Allow dynamic location of textmate grammar

Ref: https://github.com/vuejs/vetur/issues/210

In Vue files you can have <template>, <style> and <script> tag.

However, certain libraries can add top-level custom blocks that uses another language. For example:

<template></template>
<script></script>
<style></style>

<docs>
# This might be markdown or json, depending on user's build configuration
</docs>

Our approach was:

• Give a setting vetur.grammar.customBlocks
• Register a command to recompile the TextMate grammar with the custom blocks
• Write the file to extension directory, the same path as the one specified in package.json

This has been working, but I’m worried extension integrity check might kick in and ask for reinstall. Also @sandy081 mentioned updates remove the old folder, so it’s bad to keep states in extension directory.

What I need is a path that I can:

• Statically determine in write-time (as the path is specified in package.json)
• Have write permission

So the paths in ExtensionContext wouldn’t work for me.

After checking with @sandy081, we think offering an API like languages.setGrammar would be best. We considered allowing path interpolations like ${globalStoragePath}/grammars/vue.json in package.json, but that means the best Vetur can do is to write to that path on first activation, so no coloring before first activation/reload.

However, I’m not sure we should provide an API tied to TextMate grammar. Also the API means the dynamically generated TextMate grammar wouldn’t be loaded until extension activation.

@alexandrudima What do you think?

[mechatroner]

I wanted to open a new ticket, but found the existing one! I also have a strong need for dynamic grammar generation. As a developer of Rainbow CSV I need this API to implement the following features:

• Support comments in CSV files (depending on user selection of a comment prefix Rainbow CSV would be able to generate an appropriate TextMate grammar)
• Support all possible single-character and multi-character CSV delimiters (just the ASCII character set has over 30 non-alphanumeric characters that can be used as CSV separators, so providing 30 pre-generated static syntax files is not feasible, and there are also use-cases for multi-character separators) There are multiple issues in my project which are blocked by the lack of this mechanism in VSCode: mechatroner/vscode_rainbow_csv#14, mechatroner/vscode_rainbow_csv#1, mechatroner/vscode_rainbow_csv#31, mechatroner/vscode_rainbow_csv#70, mechatroner/vscode_rainbow_csv#58, mechatroner/vscode_rainbow_csv#33

Both Vim and Sublime Text 3 editors support dynamic syntax generation; this mechanism is widely used in Vim by parenthesis highlighting extensions.

[jquense]

any chance semantic highlighting could hackily cover this? https://code.visualstudio.com/api/language-extensions/semantic-highlight-guide