From 6cfca21bac6bb39b50cba1c23ffb2b69e2d94df8 Mon Sep 17 00:00:00 2001
From: Christian Clason <c.clason@uni-graz.at>
Date: Tue, 2 Apr 2024 10:54:40 +0200
Subject: [PATCH] feat(treesitter): add `@injection.filename`

Problem: Injecting languages for file redirects (e.g., in bash) is not
possible.

Solution: Add `@injection.filename` capture that is piped through
`vim.filetype.match({ filename = node_text })`; the resulting filetype
(if not `nil`) is then resolved as a language (either directly or
through the list maintained via `vim.treesitter.language.register()`).

Note: `@injection.filename` is a non-standard capture introduced by
Helix; having two editors implement it makes it likely to be upstreamed.
---
 runtime/doc/news.txt                        | 3 +++
 runtime/doc/treesitter.txt                  | 4 ++++
 runtime/lua/vim/treesitter/languagetree.lua | 4 ++++
 3 files changed, 11 insertions(+)

diff --git a/runtime/doc/news.txt b/runtime/doc/news.txt
index e39cf95da9..5aa274637b 100644
--- a/runtime/doc/news.txt
+++ b/runtime/doc/news.txt
@@ -240,6 +240,9 @@ The following new APIs and features were added.
     language aliases (e.g., filetype or custom shorthands) registered via
     |vim.treesitter.language.register()| and/or attempt lower case variants of
     the text.
+  • `@injection.filename` will try to match the node text via
+    |vim.filetype.match()| and treat the result as a language name in the same
+    way as `@injection.language`.
   • The `#set!` directive now supports `injection.self` and `injection.parent`
     for injecting either the current node's language or the parent
     |LanguageTree|'s language, respectively.
diff --git a/runtime/doc/treesitter.txt b/runtime/doc/treesitter.txt
index 0d5511ac40..2356a0c235 100644
--- a/runtime/doc/treesitter.txt
+++ b/runtime/doc/treesitter.txt
@@ -654,6 +654,10 @@ parent tree. The language injection query allows you to specify these
     • `@injection.language` - indicates that the captured node’s text may
       contain the name of a language that should be used to re-parse the
       `@injection.content`.
+    • `@injection.filename` - indicates that the captured node’s text may
+      contain a filename; the corresponding filetype is then looked-up up via
+      |vim.filetype.match()| and treated as the name of a language that should
+      be used to re-parse the `@injection.content`.
 
 The language injection behavior can also be configured by some properties
 associated with patterns:
diff --git a/runtime/lua/vim/treesitter/languagetree.lua b/runtime/lua/vim/treesitter/languagetree.lua
index 3b5d8953c9..8f65cb57c3 100644
--- a/runtime/lua/vim/treesitter/languagetree.lua
+++ b/runtime/lua/vim/treesitter/languagetree.lua
@@ -809,6 +809,10 @@ function LanguageTree:_get_injection(match, metadata)
       if name == 'injection.language' then
         local text = vim.treesitter.get_node_text(node, self._source, { metadata = metadata[id] })
         lang = resolve_lang(text)
+      elseif name == 'injection.filename' then
+        local text = vim.treesitter.get_node_text(node, self._source, { metadata = metadata[id] })
+        local ft = vim.filetype.match({ filename = text })
+        lang = ft and resolve_lang(ft)
       elseif name == 'injection.content' then
         ranges = get_node_ranges(node, self._source, metadata[id], include_children)
       end