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Helm Gtags layer

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1 Description

counsel-gtags, helm-gtags and ggtags are clients for GNU Global. GNU Global is a source code tagging system that allows querying symbol locations in source code, such as definitions or references. Adding the gtags layer enables both of these modes.

1.1 Features:

  • Select any tag in a project retrieved by gtags
  • Resume previous helm-gtags session
  • Jump to a location based on context
  • Find definitions
  • Find references
  • Present tags in current function only
  • Create a tag database
  • Jump to definitions in file
  • Show stack of visited locations
  • Manually update tag database
  • Jump to next location in context stack
  • Jump to previous location in context stack
  • Jump to a file in tag database
  • Enables eldoc in modes that otherwise might not support it.
  • Enables company complete in modes that otherwise might not support it.

2 Install

2.1 GNU Global (gtags)

To use gtags, you first have to install GNU Global.

You can install global from the software repository of your OS; however, many OS distributions are out of date, and you will probably be missing support for pygments and exuberant ctags, and thus support for many languages. We recommend installing from source.

2.1.1 Install on Ubuntu

sudo apt-get install global

2.1.2 Install on OSX using Homebrew

brew install global --with-pygments --with-ctags

2.1.3 Install on *nix from source

  1. Install recommended dependencies
  2. Install with recommended features
  3. Configure your environment to use pygments and ctags

    To be able to use pygments and ctags, you need to copy the sample gtags.conf either to /etc/gtags.conf or $HOME/.globalrc. For example:

    cp gtags.conf ~/.globalrc
    

    Additionally you should define GTAGSLABEL in your shell startup file e.g. with sh/ksh:

    echo export GTAGSLABEL=pygments >> .profile
    

    With fish:

    echo export set -x GTAGSLABEL pygments >> ${HOME}/.config/fish/config.fish
    

2.1.4 Conflict between ctags and emacs's etags binary

If you installed emacs from source after ctags, your original ctags binary is probably replaced by emacs’s etags. To get around this you will need to configure emacs as following before installing:

./configure --program-transform-name='s/^ctags$/ctags.emacs/'

To check if you have the correct version of ctags execute:

ctags --version | grep Exuberant

If there is no output you have the wrong ctags executable and you need to reinstall ctags from your package manager.

2.2 Emacs Configuration

To use this configuration layer, add it to your ~/.spacemacs file. You will need to add gtags to the existing dotspacemacs-configuration-layers.

(setq dotspacemacs-configuration-layers
      '( ;; ...
        gtags
         ;; ...
        ))

2.2.1 Disabling by default

If ggtags-mode is too intrusive you can disable it by default, by setting the layer variable gtags-enable-by-default to nil.

(setq-default dotspacemacs-configuration-layers
  '((gtags :variables gtags-enable-by-default t)))

This variable can also be set as a file-local or directory-local variable for additional control on a per project basis.

3 Usage

Before using gtags, remember to create a GTAGS database by one of the following methods:

  • From within Emacs, run either counsel-gtags-create-tags or helm-gtags-create-tags, which are bound to SPC m g c. If the language is not directly supported by GNU Global, you can choose ctags or pygments as a backend to generate the database.
  • From inside a terminal:
cd /path/to/project/root

# If the language is not directly supported and GTAGSLABEL is not set
gtags --gtagslabel=pygments

# Otherwise
gtags

3.1 Language Support

3.1.1 Built-in languages

If you do not have ctags or pygments enabled gtags will only produce tags for the following languages:

  • asm
  • c/c++
  • java
  • php
  • yacc

3.1.2 Exuberant ctags languages

If you have enabled exuberant ctags and use that as the backend (i.e. GTAGSLABEL=ctags or --gtagslabel=ctags) the following additional languages are supported:

  • c#
  • erlang
  • javascript
  • common-lisp
  • emacs-lisp
  • lua
  • ocaml
  • python
  • ruby
  • scheme
  • vimscript
  • windows-scripts (.bat .cmd files)

3.1.3 Universal ctags languages

If you have installed universal ctags and use that as the backend (i.e. GTAGSLABEL=ctags or –gtagslabel=ctags) the following additional languages are supported:

  • clojure
  • d
  • go
  • rust

3.1.4 Pygments languages (plus symbol and reference tags)

In order to look up symbol references for any language not in the built in parser you must use the pygments backend. When this backend is used global actually uses both ctags and pygments to find the definitions and uses of functions and variables as well as “other symbols”.

If you enabled pygments (the best choice) and use that as the backend (i.e. GTAGSLABEL=pygments or --gtagslabel=pygments) the following additional languages will be supported:

  • elixir
  • fsharp
  • haskell
  • octave
  • racket
  • scala
  • shell-scripts
  • tex

3.2 Eldoc integration

This layer also integrates ggtags for its Eldoc feature. That means, when writing code, you can look at the minibuffer (at the bottom) and see variable and function definitions of the symbol under point. However, this feature is only activated for languages which are not:

  • C
  • C++
  • Common Lisp
  • Emacs Lisp
  • Python
  • Ruby

Since these modes have better Eldoc integration already.

In addition gtags commands are also supported for symbols in the compile, shell-command and async-shell-command buffers.

4 Key bindings

Key binding Description
g d jump to definition or references of selected tag

4.1 Helm

Key binding Description
SPC m g C create a tag database
SPC m g f jump to a file in tag database
SPC m g g jump to a location based on context
SPC m g G jump to a location based on context (open another window)
SPC m g d find definitions
SPC m g i present tags in current function only
SPC m g l jump to definitions in file
SPC m g n jump to next location in context stack
SPC m g p jump to previous location in context stack
SPC m g r find references
SPC m g R resume previous helm-gtags session
SPC m g s select any tag in a project retrieved by gtags
SPC m g S show stack of visited locations
SPC m g y find symbols
SPC m g u manually update tag database

4.2 Ivy

counsel-gtags is currently missing a few minor features compared to helm-gtags.

Key binding Description
SPC m g C create a tag database
SPC m g f jump to a file in tag database
SPC m g g jump to a location based on context
SPC m g d find definitions
SPC m g n jump to next location in context stack
SPC m g p jump to previous location in context stack
SPC m g r find references
SPC m g s select any tag in a project retrieved by gtags
SPC m g y find symbols
SPC m g u manually update tag database

Author: Travis CI User

Created: 2019-01-22 Tue 20:42

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