Exclude eruby.yaml from plugin initialization

README.md

@@ -102,6 +102,8 @@ If you set it to an empty list, `[]`, the plugin will not be automatically insta
 
 ### `g:tagalong_additional_filetypes`
 
+Example usage:
+
 ``` vim
 let g:tagalong_additional_filetypes = ['custom', 'another']
 ```
@@ -112,6 +114,22 @@ The plugin should work with any HTML-like tags, so if a compatible filetype is m
 
 Ideally, the above setting would just hold all sensible filetypes, so consider opening a github issue to suggest one that you feel is missing. As long as it's not something too custom, I would likely be okay with adding it to the built-in list.
 
+### `g:tagalong_excluded_filetype_combinations`
+
+Example usage:
+
+``` vim
+let g:tagalong_excluded_filetype_combinations = ['custom.html']
+```
+
+Default value: `['eruby.yaml']`
+
+This setting allows the exclusion of particular filetype dot-combinations from initialization. The "filetypes" setting includes single filetypes, so any combination of them including, for instance, "html" would activate the plugin. So you could set custom filetypes like "html.rails" or something and it would still work.
+
+That said, there are combinations that are not HTML-like. The current default value of the setting, "eruby.yaml" is a good example -- it's being set by vim-rails, but there's no HTML to edit in there.
+
+It's recommended to leave this setting untouched, but you could use it as an escape hatch. If you have any problems with a particular filetype that are solved by an entry in this setting, consider opening an issue to make a change to the defaults.
+
 ### `g:tagalong_mappings`
 
 Example usage:

doc/tagalong.txt

@@ -145,6 +145,27 @@ opening a github issue to suggest one that you feel is missing. As long as
 it's not something too custom, I would likely be okay with adding it to the
 built-in list.
 
+                                     *g:tagalong_excluded_filetype_combinations*
+>
+    let g:tagalong_excluded_filetype_combinations = ['custom.html']
+<
+Default value: ['eruby.yaml']
+
+This setting allows the exclusion of particular filetype dot-combinations from
+initialization. The "filetypes" setting includes single filetypes, so any
+combination of them including, for instance, "html" would activate the plugin.
+So you could set custom filetypes like "html.rails" or something and it would
+still work.
+
+That said, there are combinations that are not HTML-like. The current default
+value of the setting, "eruby.yaml" is a good example -- it's being set by
+vim-rails, but there's no HTML to edit in there.
+
+It's recommended to leave this setting untouched, but you could use it as an
+escape hatch. If you have any problems with a particular filetype that are solved
+by an entry in this setting, consider opening an issue to make a change to the
+defaults.
+
                                                            *g:tagalong_mappings*
 >
     let g:tagalong_mappings = [{'c': '_c'}, 'i', 'a']

plugin/tagalong.vim

@@ -14,6 +14,10 @@ if !exists('g:tagalong_additional_filetypes')
   let g:tagalong_additional_filetypes = []
 endif
 
+if !exists('g:tagalong_excluded_filetype_combinations')
+  let g:tagalong_excluded_filetype_combinations = ['eruby.yaml']
+endif
+
 if !exists('g:tagalong_mappings')
   let g:tagalong_mappings = ['c', 'C', 'v', 'i', 'a']
 endif
@@ -41,9 +45,25 @@ nnoremap <silent> <Plug>TagalongReapply :call tagalong#Reapply()<cr>
 " Needed in order to handle dot-filetypes like "javascript.jsx" or
 " "custom.html".
 function s:InitIfSupportedFiletype(filetype_string)
-  for filetype in split(a:filetype_string, '\.')
-    if index(g:tagalong_filetypes, filetype) >= 0 ||
-          \ index(g:tagalong_additional_filetypes, filetype) >= 0
+  let filetypes = split(a:filetype_string, '\.')
+  call sort(filetypes)
+
+  " first, check for exclusion:
+  for filetype_string in g:tagalong_excluded_filetype_combinations
+    let excluded_filetypes = split(filetype_string, '\.')
+    call sort(excluded_filetypes)
+
+    if filetypes == excluded_filetypes
+      return
+    endif
+  endfor
+
+  " if it's not explicitly excluded, check if it's supported:
+  let included_filetypes = copy(g:tagalong_filetypes)
+  call extend(included_filetypes, g:tagalong_additional_filetypes)
+
+  for filetype in filetypes
+    if index(included_filetypes, filetype) >= 0
       call tagalong#Init()
       return
     endif

spec/plugin/filetype_support_spec.rb

@@ -136,4 +136,24 @@
       HTML
     end
   end
+
+  describe "excluding filetypes" do
+    let(:filename) { 'test.html' }
+
+    specify "allows excluding filetypes with a setting" do
+      vim.command('let g:tagalong_excluded_filetype_combinations = ["html"]')
+
+      set_file_contents <<~HTML
+        <div>Text</div>
+      HTML
+
+      vim.search('div')
+      edit('cwspan')
+
+      # Doesn't work anymore
+      assert_file_contents <<~HTML
+        <span>Text</div>
+      HTML
+    end
+  end
 end

spec/spec_helper.rb

@@ -18,6 +18,11 @@
 RSpec.configure do |config|
   config.include Support::Vim
 
+  config.before :each do
+    # Reset to default plugin settings
+    vim.command('let g:tagalong_excluded_filetype_combinations = ["eruby.yaml"]')
+  end
+
   config.expect_with :rspec do |expectations|
     expectations.include_chain_clauses_in_custom_matcher_descriptions = true
   end