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* @license Apache-2.0
*
* Copyright (c) 2019 The Stdlib Authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
'use strict';
// MODULES //
var logger = require( 'debug' );
var tokTypes = require( 'acorn' ).tokTypes;
var inherit = require( '@stdlib/utils/inherit' );
// VARIABLES //
var debug = logger( 'repl:acorn:detect_multiline_input' );
// Define a regular expression for matching allowed line terminators ( see https://www.ecma-international.org/ecma-262/#sec-line-terminators):
var RE_SEC_LINE_TERMINATORS = /\\(?:\r\n?|\n|\u2028|\u2029)$/;
// Define a regular expression for match a code string whose first non-whitespace character is an opening brace `{`:
var RE_OPENING_BRACE = /^\s*\{/;
// MAIN //
/**
* Acorn plugin which detects whether a user is attempting to enter multi-line input.
*
* ## Notes
*
* - Detection attempts to determine whether an error originates at the **end** of command input. This can happen under two circumstances:
*
* 1. Any error raised after encountering an `eof` token.
*
* 2. Three scenarios where tokens can legally span multiple lines:
*
* - templates
* - comments
* - string literals with a backslash at the end of a line, thus indicating a continuation
*
* - We specifically look for 'unterminated' errors (and not, e.g., syntax errors in a template `${}` expression).
*
* - Currently, the only means to detect 'unterminated' errors is by examining acorn's error messages. Should these error messages change, this plugin **needs** to be updated.
*
* @private
* @param {Function} Parser - Parser class
* @returns {Function} extended class constructor
*/
function plugin( Parser ) {
/**
* Custom parser constructor.
*
* @private
* @param {...*} args - arguments
* @returns {CustomParser} custom parser
*/
function CustomParser() {
var args;
var i;
args = [];
for ( i = 0; i < arguments.length; i++ ) {
args.push( arguments[ i ] );
}
Parser.apply( this, args );
// Initialize a flag for determining whether a parse error originates from attempting to enter a multi-line command:
this.HAS_MULTILINE_ERROR = false;
return this;
}
/**
* Inherit from the `Parser` prototype.
*/
inherit( CustomParser, Parser );
/**
* Reads the next token.
*
* @private
* @name nextToken
* @memberof CustomParser.prototype
* @type {Function}
*/
CustomParser.prototype.nextToken = function nextToken() { // eslint-disable-line no-restricted-syntax
Parser.prototype.nextToken.call( this );
if ( this.type === tokTypes.eof ) {
debug( 'Detected an error after an `eof` token.' );
this.HAS_MULTILINE_ERROR = true;
}
};
/**
* Raises an exception upon encountering a parse error.
*
* @private
* @name raise
* @memberof CustomParser.prototype
* @type {Function}
* @param {number} pos - position
* @param {string} message - message
*/
CustomParser.prototype.raise = function raise( pos, message ) { // eslint-disable-line no-restricted-syntax
var token;
switch ( message ) {
case 'Unterminated template':
debug( 'Detected an error due to an unterminated template.' );
this.HAS_MULTILINE_ERROR = true;
break;
case 'Unterminated comment':
debug( 'Detected an error due to an unterminated comment.' );
this.HAS_MULTILINE_ERROR = true;
break;
case 'Unterminated string constant':
token = this.input.slice( this.lastTokStart, this.pos );
this.HAS_MULTILINE_ERROR = RE_SEC_LINE_TERMINATORS.test( token );
if ( this.HAS_MULTILINE_ERROR ) {
debug( 'Detected an error due to an unterminated string constant.' );
}
break;
default:
break;
}
Parser.prototype.raise.call( this, pos, message );
};
/**
* Asserts whether parsing fails due to incomplete statements/expressions spanning multiple lines.
*
* @private
* @name hasMultilineError
* @memberof CustomParser.prototype
* @type {Function}
* @returns {boolean} boolean indicating whether parsing fails due to incomplete multi-line statements/expressions
*/
CustomParser.prototype.hasMultilineError = function hasMultilineError() { // eslint-disable-line no-restricted-syntax
var code;
// Reset the error flag BEFORE parsing:
this.HAS_MULTILINE_ERROR = false;
// Check for code which we want evaluated as an expression, rather than a block, such as an object literal (e.g., `{'a':1}`)...
if ( RE_OPENING_BRACE.test( this.input ) ) {
// Only prepend an open parenthesis as the goal is to test for potentially valid but incomplete expressions:
code = '(' + this.input;
// First try parsing as a partially wrapped expression...
debug( 'Attempting to parse as a wrapped expression...' );
if ( CustomParser.hasMultilineError( code, this.options ) ) {
return true;
}
// Now try parsing as an unwrapped expression...
}
// Try to parse the code...
try {
this.parse( this.input );
debug( 'Successfully parsed code. No multi-line error detected.' );
return false;
} catch ( error ) {
debug( 'Unable to parse code.' );
debug( 'Error: %s', error.message );
if ( this.HAS_MULTILINE_ERROR ) {
debug( 'Detected a multi-line error.' );
}
return this.HAS_MULTILINE_ERROR;
}
};
/**
* Asserts whether an unevaluated code string contains an error due to incomplete statements/expressions spanning multiple lines.
*
* @private
* @name hasMultilineError
* @memberof CustomParser
* @type {Function}
* @param {string} input - code to test
* @param {Object} [options] - options
* @returns {boolean} boolean indicating whether a provided code string has incomplete multi-line statements/expressions
*/
CustomParser.hasMultilineError = function hasMultilineError( input, options ) { // eslint-disable-line no-restricted-syntax, max-len
return new CustomParser( options, input ).hasMultilineError();
};
return CustomParser;
}
// EXPORTS //
module.exports = plugin;
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