langium
Version:
A language engineering tool for the Language Server Protocol
474 lines • 17.2 kB
JavaScript
/******************************************************************************
* Copyright 2022 TypeFox GmbH
* This program and the accompanying materials are made available under the
* terms of the MIT License, which is available in the project root.
******************************************************************************/
import { EMPTY_ALT, EOF } from 'chevrotain';
import { isAction, isAlternatives, isEndOfFile, isAssignment, isConjunction, isCrossReference, isDisjunction, isGroup, isKeyword, isNegation, isParameterReference, isParserRule, isRuleCall, isTerminalRule, isUnorderedGroup, isBooleanLiteral, isInfixRule, isAbstractParserRule } from '../languages/generated/ast.js';
import { assertUnreachable, ErrorWithLocation } from '../utils/errors.js';
import { stream } from '../utils/stream.js';
import { findNameAssignment, getAllReachableRules, getTypeName } from '../utils/grammar-utils.js';
export function createParser(grammar, parser, tokens) {
const parserContext = {
parser,
tokens,
ruleNames: new Map()
};
buildRules(parserContext, grammar);
return parser;
}
function buildRules(parserContext, grammar) {
const reachable = getAllReachableRules(grammar, false);
const parserRules = stream(grammar.rules).filter(isParserRule).filter(rule => reachable.has(rule));
for (const rule of parserRules) {
const ctx = {
...parserContext,
consume: 1,
optional: 1,
subrule: 1,
many: 1,
or: 1
};
parserContext.parser.rule(rule, buildElement(ctx, rule.definition));
}
const infixRules = stream(grammar.rules).filter(isInfixRule).filter(rule => reachable.has(rule));
for (const rule of infixRules) {
parserContext.parser.rule(rule, buildInfixRule(parserContext, rule));
}
}
function buildInfixRule(ctx, rule) {
const expressionRule = rule.call.rule.ref;
if (!expressionRule) {
throw new Error('Could not resolve reference to infix operator rule: ' + rule.call.rule.$refText);
}
if (isTerminalRule(expressionRule)) {
throw new Error('Cannot use terminal rule in infix expression');
}
// We need to construct a bunch of synthetic grammar AST nodes here
// This ensures that the CST and completion engine get populated as expected
const allKeywords = rule.operators.precedences.flatMap(e => e.operators);
// The outer group represents the first expression call and the whole (optional) loop
const outerGroup = {
$type: 'Group',
elements: []
};
const part1Assignment = {
$container: outerGroup,
$type: 'Assignment',
feature: 'parts',
operator: '+=',
terminal: rule.call
};
// The inner group represents the loop that contains the operator and expression call
// It can be infinitely repeated
const innerGroup = {
$container: outerGroup,
$type: 'Group',
elements: [],
cardinality: '*'
};
outerGroup.elements.push(part1Assignment, innerGroup);
// Store all operator keywords in one alternative/assignment
const alternatives = {
$type: 'Alternatives',
elements: allKeywords
};
const operatorAssignment = {
$container: innerGroup,
$type: 'Assignment',
feature: 'operators',
operator: '+=',
terminal: alternatives
};
// We need a second assignment of the called expression here
const part2Assignment = {
...part1Assignment,
$container: innerGroup
};
innerGroup.elements.push(operatorAssignment, part2Assignment);
const tokens = allKeywords.map(e => ctx.tokens[e.value]);
const orAlts = tokens.map((token, index) => ({
ALT: () => ctx.parser.consume(index, token, operatorAssignment)
}));
let subrule;
return (args) => {
subrule ?? (subrule = getRule(ctx, expressionRule));
ctx.parser.subrule(0, subrule, false, part1Assignment, args);
ctx.parser.many(0, {
DEF: () => {
ctx.parser.alternatives(0, orAlts);
ctx.parser.subrule(1, subrule, false, part2Assignment, args);
}
});
};
}
function buildElement(ctx, element, ignoreGuard = false) {
let method;
if (isKeyword(element)) {
method = buildKeyword(ctx, element);
}
else if (isAction(element)) {
method = buildAction(ctx, element);
}
else if (isAssignment(element)) {
method = buildElement(ctx, element.terminal);
}
else if (isCrossReference(element)) {
method = buildCrossReference(ctx, element);
}
else if (isRuleCall(element)) {
method = buildRuleCall(ctx, element);
}
else if (isAlternatives(element)) {
method = buildAlternatives(ctx, element);
}
else if (isUnorderedGroup(element)) {
method = buildUnorderedGroup(ctx, element);
}
else if (isGroup(element)) {
method = buildGroup(ctx, element);
}
else if (isEndOfFile(element)) {
const idx = ctx.consume++;
method = () => ctx.parser.consume(idx, EOF, element);
}
else {
throw new ErrorWithLocation(element.$cstNode, `Unexpected element type: ${element.$type}`);
}
return wrap(ctx, ignoreGuard ? undefined : getGuardCondition(element), method, element.cardinality);
}
function buildAction(ctx, action) {
const actionType = getTypeName(action);
return () => ctx.parser.action(actionType, action);
}
function buildRuleCall(ctx, ruleCall) {
const rule = ruleCall.rule.ref;
if (isAbstractParserRule(rule)) {
const idx = ctx.subrule++;
const fragment = isParserRule(rule) && rule.fragment;
const predicate = ruleCall.arguments.length > 0 ? buildRuleCallPredicate(rule, ruleCall.arguments) : () => ({});
let subrule;
return (args) => {
subrule ?? (subrule = getRule(ctx, rule));
