =>
    @loadable.request =>
      Api.get '/admin/document_checks/stat_data', { yearMonth, intent }
        .then ({ stats, teams, operators }) => @setState { stats, teams, operators }

REPL

incorrect result (indentation issue is there too):

class Component extends React.PureComponent {
  // ...
  loadData({ intent = intent1, yearMonth = yearMonth1 } = {}) { // 😛 UNDEF
    this.state = state; // 😛 
    this.intent = intent1; // 😛
    this.state = state1; // 😛
    this.yearMonth = yearMonth1; // 😛
    return this.loadable.request(() => {
      return Api.get('/admin/document_checks/stat_data', { yearMonth, intent })
        .then(({ stats, teams, operators }) => this.setState({ stats, teams, operators }));
  });
  }

expected:

class Component extends React.PureComponent {
  // ...
  loadData({ intent = this.state.intent, yearMonth = this.state.yearMonth } = {}) {
    return this.loadable.request(() => {
      return Api.get('/admin/document_checks/stat_data', { yearMonth, intent })
        .then(({ stats, teams, operators }) => this.setState({ stats, teams, operators }));
    });
  }

[a-x-]

It works good w/o the curly braces

loadData: (intent = @state.intent, yearMonth = @state.yearMonth) =>

REPL

[a-x-]

Idea to workaround:

1. grab one or more {...} with @ from function's braces
2. put uniq special argument instead (_tmp_curly_args_hack_1)
3. put {...} = _tmp_curly_args_hack_1 in the first line of body
4. perform all the processing
5. perform procession on {...}
6. move processed {...} back and remove _tmp_curly_args_hack_1

[a-x-]

Another bad cases:
repl

class Component
  foo: (a,{b=@b}, c) ->
    42

class Component {
  foo(a,{b=b1}, c) {
    this.b = b1;
    return 42;
  }
}

[eventualbuddha]

This definitely appears to be a bug. Here's a minimal reproduction:

({ a = @a }) ->

(function({ a = a1 }) {
  this.a = a1;
});

I think the problem is that it's inspecting the whole subtree of nodes for default values to assign, when it shouldn't be doing so with the right hand side of the assignment. I don't know that's the case, but that's what it feels like. I'd be happy to review a PR to fix this.

[a-x-]

has you any beginner's contributor guide?
what tools use, docs read. how conceptually decaffeinate works and etc.

[a-x-]

I tried to patch it and crashed into partially broken TS source maps in the node --inspector and long manual rebuilding (what about adding wath build? I tried, it's not so easy)

[eventualbuddha]

Have you looked at this? https://github.com/decaffeinate/decaffeinate/blob/master/docs/contribution-guide.md

[eventualbuddha]

I was able to fix this case, sort of, by using this:

diff --git a/src/stages/normalize/patchers/MemberAccessOpPatcher.ts b/src/stages/normalize/patchers/MemberAccessOpPatcher.ts
index ea944d0d..f1dccf3c 100644
--- a/src/stages/normalize/patchers/MemberAccessOpPatcher.ts
+++ b/src/stages/normalize/patchers/MemberAccessOpPatcher.ts
@@ -4,6 +4,7 @@ import PassthroughPatcher from '../../../patchers/PassthroughPatcher';
 import { PatcherContext } from '../../../patchers/types';
 import DefaultParamPatcher from './DefaultParamPatcher';
 import IdentifierPatcher from './IdentifierPatcher';
+import AssignOpPatcher from './AssignOpPatcher';
 
 export default class MemberAccessOpPatcher extends PassthroughPatcher {
   node: MemberAccessOp;
@@ -41,6 +42,9 @@ export default class MemberAccessOpPatcher extends PassthroughPatcher {
       if (patcher.parent instanceof DefaultParamPatcher && patcher.parent.value === patcher) {
         break;
       }
+      if (patcher.parent instanceof AssignOpPatcher && patcher.parent.expression === patcher) {
+        break;
+      }
       patcher = patcher.parent;
     }
     return null;

However, that breaks some other cases. We want both of these to work, but I'm not sure how to make that happen:

  it('handles destructured param with `this` member access default value (#1360)', () =>
    checkCS2(
      `
      ({ a = @a }) ->
    `,
      `
      (function({ a = this.a }) {});
    `
    ));

  it('handles destructured param with default value (#1360)', () =>
    checkCS2(
      `
      ({ a } = {}) ->`,
      `
      (function({ a } = {}) {});
      `
    ));