60 lines
1.6 KiB
TypeScript
60 lines
1.6 KiB
TypeScript
import { types as t } from "@babel/core";
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// tries to optimize sequence expressions in the format
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// (a = b, (c => c + e)(a))
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// to
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// (a = b, a + e)
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const buildOptimizedSequenceExpression = ({ call, path, placeholder }) => {
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const { callee: calledExpression } = call;
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const pipelineLeft = path.node.left;
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const assign = t.assignmentExpression(
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"=",
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t.cloneNode(placeholder),
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pipelineLeft,
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);
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let optimizeArrow =
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t.isArrowFunctionExpression(calledExpression) &&
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t.isExpression(calledExpression.body) &&
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!calledExpression.async &&
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!calledExpression.generator;
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let param;
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if (optimizeArrow) {
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const { params } = calledExpression;
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if (params.length === 1 && t.isIdentifier(params[0])) {
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param = params[0];
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} else if (params.length > 0) {
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optimizeArrow = false;
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}
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} else if (t.isIdentifier(calledExpression, { name: "eval" })) {
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const evalSequence = t.sequenceExpression([
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t.numericLiteral(0),
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calledExpression,
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]);
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call.callee = evalSequence;
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path.scope.push({ id: t.cloneNode(placeholder) });
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return t.sequenceExpression([assign, call]);
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}
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if (optimizeArrow && !param) {
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// Arrow function with 0 arguments
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return t.sequenceExpression([pipelineLeft, calledExpression.body]);
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}
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path.scope.push({ id: t.cloneNode(placeholder) });
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if (param) {
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path.get("right").scope.rename(param.name, placeholder.name);
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return t.sequenceExpression([assign, calledExpression.body]);
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}
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return t.sequenceExpression([assign, call]);
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};
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export default buildOptimizedSequenceExpression;
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