101 lines
2.7 KiB
JavaScript
101 lines
2.7 KiB
JavaScript
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"use strict";
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// Simple AST node visitor builder.
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const visitor = {
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build(functions) {
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function visit(node, ...args) {
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return functions[node.type](node, ...args);
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}
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function visitNop() {
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// Do nothing.
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}
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function visitExpression(node, ...args) {
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return visit(node.expression, ...args);
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}
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function visitChildren(property) {
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return function(node, ...args) {
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// We do not use .map() here, because if you need the result
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// of applying visitor to children you probable also need to
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// process it in some way, therefore you anyway have to override
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// this method. If you do not needed that, we do not waste time
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// and memory for creating the output array
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node[property].forEach(child => visit(child, ...args));
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};
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}
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const DEFAULT_FUNCTIONS = {
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grammar(node, ...args) {
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for (const imp of node.imports) {
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visit(imp, ...args);
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}
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if (node.topLevelInitializer) {
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if (Array.isArray(node.topLevelInitializer)) {
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for (const tli of node.topLevelInitializer) {
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visit(tli, ...args);
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}
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} else {
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visit(node.topLevelInitializer, ...args);
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}
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}
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if (node.initializer) {
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if (Array.isArray(node.initializer)) {
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for (const init of node.initializer) {
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visit(init, ...args);
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}
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} else {
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visit(node.initializer, ...args);
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}
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}
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node.rules.forEach(rule => visit(rule, ...args));
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},
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grammar_import: visitNop,
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top_level_initializer: visitNop,
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initializer: visitNop,
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rule: visitExpression,
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named: visitExpression,
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choice: visitChildren("alternatives"),
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action: visitExpression,
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sequence: visitChildren("elements"),
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labeled: visitExpression,
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text: visitExpression,
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simple_and: visitExpression,
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simple_not: visitExpression,
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optional: visitExpression,
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zero_or_more: visitExpression,
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one_or_more: visitExpression,
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repeated(node, ...args) {
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if (node.delimiter) {
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visit(node.delimiter, ...args);
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}
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return visit(node.expression, ...args);
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},
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group: visitExpression,
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semantic_and: visitNop,
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semantic_not: visitNop,
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rule_ref: visitNop,
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library_ref: visitNop,
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literal: visitNop,
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class: visitNop,
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any: visitNop,
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};
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Object.keys(DEFAULT_FUNCTIONS).forEach(type => {
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if (!Object.prototype.hasOwnProperty.call(functions, type)) {
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functions[type] = DEFAULT_FUNCTIONS[type];
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}
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});
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return visit;
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},
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};
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module.exports = visitor;
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