From 520c775c6a57a92562d7dd215f6bb20aca46d8e5 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Thu, 12 Feb 2026 00:24:39 +0000
Subject: [PATCH] Fix FindCompileCommands to handle absolute paths in
 c_build_dir_names

Use ale#path#GetAbsPath to resolve build directory paths, which correctly
handles both absolute and relative paths. When the dirname is absolute,
derive the project root from the parent of the build directory.

Co-authored-by: w0rp <3518142+w0rp@users.noreply.github.com>
---
 autoload/ale/c.vim                      | 11 +++++++--
 test/test_c_find_compile_commands.vader | 33 +++++++++++++++++++++++++
 2 files changed, 42 insertions(+), 2 deletions(-)
 create mode 100644 test/test_c_find_compile_commands.vader

diff --git a/autoload/ale/c.vim b/autoload/ale/c.vim
index bc955d0e..9ff7e697 100644
--- a/autoload/ale/c.vim
+++ b/autoload/ale/c.vim
@@ -249,11 +249,18 @@ function! ale#c#FindCompileCommands(buffer) abort
     " Search in build directories if we can't find it in the project.
     for l:path in ale#path#Upwards(expand('#' . a:buffer . ':p:h'))
         for l:dirname in ale#Var(a:buffer, 'c_build_dir_names')
-            let l:c_build_dir = l:path . s:sep . l:dirname
+            let l:c_build_dir = ale#path#GetAbsPath(l:path, l:dirname)
             let l:json_file = l:c_build_dir . s:sep . 'compile_commands.json'
 
             if filereadable(l:json_file)
-                return [l:path, l:json_file]
+                " Use the parent of the build dir for absolute
+                " paths, otherwise use the path found by searching
+                " upwards from the file.
+                let l:root = ale#path#IsAbsolute(l:dirname)
+                \   ? fnamemodify(l:c_build_dir, ':h')
+                \   : l:path
+
+                return [l:root, l:json_file]
             endif
         endfor
     endfor
diff --git a/test/test_c_find_compile_commands.vader b/test/test_c_find_compile_commands.vader
new file mode 100644
index 00000000..c24f26c0
--- /dev/null
+++ b/test/test_c_find_compile_commands.vader
@@ -0,0 +1,33 @@
+Before:
+  Save g:ale_c_build_dir_names
+
+  call ale#test#SetDirectory('/testplugin/test')
+
+After:
+  Restore
+
+  call ale#test#RestoreDirectory()
+
+Execute(FindCompileCommands should find compile_commands.json with relative build dir names):
+  call ale#test#SetFilename('test-files/c/json_project/subdir/dummy')
+
+  let g:ale_c_build_dir_names = ['build']
+
+  AssertEqual
+  \ [
+  \   ale#path#Simplify(g:dir . '/test-files/c/json_project'),
+  \   ale#path#Simplify(g:dir . '/test-files/c/json_project/build/compile_commands.json'),
+  \ ],
+  \ ale#c#FindCompileCommands(bufnr(''))
+
+Execute(FindCompileCommands should find compile_commands.json with absolute build dir names):
+  call ale#test#SetFilename('test-files/c/json_project/subdir/dummy')
+
+  let g:ale_c_build_dir_names = [ale#path#Simplify(g:dir . '/test-files/c/json_project/build')]
+
+  AssertEqual
+  \ [
+  \   ale#path#Simplify(g:dir . '/test-files/c/json_project'),
+  \   ale#path#Simplify(g:dir . '/test-files/c/json_project/build/compile_commands.json'),
+  \ ],
+  \ ale#c#FindCompileCommands(bufnr(''))