Debugging With Vim Go

l-lin included in post

2020-02-10 341 words 2 minutes

Although learning VIM can be quite painful, I learned it and now I love it so much I can’t write or code without it. Unfortunately, VIM is not super intuitive and is not as user friendly as modern IDEs. Some functionalities are not easy to use and / or easy to find. For example, debugging programs using VIM is not as trivial as clicking on a button like most IDEs.

In this post, I will show some basic commands to use to debug a Go program with vim-go.

Start the debugger by using :GoDebugStart in your main function. Your VIM should display the following:

Your buffer will be split with new windows:

stacktrace
variables
goroutine
output of stdout/stderr

Those windows display interesting information, but for my daily usage, I don’t need to have all those windows. I just keep the variable and stacktrace windows. To do so, I edited my .vimrc file to include the following:

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let g:go_debug_windows = {
      \ 'vars':       'rightbelow 60vnew',
      \ 'stack':      'rightbelow 10new',
\ }

If you want to start with argument or some flag, you can do it by calling :GoDebugStart . -someflag value. In my example, I execute with :GoDebugStart . -name Louis

Then, place your cursor under the line you want to break and call :GoDebugNext. This will add a breakpoint, run your program and halt on the breakpoint:

You can see the values of the local variables as well as the function argument’s values.

You can also print in the stdout with :GoDebugPrint variable if the variable is not displayed in the variable window (e.g. the value of a pointer, one element in a slice, …):

You can navigate and put a breakpoint anywhere you want. For example, I call :GoDebugNext inside my function greet:

When you have finished, you can call :GoDebugStop to stop the debugging.

A GIF to show the entire debugging of a simple Go program:

If you want to go further, you can check the documentation in VIM with :h vim-go or directly online.