xclang

CLI for common editor actions for Objective-C. xclang focuses on solving common clang integration problems into text editors. Currently projects main focus is iOS and MacOS platforms.

Problem

While it's really tempting to write Objective-C application with your favorite editor, it can be a hard task without proper syntax checker and code completion that XCode provides by default. Luckily, clang tooling can solve most of the problems and it probably used by XCode internally. Unfortunately, clang tooling requires some preparation steps and it's exposes low-level C/C++ API. xclang solves preparation steps for you and exposes simple CLI that can be integrated into your editors.

Design

xclang tries to be agnostic to the editors, but it returns results in format that is usable by popular plugins for Emacs (flycheck, company, autocomplete) and Vim(syntastic).

At this point xclang doesn't work as backend server, on the other hand it works pretty fast, in most cases latency in Emacs is barely noticeable. This can be changed in future.

Commands

At this point xclang provides this commands:

compilation-database. Serves as preparation step for other operations, it builds your project with xcodebuild CLI, parses output into Compilation Database and writes it into compile_commands.json. All other commands will try to find recursively compile_commands.json starting from current folder. You can run this command in continuous mode (--continuous), which will refresh compilation database each time you are adding new file.
syntax-check. Returns errors and warnings found in provided file. If you want to do a check on a temporary buffer (like many editor plugins do) you have to provide original buffer with -o argument, it will be used to recover compilation arguments from the compilation database.
code-complation. Returns possible completions ordered by priority (based on clang heuristics) at the specific location (-l). If you are doing completion on a temporary buffer, you have to provide -o argument. You can specify prefix (-p) that will used for filtering completion results.
goto-definition. Returns location of the definition at the specific location (-l). This command traverses translation units in the project in order to find definition, but will fallback to declaration (ex: for internal framework definitions).

Compilation

xclang is written with Rust, so you will need a Rust compiler.

In order to work properly with iOS it requires clang version that is bundled with XCode, so you will need to install XCode.

Compilation process is super simple, just run: make from the project directory. You can also run tests with make test.

xclang will be compiled to the bin folder. You may consider symlinking it to the directory that is in your PATH environment variable.

Editor Integration

Currently only Emacs integration is provided (company and flycheck). Syntastic integration for Vim may be provided. Unfortunately, I'm not aware of a good completion plugins for Vim, thus it's a bit hard to provide lightweight completion solution.

Flycheck

Syntax check for Emacs provided as a flycheck plugin, so it has to be installed. Once you have flycheck you can just load-file on the plugin file from the emacs folder.

Syntax check happens automatically for errors and warnings. If it's not happening, you may consider checking if xclang is in flycheck-checkers list. If you don't have xclang in your PATH you can set path to the xclang directly in flycheck-xclang-executable variable.

Company

Code completion for Emacs provided as a company-mode plugin. It requires yasnippet for snippet expansion. Once you have installed plugins you can load-file on the plugin file from the emacs folder, company mode and yasnippet minor mode have to be active.

If you don't have xclang in your PATH you can set path to the xclang directly in company-xclang-executable variable.

Goto Definition

Goto definition is implemented as standalone interactive function, you can find source in emacs folder. If you don't have xclang in your PATH you can set path to the xclang directly in xclang-definition-executable variable.

ap4y/xclang_tool