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I have created a guard snippet (ultisnips) in order to add on my existing functions:

snippet guard "add guard to functions" b
if !exists('*${1:func_name}')
   ${VISUAL}
endif
${0:jump here <C-j>}
endsnippet

At the moment I have to type the "func_name" at the top and it has to be equal at the name captured in the visual section, anyone have a better suggestion or any improvement to this?

1 Answer 1

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Try this:

snippet guard "add guard to functions" b
if !exists('*`!p snip.rv = re.search('\S+\s+(\S+)\(', snip.v.text.splitlines()[0]).group(1)`')
    ${VISUAL}
endif
${0:jump here <C-j>}
endsnippet

The `!p snip.rv = ...` part is a python interpolation. The evaluation of the expression to the right of the assignment operator after snip.rv replaces everything between the backticks.

Here the expression is:

re.search('\S+\s+(\S+)\(', snip.v.text.splitlines()[0]).group(1)
  • snip.v.text allows you to refer to the last visually-selected text in a python interpolation.
  • .splitlines() allows you to split the lines of the visual selection in a list.

  • snip.v.text.splitlines()[0] grabs the first line in the selection.

  • re.search('\S+\s+(\S+)\(', ...).group(1) extracts the function name from this line.

If you make a mistake when selecting the function, the first line may not match the regex, in which case an error will be raised.

Inside the python interpolation, you can use a try, except construct to catch the error:

snippet guard "add guard to functions" b
if !exists('*`!p
try:
    func_name = re.search('\S+\s+(\S+)\(', snip.v.text.splitlines()[0]).group(1)
except AttributeError:
    func_name = ''
snip.rv = func_name
`')
    ${VISUAL}
endif
${0:jump here <C-j>}
endsnippet
1
  • The regex could be less permissive? While a function could be function or fun or functi, it must start with fu, so you could instead use r'\bfu\S*\s+(\S+)\(' to ensure it starts with 'fu' (and \b to prevent matching something like :Snafu). (There's lots of other possibilities for false positives, but this seems like the most important fix.)
    – idbrii
    May 13, 2019 at 23:39

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