141 lines
3.5 KiB
JavaScript
141 lines
3.5 KiB
JavaScript
/* eslint max-len: 0 */
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import getFunctionArity from "babel-helper-get-function-arity";
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import callDelegate from "babel-helper-call-delegate";
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import template from "babel-template";
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import * as t from "babel-types";
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let buildDefaultParam = template(`
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let VARIABLE_NAME =
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ARGUMENTS.length > ARGUMENT_KEY && ARGUMENTS[ARGUMENT_KEY] !== undefined ?
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ARGUMENTS[ARGUMENT_KEY]
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:
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DEFAULT_VALUE;
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`);
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let buildCutOff = template(`
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let $0 = $1[$2];
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`);
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function hasDefaults(node) {
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for (let param of (node.params: Array<Object>)) {
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if (!t.isIdentifier(param)) return true;
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}
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return false;
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}
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function isSafeBinding(scope, node) {
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if (!scope.hasOwnBinding(node.name)) return true;
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const { kind } = scope.getOwnBinding(node.name);
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return kind === "param" || kind === "local";
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}
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let iifeVisitor = {
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ReferencedIdentifier(path, state) {
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const { scope, node } = path;
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if (node.name === "eval" || !isSafeBinding(scope, node)) {
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state.iife = true;
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path.stop();
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}
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},
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Scope(path) {
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// different bindings
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path.skip();
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}
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};
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export let visitor = {
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Function(path) {
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let { node, scope } = path;
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if (!hasDefaults(node)) return;
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// ensure it's a block, useful for arrow functions
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path.ensureBlock();
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let state = {
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iife: false,
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scope: scope
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};
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let body = [];
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//
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let argsIdentifier = t.identifier("arguments");
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argsIdentifier._shadowedFunctionLiteral = path;
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// push a default parameter definition
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function pushDefNode(left, right, i) {
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const defNode = buildDefaultParam({
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VARIABLE_NAME: left,
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DEFAULT_VALUE: right,
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ARGUMENT_KEY: t.numericLiteral(i),
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ARGUMENTS: argsIdentifier
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});
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defNode._blockHoist = node.params.length - i;
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body.push(defNode);
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}
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//
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let lastNonDefaultParam = getFunctionArity(node);
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//
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let params = path.get("params");
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for (let i = 0; i < params.length; i++) {
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let param = params[i];
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if (!param.isAssignmentPattern()) {
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if (!state.iife && !param.isIdentifier()) {
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param.traverse(iifeVisitor, state);
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}
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continue;
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}
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let left = param.get("left");
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let right = param.get("right");
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//
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if (i >= lastNonDefaultParam || left.isPattern()) {
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let placeholder = scope.generateUidIdentifier("x");
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placeholder._isDefaultPlaceholder = true;
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node.params[i] = placeholder;
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} else {
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node.params[i] = left.node;
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}
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//
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if (!state.iife) {
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if (right.isIdentifier() && !isSafeBinding(scope, right.node)) {
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// the right hand side references a parameter
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state.iife = true;
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} else {
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right.traverse(iifeVisitor, state);
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}
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}
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pushDefNode(left.node, right.node, i);
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}
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// add declarations for trailing parameters
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for (let i = lastNonDefaultParam + 1; i < node.params.length; i++) {
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let param = node.params[i];
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if (param._isDefaultPlaceholder) continue;
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let declar = buildCutOff(param, argsIdentifier, t.numericLiteral(i));
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declar._blockHoist = node.params.length - i;
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body.push(declar);
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}
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// we need to cut off all trailing parameters
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node.params = node.params.slice(0, lastNonDefaultParam);
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if (state.iife) {
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body.push(callDelegate(path, scope));
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path.set("body", t.blockStatement(body));
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} else {
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path.get("body").unshiftContainer("body", body);
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}
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}
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};
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