createTempVariable() should also try to not shadowing upper lexical environment temp variables

[Jack-Works]

TypeScript Version: 3.9.3

Search Terms:

Code

I'm using createTempVariable but I found it is buggy.

The buggy version: Jack-Works/react@792a7f7#diff-6624517c3255932b3079f651161b7df0

Fixed version:

Jack-Works/react@4ae646b#diff-6624517c3255932b3079f651161b7df0

Reproduction:

const ts = require('typescript')
const t = require('./ReactFreshTypeScriptTransformer.js')

console.log(
 ts.transpileModule(
 `
import { useDefaultWallet } from '../../plugins/Wallet/hooks/useWallet'

/**
 * Get the address of the default wallet
 */
export function useAccount() {
 const wallet = useDefaultWallet()
 return wallet?.address ?? ''
}
`,
 {
 transformers: { before: [t()] },
 compilerOptions: { target: ts.ScriptTarget.ES2017 },
 }
 ).outputText
)

The buggy result using createTempVariable():

var _a;
_a = $RefreshSig$();
import { useDefaultWallet } from '../../plugins/Wallet/hooks/useWallet';
/**
 * Get the address of the default wallet
 */
export function useAccount() {
 var _a;
 _a();
 const wallet = useDefaultWallet();
 return (_a = wallet === null || wallet === void 0 ? void 0 : wallet.address) !== null && _a !== void 0 ? _a : ''; 
}
_a(useAccount, "Zqcse9ORXvHAGVGDGSjWLnVdvA4=", false, () => [useDefaultWallet]);

As you can see, downleveling ?? syntax create a new variable also called "_a" which shadows my upper variable "_a", then _a() leads to an runtime error.

The correct version using createFileLevelUniqueName():

var $c0;
$c0 = $RefreshSig$();
import { useDefaultWallet } from '../../plugins/Wallet/hooks/useWallet';
/**
 * Get the address of the default wallet
 */
export function useAccount() {
 var _a;
 $c0();
 const wallet = useDefaultWallet();
 return (_a = wallet === null || wallet === void 0 ? void 0 : wallet.address) !== null && _a !== void 0 ? _a : '';
}
$c0(useAccount, "Zqcse9ORXvHAGVGDGSjWLnVdvA4=", false, () => [useDefaultWallet]);

[Jack-Works]

If createTempVariable can accept this enum, this problem will be resolved!

export enum GeneratedIdentifierFlags {
 None = 0,
 ReservedInNestedScopes = 8,
 Optimistic = 16,
 FileLevel = 32,
 AllowNameSubstitution = 64
 }

[Jack-Works]

Exposed: (4.1.0 beta) signature

createTempVariable(recordTempVariable: ((node: Identifier) => void) | undefined): Identifier

Signature in source code:

createTempVariable(recordTempVariable: ((node: Identifier) => void) | undefined, reservedInNestedScopes?: boolean): GeneratedIdentifier

[Jack-Works]

Please explosure those signatures! It's very useful when transforming code

[rbuckton]

In the meantime, is factory.createUniqueName an option?

[Jack-Works]

In the meantime, is factory.createUniqueName an option?

I don't know, but expose reservedInNestedScopes?: boolean will be very useful