Snippet transforms do not handle regex with alternatives or optional matches

[dogoku]

• VSCode Version: v1.17
• OS Version: N/A

Snippet transform functions (/upcase, /downcase, /capitalize) do not apply to optional capture groups, such as in case of a regex with alternatives, e.g. the regex in the example below (explanation). Instead the matches get replaced by the literal strings (i.e the string "/upcase").

I had a look at the grammar and it seems that the EBNF does not specify what if and else mean for the format rule, so I guess the implementation is not technically "wrong". But given that your intention for this feature is to be compatible with TM and ST snippets, then I see this as a bug, since this is possible in ST (albeit with a different format syntax).

---

Steps to Reproduce:

1. Add the following snippet to your js user snippets

"Class name": {
    "prefix": "hclass",
    "body": "${1:${TM_FILENAME/^(.)|(?:-(.))|(\\.js)/${1:+/upcase}${2:+/upcase}/g}}",
    "description": "Converts a hyphenated filename to a class name"
}

2. Open a js file with a hyphenated name, e.g my-awesome-module.js
3. Type hclass and expand the snippet

Expected result: MyAwesomeModule
Actual result: /upcasey/upcasewesome/upcaseodule

[MartynasZilinskas]

I was looking how to change from kebab-case to PascalCase too. This would be really nice to have.

[jrieken]

Yeah, there is something off. It should be ${1:/upcase} and not ${1:+/upcase} but it still won't work... I'll investigate. Maybe using String#replace isn't enough

[dogoku]

I used the ${1:+/upcase} because the regex has alternate cases, so the group I am trying to replace might not match each case (it's a global regex, so it will match multiple times). I had to do the same thing for the ST version as well, i.e: (?1\u$1:)(?2\u$2:)

Actually i tried ${1:/upcase} as well, when the first one didn't work, but it throws an exception, cause it cant replace something undefined, which makes sense if you think about it.

[jrieken]

Yeah, /upcase et al need to be smarter. And the whole regex evaluation needs to be a little smarter... Thanks for this issue btw, without a real spec it's kinda hard to get this right in the first place. This is spec by sample ;-)

[dogoku]

Let me know if I can help in some way. I haven't looked at the code at all, but I'm willing to help out. Thx

[ashclarke]

I'm trying to do something similar with CapitalCase filename -> kebab-case.

I have ${TM_FILENAME_BASE/([A-Z][a-z]+)([A-Z][a-z]+$)?/$1-$2/g} but no way to downcase it after.

I tried wrapping it with another variable but get an Invalid Arguments warning.

${templatepath:${TM_FILENAME_BASE/([A-Z][a-z]+)([A-Z][a-z]+$)?/$1-$2/g}/downcase}

and this result:

Capital-Case-Name/downcase

I'm not sure if I've just read the capability of this wrong, or if something is missing in VS Code.

[jrieken]

@dogoku I have pushed changes to make the format string smarter (that means not explode when having no match). You can now use this pattern: ${TM_FILENAME/^(.)|(?:-(.))|(\\.js)/${1:/upcase}${2:/upcase}/g}, which is also how it works in Textmate itself.

@ashclarke You need to apply the /downcase function on the match, so ${1:/downcase} etc. Check out: e8f088d

[ashclarke]

Thanks @jrieken - I will check it out!

[dogoku]

Thanks @jrieken, is this patch available in Insider's build?

[jrieken]

Yeah, should be available with todays insiders build

[dogoku]

@jrieken Sorry to do this again, but I found another bug :(

In the latest insiders build (v1.18.0-86e057cd), transforms are working for optional matches, however not all the transforms are applied if you reused the same variable (e.g $1) in other parts of the snippet.

Given the following simplified example:

//TM_FILENAME_BASE: `my-awesome-module`
[
"function ${1:${TM_FILENAME_BASE/^(.)|-(.)/${1:/upcase}${2:/upcase}/gm}} () {}",
"module.exports = $1;"
]

//Expected
function MyAwesomeModule () {}
module.exports = MyAwesomeModule;

//Actual
function MyAwesomeModule () {}
module.exports = My-awesome-module;

In case you missed it, the second use of $1 was not transformed properly, having only the first transform applied to it ${1:/upcase}, where as the second transform ${2:/upcase} was not applied at all, resulting in the string My-awesome-module instead of MyAwesomeModule

Should I open a new ticket for this?

[ashclarke]

I noticed this too, before, but it isn’t limited to the insiders build. I noticed it happen in the latest stable release.

[jrieken]

Sorry to do this again, but I found another bug :(

Nothing to be sorry about except for not filing a new issue.

[dogoku]

Nothing to be sorry about except for not filing a new issue

No worries @jrieken here you go: #37702