devsite/node_modules/sucrase/dist/esm/identifyShadowedGlobals.js
2024-07-07 18:49:38 -07:00

99 lines
2.9 KiB
JavaScript

import {
isBlockScopedDeclaration,
isFunctionScopedDeclaration,
isNonTopLevelDeclaration,
} from "./parser/tokenizer";
import {TokenType as tt} from "./parser/tokenizer/types";
/**
* Traverse the given tokens and modify them if necessary to indicate that some names shadow global
* variables.
*/
export default function identifyShadowedGlobals(
tokens,
scopes,
globalNames,
) {
if (!hasShadowedGlobals(tokens, globalNames)) {
return;
}
markShadowedGlobals(tokens, scopes, globalNames);
}
/**
* We can do a fast up-front check to see if there are any declarations to global names. If not,
* then there's no point in computing scope assignments.
*/
// Exported for testing.
export function hasShadowedGlobals(tokens, globalNames) {
for (const token of tokens.tokens) {
if (
token.type === tt.name &&
!token.isType &&
isNonTopLevelDeclaration(token) &&
globalNames.has(tokens.identifierNameForToken(token))
) {
return true;
}
}
return false;
}
function markShadowedGlobals(
tokens,
scopes,
globalNames,
) {
const scopeStack = [];
let scopeIndex = scopes.length - 1;
// Scopes were generated at completion time, so they're sorted by end index, so we can maintain a
// good stack by going backwards through them.
for (let i = tokens.tokens.length - 1; ; i--) {
while (scopeStack.length > 0 && scopeStack[scopeStack.length - 1].startTokenIndex === i + 1) {
scopeStack.pop();
}
while (scopeIndex >= 0 && scopes[scopeIndex].endTokenIndex === i + 1) {
scopeStack.push(scopes[scopeIndex]);
scopeIndex--;
}
// Process scopes after the last iteration so we can make sure we pop all of them.
if (i < 0) {
break;
}
const token = tokens.tokens[i];
const name = tokens.identifierNameForToken(token);
if (scopeStack.length > 1 && !token.isType && token.type === tt.name && globalNames.has(name)) {
if (isBlockScopedDeclaration(token)) {
markShadowedForScope(scopeStack[scopeStack.length - 1], tokens, name);
} else if (isFunctionScopedDeclaration(token)) {
let stackIndex = scopeStack.length - 1;
while (stackIndex > 0 && !scopeStack[stackIndex].isFunctionScope) {
stackIndex--;
}
if (stackIndex < 0) {
throw new Error("Did not find parent function scope.");
}
markShadowedForScope(scopeStack[stackIndex], tokens, name);
}
}
}
if (scopeStack.length > 0) {
throw new Error("Expected empty scope stack after processing file.");
}
}
function markShadowedForScope(scope, tokens, name) {
for (let i = scope.startTokenIndex; i < scope.endTokenIndex; i++) {
const token = tokens.tokens[i];
if (
(token.type === tt.name || token.type === tt.jsxName) &&
tokens.identifierNameForToken(token) === name
) {
token.shadowsGlobal = true;
}
}
}