Add Clangd language server support for C

6 files changed, 83 insertions, 2 deletions

diff --git a/README.md b/README.md
index 99ea73ed..66a30bf2 100644
--- a/README.md
+++ b/README.md
@@ -97,7 +97,7 @@ formatting.
 | Awk | [gawk](https://www.gnu.org/software/gawk/)|
 | Bash | [language-server](https://github.com/mads-hartmann/bash-language-server), shell [-n flag](https://www.gnu.org/software/bash/manual/bash.html#index-set), [shellcheck](https://www.shellcheck.net/), [shfmt](https://github.com/mvdan/sh) |
 | Bourne Shell | shell [-n flag](http://linux.die.net/man/1/sh), [shellcheck](https://www.shellcheck.net/), [shfmt](https://github.com/mvdan/sh) |
-| C | [cppcheck](http://cppcheck.sourceforge.net), [cpplint](https://github.com/google/styleguide/tree/gh-pages/cpplint), [clang](http://clang.llvm.org/), [clangtidy](http://clang.llvm.org/extra/clang-tidy/) !!, [clang-format](https://clang.llvm.org/docs/ClangFormat.html), [flawfinder](https://www.dwheeler.com/flawfinder/), [gcc](https://gcc.gnu.org/) |
+| C | [cppcheck](http://cppcheck.sourceforge.net), [cpplint](https://github.com/google/styleguide/tree/gh-pages/cpplint), [clang](http://clang.llvm.org/), [clangd](https://clang.llvm.org/extra/clangd.html), [clangtidy](http://clang.llvm.org/extra/clang-tidy/) !!, [clang-format](https://clang.llvm.org/docs/ClangFormat.html), [flawfinder](https://www.dwheeler.com/flawfinder/), [gcc](https://gcc.gnu.org/) |
 | C++ (filetype cpp) | [clang](http://clang.llvm.org/), [clangcheck](http://clang.llvm.org/docs/ClangCheck.html) !!, [clangtidy](http://clang.llvm.org/extra/clang-tidy/) !!, [clang-format](https://clang.llvm.org/docs/ClangFormat.html), [cppcheck](http://cppcheck.sourceforge.net), [cpplint](https://github.com/google/styleguide/tree/gh-pages/cpplint) !!, [cquery](https://github.com/cquery-project/cquery), [flawfinder](https://www.dwheeler.com/flawfinder/), [gcc](https://gcc.gnu.org/) |
 | CUDA | [nvcc](http://docs.nvidia.com/cuda/cuda-compiler-driver-nvcc/index.html) |
 | C# | [mcs](http://www.mono-project.com/docs/about-mono/languages/csharp/) see:`help ale-cs-mcs` for details, [mcsc](http://www.mono-project.com/docs/about-mono/languages/csharp/) !! see:`help ale-cs-mcsc` for details and configuration|
diff --git a/ale_linters/c/clangd.vim b/ale_linters/c/clangd.vim
new file mode 100644
index 00000000..5aa2e221
--- /dev/null
+++ b/ale_linters/c/clangd.vim
@@ -0,0 +1,29 @@
+" Author: Andrey Melentyev <andrey.melentyev@protonmail.com>
+" Description: Clangd language server
+
+call ale#Set('c_clangd_executable', 'clangd')
+call ale#Set('c_clangd_options', '')
+
+function! ale_linters#c#clangd#GetProjectRoot(buffer) abort
+    let l:project_root = ale#path#FindNearestFile(a:buffer, 'compile_commands.json')
+    return !empty(l:project_root) ? fnamemodify(l:project_root, ':h') : ''
+endfunction
+
+function! ale_linters#c#clangd#GetExecutable(buffer) abort
+    return ale#Var(a:buffer, 'c_clangd_executable')
+endfunction
+
+function! ale_linters#c#clangd#GetCommand(buffer) abort
+    let l:executable = ale_linters#c#clangd#GetExecutable(a:buffer)
+    let l:options = ale#Var(a:buffer, 'c_clangd_options')
+
+    return ale#Escape(l:executable) . (!empty(l:options) ? ' ' . l:options : '')
+endfunction
+
+call ale#linter#Define('c', {
+\   'name': 'clangd',
+\   'lsp': 'stdio',
+\   'executable_callback': 'ale_linters#c#clangd#GetExecutable',
+\   'command_callback': 'ale_linters#c#clangd#GetCommand',
+\   'project_root_callback': 'ale_linters#c#clangd#GetProjectRoot',
+\})
diff --git a/doc/ale-c.txt b/doc/ale-c.txt
index c41f3bc8..acff722c 100644
--- a/doc/ale-c.txt
+++ b/doc/ale-c.txt
@@ -64,6 +64,25 @@ g:ale_c_clang_options                                   *g:ale_c_clang_options*
 
