It's easy to change a lot of stuff with :substitute, but not always easy to remember patterns for more complex substitutions.

zev.vim makes it easier to apply these kind of common substitutions. For example, I might want to change:

return errors.Wrap(err, "context")
// to:
return fmt.Errorf("context: %w", err)

With zev.vim you can define patterns:

call zev#register('go', 'unwrap',
            \ 'Replace errors.Wrap() with stdlib fmt.Errorf()',
            \ '\verrors\.Wrap\((\k+), (["`])(.{-})["`]\)',
            \ 'fmt.Errorf(\2\3: %w\2, \1)')

Which can then easily be used with :Zev unwrap.

Command reference:

:Zev  name[/flags]  Apply a registered pattern; the optional [flags] are
                    passed to the :substitute command (See :help s_flags).
                    For example ":Zev errctx/c" to confirm.
:Zev! name[/flags]  Populate the commandline but don't do anything.
:Zev                List registered patterns for the current filetype.
:Zev!               List all registered patterns.

Zev defines a bunch of useful patterns (at least, useful for me) by default; use :Zev! to list them all, and let g:zev_no_default = 1 to disable this.

Please let me know if you come up with useful patterns so I can include them!

zev.vim is named after the main character in Remember. It's a good film; you should watch it.

Defining patterns

Arguments accepted by zev#register():

filetype      Filetype to register the pattern for. Separate multiple with a
              space, or use an empty string to make it available for all
              filetypes.

name          The name as used with `:Zev name`.

description   A description of what this does; not always easy to grok from
              just the pattern.

replace,      The replace and search patterns; a `:s/../../` command will
search        be built from this. Don't include the delimiters and don't
              escape `/` as `\/`, Zev will take care of this automatically

zev will put the cursor position at █ (U+2588, FULL BLOCK) in the replace pattern. You can insert this in Vim with <C-v>u2588.