Regular Expression to match TextMate Variable in for VScode Snippets

Question

Background

Hi all, I'm wokring on a VScode extension for snippets. I highlighted all $name TextMate style variables like $CURRENT_YEAR and $TM_FILENAME_BASE.

name in $name can be a integer, or a static variable.
I would also like to highlight variables like ${<INTEGER>:<DEFAULT>}, ${<INTEGER>:<DEFAULT>|<OPTIONAL_OPTIONS>} e.g. ${2:placeholder} and ${1:true|false}
Moreover, highlight transformed variables ${<STATIC_VAR>\<MATCH_REGEX>\<TRANSFORM_TARGET>\}. Example: ${TM_FILENAME/[\\.]/_/ replaces the first . with _.
All these example can be found in VScode documentation
I played Regex Golf a little, but I couldn't solve the "Balance" Chapter

Question

Is there a NEAT way to match all TextMate variables(see definition in chapter 7.2) with a Regular Expression (or other technique)?

In detail, I would want my Regex to match all $<NAME>, ${<INTEGER>:<DEFAULT>|<OPTION>}, and ${<STATIC_VAR>\<MATCH_REGEX>\<TRANSFORM_TARGET>\}

where

<NAME> can be digits and some specific letters like LINE_COMMENT;
<DEFAULT> and can be any text.
<STATIC_VAR> is some specific letters like LINE_COMMENT
<MATCH_REGEX> A regular expression, I'm not going to check if it is legal. <TRANSFORM_TARGET> The regular expression substitution output, not going to check.

My idea was to detect if there is a pair of brackets (curly parentheses). And the first word after parentheses opening is a <NAME>.

TextMate uses Oniguruma regular expression library by K. Kosako

What I've done

Match variable without {} with

match:"\\$(?:[0-9]+|TM_SELECTED_TEXT|<TYPED_ALL_POSSIBLE_NAMES>|TM_CURRENT_WORD|LINE_COMMENT)"

Tried regex pattern generator (AI)
In question Regular expression to match balanced parentheses is it said not possible in this answer
Using a dirty work-around

\\$(?= (?=<ALL_NAMES>)|{(?=<ALL_NAMES>):.+} )

Where <ALL_NAMES> represents all <NAME>s joined with pipe char |

It is not quite clear what the issue is with your "dirty" regex. What about [$](\{)?\w+(?(1)(?:\/.*})?) (demo)? — Wiktor Stribiżew
– Wiktor Stribiżew, Commented Sep 13, 2021 at 6:56
Yes! I just test it and it works beautifully. Before I worked with [regexr](regexr.com) and I knew nothing about "group conditional". By the way, your code did match the transformation but not the default value like ${1:OPT1|OPT2}, please consider add a : like this [$](\{)?\w+(?(1)(?:[\/:].+})?) (new demo)and answer the question so we can close it. — Pablo LION
– Pablo LION, Commented Sep 13, 2021 at 7:46

Wiktor Stribiżew · Accepted Answer · 2021-09-13 07:46:33Z

1

You can use a conditional construct here:

[$](\{)?\w+(?(1)(?:[\/:].*})?)

See the regex demo.

Details:

[$] - a $ char
(\{)? - an optional capturing group with ID = 1 that matches a { char
\w+ - one or more word chars
(?(1)(?:[\/:].*})?) - a conditional construct: if Group 1 matched, matches an optional sequence of a / or : and then any zero or more chars other than line break chars as many as possible up to the rightmost occurrence of a } char.

answered Sep 13, 2021 at 7:46

Wiktor Stribiżew

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4 Comments

Pablo LION Over a year ago

Sorry that I made a mistake in the code (?(1)(?:[\/:].*})?) because there should be at least 1 char after the : or /. I'm accepting this answer but I made a HUGE mistake while describing the question ... So I'm editing this question now. Please consider edit the answer accordingly. I'll finish it in <10min.

Pablo LION Over a year ago

The conditional group used here did solve most of my question and it works correctly in .tmLanguage.json for VScode.

Wiktor Stribiżew Over a year ago

@Pablion Yes, your question is a bit hectic.So, one char must be there after / or :? Then replace .* with .+.

Pablo LION Over a year ago

Feels like I squeezed too many questions in one question. So I rewrite the question to make it clearer. Huge appreciation again.

Pablo LION · Accepted Answer · 2021-09-13 12:35:01Z

Credit to Wiktor Stribiżew

The regular expression

Test demo with explanation

[$]([{])?([0-9]+)?(?(2)|(?:TM_FILENAME))(?(1)(?(2)[:].+|[\/].+[\/].*[\/])})

What does this regex do:

Match all these (legal vscode snippet variables):

$1
$21
${1:default}
${1:default|option}
$TM_FILENAME
${TM_FILENAME/[\.]/_/}
${TM_FILENAME/a//}

And match NONE of these:

${1:}
${TM_FILENAME:a|b}
${TM_FILENAME/}
${TM_FILENAME/a/}
${TM_FILENAME//abc/}
${TM_FILENAME/a//a}

full `.tmLanguage.json` fomat code

"match": "[$]({)?([0-9]+)?(?(2)|(?:TM_SELECTED_TEXT|TM_CURRENT_LINE|TM_CURRENT_WORD|TM_LINE_INDEX|TM_LINE_NUMBER|TM_FILENAME_BASE|TM_FILENAME|TM_DIRECTORY|TM_FILEPATH|RELATIVE_FILEPATH|CLIPBOARD|WORKSPACE_NAME|WORKSPACE_FOLDER|CURRENT_YEAR_SHORT|CURRENT_YEAR|CURRENT_MONTH_NAME_SHORT|CURRENT_MONTH_NAME|CURRENT_MONTH|CURRENT_DATE|CURRENT_DAY_NAME_SHORT|CURRENT_DAY_NAME|CURRENT_HOUR|CURRENT_MINUTE|CURRENT_SECONDS_UNIX|CURRENT_SECOND|RANDOM|RANDOM_HEX|UUID|BLOCK_COMMENT_START|BLOCK_COMMENT_END|LINE_COMMENT))(?(1)(?(2)[:].+|[/].+[/].*[/])})",

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Regular Expression to match TextMate Variable in for VScode Snippets

Background

Question

What I've done

2 Answers 2

4 Comments

Credit to Wiktor Stribiżew

The regular expression

What does this regex do:

full `.tmLanguage.json` fomat code

Test in VSCode

Comments

Your Answer

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Collectives™ on Stack Overflow

Background

Question

What I've done

2 Answers 2

4 Comments

Credit to Wiktor Stribiżew

The regular expression

What does this regex do:

full .tmLanguage.json fomat code

Test in VSCode

Comments

Your Answer

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full `.tmLanguage.json` fomat code