[mini.ai] The perfect mini-word textobject

[Bvngee]

In the mini.ai help file, there's this custom textobject example:

-- Word with camel case support:
{
  {
    '%u[%l%d]+%f[^%l%d]',
    '%f[%S][%l%d]+%f[^%l%d]',
    '%f[%P][%l%d]+%f[^%l%d]',
    '^[%l%d]+%f[^%l%d]',
  },
  '^().*()$'
}

I absolutely love this textobject and use it to rename variables/functions all the time. However, it has problems:

• breaks with SNAKE_CASE_IN_UPPERCASE
• doesn't work with some instances of Snake_Case_Titlecase (i.e. single-letter words)
• supports regular standalone lowercase words, but not uppercase ones
• worst of all: There's no comments or explanations and it looks like Egyptian hieroglyphics.

So, here's my updated version that fixes these issues with sufficient comments. It supports, as far as I can tell, all text cases and capitalizations:

-- snake_case, camelCase, PascalCase, etc; all capitalizations
{
  -- Lua 5.1 character classes and the undocumented frontier pattern:
  -- https://www.lua.org/manual/5.1/manual.html#5.4.1
  -- http://lua-users.org/wiki/FrontierPattern
  -- note: when I say "letter" I technically mean "letter or digit"
  {
    -- Matches a single uppercase letter followed by 1+ lowercase letters.
    -- This covers:
    -- - PascalCaseWords (or the latter part of camelCaseWords)
    '%u[%l%d]+%f[^%l%d]', -- An uppercase letter, 1+ lowercase letters, to end of lowercase letters

    -- Matches lowercase letters up until not lowercase letter.
    -- This covers:
    -- - start of camelCaseWords (just the `camel`)
    -- - snake_case_words in lowercase
    -- - regular lowercase words
    '%f[^%s%p][%l%d]+%f[^%l%d]', -- after whitespace/punctuation, 1+ lowercase letters, to end of lowercase letters
    '^[%l%d]+%f[^%l%d]', -- after beginning of line, 1+ lowercase letters, to end of lowercase letters

    -- Matches uppercase or lowercase letters up until not letters.
    -- This covers:
    -- - SNAKE_CASE_WORDS in uppercase
    -- - Snake_Case_Words in titlecase
    -- - regular UPPERCASE words
    -- (it must be both uppercase and lowercase otherwise it will
    -- match just the first letter of PascalCaseWords)
    '%f[^%s%p][%a%d]+%f[^%a%d]', -- after whitespace/punctuation, 1+ letters, to end of letters
    '^[%a%d]+%f[^%a%d]', -- after beginning of line, 1+ letters, to end of letters 
  },
  '^().*()$',
}

Trust me, you will not regret this. This is one of the biggest quality-of-life improvements I've had with vim editing yet. Take a look:

perfect-textobj.mp4

[Bvngee]

I'd be interested to hear if anyone thinks the regex can be simplified. It took me quite a while to understand what it was doing (especially the %f pattern) but I could very likely be missing some opportunity for further improvement.

[echasnovski]

I'd be interested to hear if anyone thinks the regex can be simplified. It took me quite a while to understand what it was doing (especially the %f pattern) but I could very likely be missing some opportunity for further improvement.

One thing comes to mind: [%a%d] set (all letters and digits) is quite literally %w (all alphanumeric characters).

[echasnovski]

Nice job of "translating" Lua patterns into regular English :) As with any regex-like systems, first time encountering them can be daunting. It gets easier with time.

The example was mostly added as a demo of capabilities for what looks like a popular textobject. I personally don't like using it as it feels "too magical". Regular Vim/Neovim operators textobjects together with a_ / i_ from 'mini.ai' feels enough for me. But everyone is different :)