TextMate is a general purpose GUI text editor for MacOS released by MacroMates.
It is also a language grammar specification that is mainly used for syntax highlighting.
Supported by VSCode, Github, Sublime, Atom and of course TextMate.

TextMate has a lot of incomplete and fragmented documentation.
Hopefully this can be a comprehensive guide for VSCode's JSON TextMate.

Supported formats:

• VSCode
  • JSON .tmLanguage.json
  • XML .tmLanguage
• TextMate
  • Ascii Plist .tmLanguage (Old-style Property Lists format parser)
• Sublime
  • YAML .yaml
• Atom
  • CSON .cson
• Github-Linguist
  • JSON .json
  • XML .plist, .tmlanguage
  • YAML .yaml-tmlanguage
  • CSON .cson

TextMate is a top down line based lexer. This was done for performance reasons.
Meaning you can't match past/over new lines \n.

VSCode's TextMate grammar files use the file extension .tmLanguage.json & .tmLanguage and are located in ./extensions/publisher.extension_name.version/syntaxes/*.
TODO: Explain basics of the Package.json in relation to TextMate syntaxes.

List of TextMate engines and their Regex engines:

• VSCode - TypeScript
  • vscode-textmate v9.3.0
    • vscode-oniguruma v1.7.0
      • oniguruma v6.9.8
• TextMate v2.0 - C++
  • textmate/Onigmo v5.13.5
    • k-takata/Onigmo v5.13.5
      • oniguruma v5.9.2
• GitHub
  • Linguist
  • Lightshow/PrettyLights
    • PCRE v8.36
  • Pygments
• NovaLightshow - JavaScript
  • starry-night
    • vscode-textmate
      • vscode-oniguruma
        • oniguruma v6.9.8
• ShikiJS - TypeScript
  • @shikijs/vscode-textmate
    • @shikijs/engine-oniguruma
      • vscode-oniguruma
        • oniguruma v6.9.8
  • @shikijs/engine-javascript
    • oniguruma-to-es
      • oniguruma-parser v0.12.1
• Eclipse TM4E - Java
  • joni
• KotlinTextMate - Kotlin
  • joni
• codroid-textmate - Kotlin
  • kotlin-stdlib
• Atom - JavaScript
  • First Mate v7.4.3
    • node-oniguruma v7.2.3
      • oniguruma v5.9.6
• Arust-textmate - Rust
  • Rust Onig
• Ferroni - Rust
• tmengine - Python
• textmate-highlight - Python
• textfriend - Python
• gopher-textmate - Go

regex.tmLanguage.json.
\\K Keep effectively moves the start position of the captured text.
\\G MatchAnchor matches against the end of a begin rule.
Capture groups inside a positive-lookaround can be targeted by capture.
Capture groups inside a negative-lookaround will cause an error. Use non-capture group (?:...) instead.

embedded-languages
Todo:

• Guides
  • VSCode syntax-highlight-guide
  • VSCode embedded-languages-guide
  • TextMate 1.0 manual
  • TextMate 2.0 manual
  • Writing a TextMate Grammar: Some Lessons Learned
  • How to create syntax highlighting for VSCode
  • Building a syntax highlighting extension for VS Code
  • A guide to writing a language grammar (TextMate) in Atom
  • TextMate grammar guide
  • Scope Naming
  • Syntax Naming Conventions
  • Naming conventions for syntax scopes
  • Introducing Iro
  • Iro documentation
• Resources
  • VSCode TextMate Oniguruma regex syntax
  • TextMate Language Grammars
  • VSCode textmate_while
  • VSCode Markdown Fenced Code Block Grammar Injection Example
  • language-sampleGrammar.cson
  • Regular Expressions Quick Reference
  • Test your textmate grammars in TextMate
  • Github List: VSCode TextMate Grammar Tools
  • VSCode TmLanguage-Syntax-Highlighter Extension
  • VSCode Extensions repo
  • VSCode JSON Grammar
  • Github theme scope-previews
• Testers
  • vscode-syntax-highlighting-tester Steffeeen
  • textmate-grammar-test serkonda7
  • vscode-tmgrammar-test PanAeon
  • textmate-validate carlwr
• Playgrounds
  • NovaLightshow Nixinova
  • textmate-grammars-themes Shiki
  • phikiphp Phiki
  • oniguruma-to-es Slevithan
  • oniguruma-parser Slevithan
  • textmate-grammar-playground Youngspe
  • tmLanguage-Playground Kermanx
  • Linguist-Demo DecimalTurn
  • tmTheme-Editor Aziz
  • textmate-syntax-playground TheTarnav
  • Iro Consoli
  • TextMate Grammar Testing Tool Leskoff
• Bugs
  • Empty end matches \uFFFF
  • include grammars don't load within captures
  • Behaviour of begin/end and while patterns do not match TextMate
  • Wrong backreference escaping
  • \G matches unicode character 0xFFFF �
  • JSON key "id" breaks the tokenizer
  • JSON grammar without filePath parsed incorrectly as PList
  • Scopes on Recursive Regex Cause Problems
  • Textmate engine bug for \k<> backreferences
  • Scoping Issues For Relative Rule References
  • Absolute rule reference use local scope
  • Capturing and applying a pattern causes performance loss
  • Repository works only when it defined at top level of grammar file
  • multiply applied capture groups seems to ignore some captures
  • injections to not cover forward scoped regions
  • possible unexpected behavior from capture sub-patterns (sub-tokenized capture)
  • TextMate scope selectors: scope exclusion is not implemented
  • Format strings not being handled in grammar
  • VSCode's tmLanguage support cannot match zero-width begin and end correctly.