Stage 3 Draft / November 29, 2018

Hashbang Grammar for JS

Introduction

This document attempts to introduce a grammar production for the common interpreter directive syntax that occurs in command-line application usage.

1Syntax

1.1ECMAScript Language: Lexical Grammar

The source text of an ECMAScript Script or Module is first converted into a sequence of input elements, which are tokens, line terminators, comments, or white space. The source text is scanned from left to right, repeatedly taking the longest possible sequence of code points as the next input element.

There are several situations where the identification of lexical input elements is sensitive to the syntactic grammar context that is consuming the input elements. This requires multiple goal symbols for the lexical grammar. The InputElementHashbangOrRegExp is used as the first token of the Script and Module syntactic grammar contexts. The InputElementRegExpOrTemplateTail goal is used in syntactic grammar contexts where a RegularExpressionLiteral, a TemplateMiddle, or a TemplateTail is permitted. The InputElementRegExp goal symbol is used in all syntactic grammar contexts where a RegularExpressionLiteral is permitted but neither a TemplateMiddle, nor a TemplateTail is permitted. The InputElementTemplateTail goal is used in all syntactic grammar contexts where a TemplateMiddle or a TemplateTail is permitted but a RegularExpressionLiteral is not permitted. In all other contexts, InputElementDiv is used as the lexical goal symbol.

InputElementHashbangOrRegExp::HashbangComment WhiteSpace LineTerminator Comment CommonToken RightBracePunctuator RegularExpressionLiteral

Hashbang Comments

Hashbang Comments are location-sensitive and like other types of comments are discarded from the stream of input elements for the syntactic grammar.

HashbangComment::#!SingleLineCommentCharsopt

ACopyright & Software License

Copyright Notice

© 2018 Bradley Farias

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