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87 lines
2.8 KiB
JavaScript
87 lines
2.8 KiB
JavaScript
// @flow
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import {Token} from "./Token";
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import type {AnyParseNode} from "./parseNode";
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/**
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* This is the ParseError class, which is the main error thrown by KaTeX
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* functions when something has gone wrong. This is used to distinguish internal
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* errors from errors in the expression that the user provided.
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*
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* If possible, a caller should provide a Token or ParseNode with information
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* about where in the source string the problem occurred.
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*/
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class ParseError {
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name: "ParseError";
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position: number | void;
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// Error start position based on passed-in Token or ParseNode.
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length: number | void;
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// Length of affected text based on passed-in Token or ParseNode.
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rawMessage: string | void;
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// The underlying error message without any context added.
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constructor(
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message: string, // The error message
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token?: ?Token | AnyParseNode, // An object providing position information
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): ParseError {
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let error = "KaTeX parse error: " + message;
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let start;
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let end;
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const loc = token && token.loc;
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if (loc && loc.start <= loc.end) {
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// If we have the input and a position, make the error a bit fancier
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// Get the input
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const input = loc.lexer.input;
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// Prepend some information
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start = loc.start;
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end = loc.end;
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if (start === input.length) {
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error += " at end of input: ";
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} else {
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error += " at position " + (start + 1) + ": ";
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}
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// Underline token in question using combining underscores
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const underlined = input.slice(start, end).replace(/[^]/g, "$&\u0332");
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// Extract some context from the input and add it to the error
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let left;
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if (start > 15) {
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left = "…" + input.slice(start - 15, start);
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} else {
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left = input.slice(0, start);
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}
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let right;
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if (end + 15 < input.length) {
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right = input.slice(end, end + 15) + "…";
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} else {
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right = input.slice(end);
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}
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error += left + underlined + right;
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}
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// Some hackery to make ParseError a prototype of Error
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// See http://stackoverflow.com/a/8460753
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// $FlowFixMe
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const self: ParseError = new Error(error);
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self.name = "ParseError";
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// $FlowFixMe
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self.__proto__ = ParseError.prototype;
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self.position = start;
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if (start != null && end != null) {
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self.length = end - start;
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}
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self.rawMessage = message;
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return self;
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}
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}
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// $FlowFixMe More hackery
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ParseError.prototype.__proto__ = Error.prototype;
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export default ParseError;
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