.match issues with TypeScript and fromCapture

[j4k0xb]

The m.match function doesn't seem to properly work with TypeScript. Example from the jsdoc:

import * as m from '@codemod/matchers';

let id: m.CapturedMatcher<t.Identifier>;
const idPlusIdMatcher = m.binaryExpression(
  '+',
  (id = m.capture(m.identifier())),
  m.fromCapture(id)
);

export default function() {
  return {
    BinaryExpression(path: NodePath<t.BinaryExpression>): void {
      m.match(idPlusIdMatcher, { id }, path.node, ({ id }) => {
        path.replaceWith(t.binaryExpression('*', id, t.numericLiteral(2)));
      });
    }
  };
}

This can be fixed by importing from ../matchers instead, because the published package doesn't contain src.

codemod/packages/matchers/src/utils/match.ts

Line 1 in 505da37

import * as m from '../../src/matchers'

codemod/packages/matchers/src/utils/matchPath.ts

Line 1 in 505da37

import * as m from '../../src/matchers'

Another thing I noticed is that .fromCapture only works with captured primitives like strings, not matchers themselves:

// fails
const id = m.capture(m.identifier())
const idPlusIdMatcher = m.binaryExpression('+', id, m.fromCapture(id))

// works
const idValue = m.capture(m.anyString())
const idPlusIdMatcher = m.binaryExpression(
  '+',
  m.identifier(idValue),
  m.identifier(m.fromCapture(idValue))
)

Would be nice if both ways work to compare whole code structures

And when matching with containers it shouldn't narrow the type:

if (idPlusIdMatcher.match(ast)) {
  console.log(path.node) // TS says "t.BinaryExpression", at runtime it's e.g. "t.Program"

[eventualbuddha]

Fixed in v1.3.1.

[eventualbuddha]

And I liked your suggestion for the behavior of fromCapture, so I changed that in v1.4.0.

[eventualbuddha]

And I also have an idea for the type narrowing thing. Stay tuned.