 
 ===============================================================================
+clangd                                                           *ale-c-clangd*
+
+g:ale_c_clangd_executable                           *g:ale_c_clangd_executable*
+                                                    *b:ale_c_clangd_executable*
+  Type: |String|
+  Default: `'clangd'`
+
+  This variable can be changed to use a different executable for clangd.
+
+
+g:ale_c_clangd_options                                 *g:ale_c_clangd_options*
+                                                       *b:ale_c_clangd_options*
+  Type: |String|
+  Default: `''`
+
+  This variable can be changed to modify flags given to clangd.
+
+
+===============================================================================
 clang-format                                                *ale-c-clangformat*
 
 g:ale_c_clangformat_executable                 *g:ale_c_clangformat_executable*
diff --git a/doc/ale.txt b/doc/ale.txt
index 1a75c29c..8182c27a 100644
--- a/doc/ale.txt
+++ b/doc/ale.txt
@@ -26,6 +26,7 @@ CONTENTS                                                         *ale-contents*
       gawk................................|ale-awk-gawk|
     c.....................................|ale-c-options|
       clang...............................|ale-c-clang|
+      clangd..............................|ale-c-clangd|
       clang-format........................|ale-c-clangformat|
       clangtidy...........................|ale-c-clangtidy|
       cppcheck............................|ale-c-cppcheck|
@@ -335,7 +336,7 @@ Notes:
 * Awk: `gawk`
 * Bash: `language-server`, `shell` (-n flag), `shellcheck`, `shfmt`
 * Bourne Shell: `shell` (-n flag), `shellcheck`, `shfmt`
-* C: `cppcheck`, `cpplint`!!, `clang`, `clangtidy`!!, `clang-format`, `flawfinder`, `gcc`
+* C: `cppcheck`, `cpplint`!!, `clang`, `clangd`, `clangtidy`!!, `clang-format`, `flawfinder`, `gcc`
 * C++ (filetype cpp): `clang`, `clangcheck`!!, `clangtidy`!!, `clang-format`, `cppcheck`, `cpplint`!!, `cquery`, `flawfinder`, `gcc`
 * CUDA: `nvcc`!!
 * C#: `mcs`, `mcsc`!!
diff --git a/test/command_callback/clangd_paths/compile_commands.json b/test/command_callback/clangd_paths/compile_commands.json
new file mode 100644
index 00000000..e69de29b
--- /dev/null
+++ b/test/command_callback/clangd_paths/compile_commands.json
diff --git a/test/command_callback/test_c_clangd_command_callbacks.vader b/test/command_callback/test_c_clangd_command_callbacks.vader
new file mode 100644
index 00000000..c8c10b67
--- /dev/null
+++ b/test/command_callback/test_c_clangd_command_callbacks.vader
@@ -0,0 +1,32 @@
+Before:
+  call ale#assert#SetUpLinterTest('c', 'clangd')
+
+  Save &filetype
+  let &filetype = 'c'
+
+After:
+  call ale#assert#TearDownLinterTest()
+
+Execute(The language string should be correct):
+  AssertLSPLanguage 'c'
+
+Execute(The default executable should be correct):
+  AssertLinter 'clangd', ale#Escape('clangd')
+
+Execute(The project root should be detected correctly):
+  AssertLSPProject ''
+
+  call ale#test#SetFilename('clangd_paths/dummy.c')
+
+  AssertLSPProject ale#path#Simplify(g:dir . '/clangd_paths')
+
+Execute(The executable should be configurable):
+  let g:ale_c_clangd_executable = 'foobar'
+
+  AssertLinter 'foobar', ale#Escape('foobar')
+
+Execute(The options should be configurable):
+  let b:ale_c_clangd_options = '-compile-commands-dir=foo'
+
+  AssertLinter 'clangd', ale#Escape('clangd') . ' ' . b:ale_c_clangd_options
+