ctx.parser.subrule(idx, subrule, fragment, ruleCall, predicate(args));
};
}
else if (isTerminalRule(rule)) {
const idx = ctx.consume++;
const method = getToken(ctx, rule.name);
return () => ctx.parser.consume(idx, method, ruleCall);
}
else if (!rule) {
throw new ErrorWithLocation(ruleCall.$cstNode, `Undefined rule: ${ruleCall.rule.$refText}`);
}
else {
assertUnreachable(rule);
}
}
function buildRuleCallPredicate(rule, namedArgs) {
const hasNamedArguments = namedArgs.some(arg => arg.calledByName);
if (hasNamedArguments) {
const namedPredicates = namedArgs.map(arg => ({
parameterName: arg.parameter?.ref?.name,
predicate: buildPredicate(arg.value)
}));
return (args) => {
const ruleArgs = {};
for (const { parameterName, predicate } of namedPredicates) {
if (parameterName) {
ruleArgs[parameterName] = predicate(args);
}
}
return ruleArgs;
};
}
else {
const predicates = namedArgs.map(arg => buildPredicate(arg.value));
return (args) => {
const ruleArgs = {};
for (let i = 0; i < predicates.length; i++) {
if (i < rule.parameters.length) {
const parameterName = rule.parameters[i].name;
const predicate = predicates[i];
ruleArgs[parameterName] = predicate(args);
}
}
return ruleArgs;
};
}
}
function buildPredicate(condition) {
if (isDisjunction(condition)) {
const left = buildPredicate(condition.left);
const right = buildPredicate(condition.right);
return (args) => (left(args) || right(args));
}
else if (isConjunction(condition)) {
const left = buildPredicate(condition.left);
const right = buildPredicate(condition.right);
return (args) => (left(args) && right(args));
}
else if (isNegation(condition)) {
const value = buildPredicate(condition.value);
return (args) => !value(args);
}
else if (isParameterReference(condition)) {
const name = condition.parameter.ref.name;
return (args) => args !== undefined && args[name] === true;
}
else if (isBooleanLiteral(condition)) {
const value = Boolean(condition.true);
return () => value;
}
assertUnreachable(condition);
}
function buildAlternatives(ctx, alternatives) {
if (alternatives.elements.length === 1) {
return buildElement(ctx, alternatives.elements[0]);
}
else {
const methods = [];
for (const element of alternatives.elements) {
const predicatedMethod = {
// Since we handle the guard condition in the alternative already
// We can ignore the group guard condition inside
ALT: buildElement(ctx, element, true)
};
const guard = getGuardCondition(element);
if (guard) {
predicatedMethod.GATE = buildPredicate(guard);
}
methods.push(predicatedMethod);
}
const idx = ctx.or++;
return (args) => ctx.parser.alternatives(idx, methods.map(method => {
const alt = {
ALT: () => method.ALT(args)
};
const gate = method.GATE;
if (gate) {
alt.GATE = () => gate(args);
}
return alt;
}));
}
}
function buildUnorderedGroup(ctx, group) {
if (group.elements.length === 1) {
return buildElement(ctx, group.elements[0]);
}
const methods = [];
for (const element of group.elements) {
const predicatedMethod = {
// Since we handle the guard condition in the alternative already
// We can ignore the group guard condition inside
ALT: buildElement(ctx, element, true)
};
const guard = getGuardCondition(element);
if (guard) {
predicatedMethod.GATE = buildPredicate(guard);
}
methods.push(predicatedMethod);
}
const orIdx = ctx.or++;
const idFunc = (groupIdx, lParser) => {
const stackId = lParser.getRuleStack().join('-');
return `uGroup_${groupIdx}_${stackId}`;
};
const alternatives = (args) => ctx.parser.alternatives(orIdx, methods.map((method, idx) => {
const alt = { ALT: () => true };
const parser = ctx.parser;
alt.ALT = () => {
method.ALT(args);
if (!parser.isRecording()) {
const key = idFunc(orIdx, parser);
if (!parser.unorderedGroups.get(key)) {
// init after clear state
parser.unorderedGroups.set(key, []);
}
const groupState = parser.unorderedGroups.get(key);
if (typeof groupState?.[idx] === 'undefined') {
// Not accessed yet
groupState[idx] = true;
}
}
};
const gate = method.GATE;
if (gate) {
alt.GATE = () => gate(args);
}
else {
alt.GATE = () => {
const trackedAlternatives = parser.unorderedGroups.get(idFunc(orIdx, parser));
const allow = !trackedAlternatives?.[idx];
return allow;
};
}
return alt;
}));
const wrapped = wrap(ctx, getGuardCondition(group), alternatives, '*');
return (args) => {
wrapped(args);
if (!ctx.parser.isRecording()) {
ctx.parser.unorderedGroups.delete(idFunc(orIdx, ctx.parser));
}
};
}
function buildGroup(ctx, group) {
const methods = group.elements.map(e => buildElement(ctx, e));
return (args) => methods.forEach(method => method(args));
}
function getGuardCondition(element) {
if (isGroup(element)) {
return element.guardCondition;
}
return undefined;
}
function buildCrossReference(ctx, crossRef, terminal = crossRef.terminal) {
if (!terminal) {
if (!crossRef.type.ref) {
throw new Error('Could not resolve reference to type: ' + crossRef.type.$refText);
}
const assignment = findNameAssignment(crossRef.type.ref);
const assignTerminal = assignment?.terminal;
if (!assignTerminal) {
throw new Error('Could not find name assignment for type: ' + getTypeName(crossRef.type.ref));
}
return buildCrossReference(ctx, crossRef, assignTerminal);
}
else if (isRuleCall(terminal) && isParserRule(terminal.rule.ref)) {
// The terminal is a data type rule here. Everything else will result in a validation error.
