99be60b53d
* Implement transform for nullish-coalescing operator * Update example output * Switch from BinaryExpression to LogicalExpression * Address review comments - Use generateUidIdentifierBasedOnNode - Inline "??" - Clone ref node - Move "??" to LogicalExpression in babel-types * Fix reference to @babel/helper-plugin-test-runner * Fix reference to @babel/plugin-syntax-nullish-coalescing-operator * Don't use parent scope * Remove .vscode from .gitignore, change 'lib/index.js' to 'lib' * Ensure `document.all ?? 0 === document.all` * Fix note and copy to an inline comment
41 lines
1.1 KiB
JavaScript
41 lines
1.1 KiB
JavaScript
import syntaxNullishCoalescingOperator from "@babel/plugin-syntax-nullish-coalescing-operator";
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export default function({ types: t }) {
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return {
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inherits: syntaxNullishCoalescingOperator,
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visitor: {
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LogicalExpression(path) {
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const { node, scope } = path;
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if (node.operator !== "??") {
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return;
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}
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const ref = scope.generateUidIdentifierBasedOnNode(node.left);
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scope.push({ id: ref });
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path.replaceWith(
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t.sequenceExpression([
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t.assignmentExpression("=", ref, node.left),
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t.conditionalExpression(
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// We cannot use `!= null` here because `document.all == null`
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// and `document.all` has been deemed not "nullish".
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t.logicalExpression(
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"&&",
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t.binaryExpression("!==", t.clone(ref), t.nullLiteral()),
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t.binaryExpression(
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"!==",
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t.clone(ref),
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scope.buildUndefinedNode(),
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),
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),
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t.clone(ref),
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node.right,
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),
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]),
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);
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},
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},
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};
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}
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