const rule = terminal.rule.ref;
const idx = ctx.subrule++;
let subrule;
return (args) => {
subrule ?? (subrule = getRule(ctx, rule));
ctx.parser.subrule(idx, subrule, false, crossRef, args);
};
}
else if (isRuleCall(terminal) && isTerminalRule(terminal.rule.ref)) {
const idx = ctx.consume++;
const terminalRule = getToken(ctx, terminal.rule.ref.name);
return () => ctx.parser.consume(idx, terminalRule, crossRef);
}
else if (isKeyword(terminal)) {
const idx = ctx.consume++;
const keyword = getToken(ctx, terminal.value);
return () => ctx.parser.consume(idx, keyword, crossRef);
}
else {
throw new Error('Could not build cross reference parser');
}
}
function buildKeyword(ctx, keyword) {
const idx = ctx.consume++;
const token = ctx.tokens[keyword.value];
if (!token) {
throw new Error('Could not find token for keyword: ' + keyword.value);
}
return () => ctx.parser.consume(idx, token, keyword);
}
function wrap(ctx, guard, method, cardinality) {
const gate = guard && buildPredicate(guard);
if (!cardinality) {
if (gate) {
const idx = ctx.or++;
return (args) => ctx.parser.alternatives(idx, [
{
ALT: () => method(args),
GATE: () => gate(args)
},
{
ALT: EMPTY_ALT(),
GATE: () => !gate(args)
}
]);
}
else {
return method;
}
}
if (cardinality === '*') {
const idx = ctx.many++;
return (args) => ctx.parser.many(idx, {
DEF: () => method(args),
GATE: gate ? () => gate(args) : undefined
});
}
else if (cardinality === '+') {
const idx = ctx.many++;
if (gate) {
const orIdx = ctx.or++;
// In the case of a guard condition for the `+` group
// We combine it with an empty alternative
// If the condition returns true, it needs to parse at least a single iteration
// If its false, it is not allowed to parse anything
return (args) => ctx.parser.alternatives(orIdx, [
{
ALT: () => ctx.parser.atLeastOne(idx, {
DEF: () => method(args)
}),
GATE: () => gate(args)
},
{
ALT: EMPTY_ALT(),
GATE: () => !gate(args)
}
]);
}
else {
return (args) => ctx.parser.atLeastOne(idx, {
DEF: () => method(args),
});
}
}
else if (cardinality === '?') {
const idx = ctx.optional++;
return (args) => ctx.parser.optional(idx, {
DEF: () => method(args),
GATE: gate ? () => gate(args) : undefined
});
}
else {
assertUnreachable(cardinality);
}
}
function getRule(ctx, element) {
const name = getRuleName(ctx, element);
const rule = ctx.parser.getRule(name);
if (!rule)
throw new Error(`Rule "${name}" not found."`);
return rule;
}
function getRuleName(ctx, element) {
if (isAbstractParserRule(element)) {
return element.name;
}
else if (ctx.ruleNames.has(element)) {
return ctx.ruleNames.get(element);
}
else {
let item = element;
let parent = item.$container;
let ruleName = element.$type;
while (!isParserRule(parent)) {
if (isGroup(parent) || isAlternatives(parent) || isUnorderedGroup(parent)) {
const index = parent.elements.indexOf(item);
ruleName = index.toString() + ':' + ruleName;
}
item = parent;
parent = parent.$container;
}
const rule = parent;
ruleName = rule.name + ':' + ruleName;
ctx.ruleNames.set(element, ruleName);
return ruleName;
}
}
function getToken(ctx, name) {
const token = ctx.tokens[name];
if (!token)
throw new Error(`Token "${name}" not found."`);
return token;
}
//# sourceMappingURL=parser-builder-base.js.map