Add option to dynamically disable for a buffer

Based on a GitHub discussion[1], this option lets users specify a
predicate to dynamically enable or disable rainbow delimiters for a
buffer.

[1] https://github.com/HiPhish/rainbow-delimiters.nvim/discussions/130

CHANGELOG.rst

@@ -9,6 +9,16 @@ is based on `Keep a Changelog`_ and this project adheres to `Semantic
 Versioning`_.
 
 
+Unreleased
+##########
+
+Added
+=====
+
+- New option `condition`: allows users to dynamically enable or disable rainbow
+  delimiters for a buffer.
+
+
 [0.5.0] - 2024-07-29
 ####################
 

doc/rainbow-delimiters.txt

@@ -78,6 +78,17 @@ keys are recognized:
   List of Tree-sitter languages for which to disabled rainbow delimiters.
   Rainbow delimiters will be enabled for all other languages.
 
+`condition`
+  Function which receives the current buffer number and returns a boolean; can
+  be used to dynamically decide whether to enable (true) or disable (false)
+  rainbow delimiters for a given buffer.  You could for example use this
+  predicate to disable rainbow delimiters for large files.
+
+  Superceeded by the blacklist, but superceedes the whitelist.  This means if
+  the file type is blacklisted the condtion is ignored, but if the file type
+  is whitelisted or not blacklisted the condition will be evaluated and
+  honoured.
+
 `log`
   Settings for logging information.  This is a dictionary which contains
   further settings.  See |rb-delimiters-logging| for details.

lua/rainbow-delimiters.types.lua

@@ -35,6 +35,8 @@
 ---@field whitelist rainbow_delimiters.language[]?
 ---Blacklist for languages not to highlight
 ---@field blacklist rainbow_delimiters.language[]?
+---Dynamic condition whether to enable rainbow highlighting
+---@field condition (fun(bufnr: number): boolean)?
 ---Logging with log file and log level
 ---@field log rainbow_delimiters.logging?
 

lua/rainbow-delimiters/config.lua

@@ -81,6 +81,13 @@ local M = {
 		end
 
 		return true
+	end,
+	enabled_when = function(bufnr)
+		local conf = vim.g.rainbow_delimiters
+		if not conf or not conf.condition then
+			return true
+		end
+		return conf.condition(bufnr)
 	end
 }
 

plugin/rainbow-delimiters.lua

@@ -58,9 +58,11 @@ create_autocmd('FileType', {
 	group = rb_augroup,
 	callback = function(args)
 		local lang = get_lang(args.match)
+		local bufnr = args.buf
 		if not config.enabled_for(lang) then return end
+		if not config.enabled_when(bufnr) then return end
 
-		lib.attach(args.buf)
+		lib.attach(bufnr)
 	end,
 })
 

test/e2e/selective-activation.lua

@@ -18,14 +18,24 @@ describe('We can disable rainbow delimiters for certain languages', function()
 		end)
 
 		it('Does not run when blacklisted', function()
-			nvim:exec_lua('vim.g.rainbow_delimiters = {strategy = {[""] = the_strategy}, blacklist = {"lua"}}', {})
+			nvim:exec_lua([[
+				vim.g.rainbow_delimiters = {
+					strategy = {[""] = the_strategy},
+					blacklist = {"lua"},
+				}
+			]], {})
 			nvim:command('filetype detect')
 			local attachments = nvim:exec_lua('return the_strategy.attachments[1]', {})
 			assert.is.equal(0, attachments)
 		end)
 
 		it('Runs when whitelisted', function()
-			nvim:exec_lua('vim.g.rainbow_delimiters = {strategy = {[""] = the_strategy}, whitelist = {"lua"}}', {})
+			nvim:exec_lua([[
+				vim.g.rainbow_delimiters = {
+					strategy = {[""] = the_strategy},
+					whitelist = {"lua"},
+				}
+			]], {})
 			nvim:command('filetype detect')
 			local attachments = nvim:exec_lua('return the_strategy.attachments[1]', {})
 			assert.is.equal(1, attachments)
@@ -38,14 +48,100 @@ describe('We can disable rainbow delimiters for certain languages', function()
 		end)
 
 		it('Runs when not blacklisted', function()
-			nvim:exec_lua('vim.g.rainbow_delimiters = {strategy = {[""] = the_strategy}, blacklist = {"lua"}}', {})
+			nvim:exec_lua([[
+				vim.g.rainbow_delimiters = {
+					strategy = {[""] = the_strategy},
+					blacklist = {"lua"},
+				}
+			]], {})
 			nvim:command('filetype detect')
 			local attachments = nvim:exec_lua('return the_strategy.attachments[1]', {})
 			assert.is.equal(1, attachments)
 		end)
 
 		it('Does not run when not whitelisted', function()
-			nvim:exec_lua('vim.g.rainbow_delimiters = {strategy = {[""] = the_strategy}, whitelist = {"lua"}}', {})
+			nvim:exec_lua([[
+				vim.g.rainbow_delimiters = {
+					strategy = {[""] = the_strategy},
+					whitelist = {"lua"}
+				}
+			]], {})
+			nvim:command('filetype detect')
+			local attachments = nvim:exec_lua('return the_strategy.attachments[1]', {})
+			assert.is.equal(0, attachments)
+		end)
+	end)
+
+	describe('For dynamic condition', function()
+		before_each(function()
+			nvim:buf_set_lines(0, 0, -1, true, {'print "Hello world"', '-- vim:ft=lua'})
+		end)
+
+		it('Runs when no condition is set', function()
+			nvim:exec_lua([[
+				vim.g.rainbow_delimiters = {
+					strategy = {[""] = the_strategy},
+					condition = nil,
+				}
+			]], {})
+			nvim:command('filetype detect')
+			local attachments = nvim:exec_lua('return the_strategy.attachments[1]', {})
+			assert.is.equal(1, attachments)
+		end)
+
+		it('Runs when condition is met', function()
+			nvim:exec_lua([[
+				vim.g.rainbow_delimiters = {
+					strategy = {[""] = the_strategy},
+					condition = function(bufnr)
+						return true
+					end,
+				}
+			]], {})
+			nvim:command('filetype detect')
+			local attachments = nvim:exec_lua('return the_strategy.attachments[1]', {})
+			assert.is.equal(1, attachments)
+		end)
+
+		it('Does not run when condition is unmet', function()
+			nvim:exec_lua([[
+				vim.g.rainbow_delimiters = {
+					strategy = {[""] = the_strategy},
+					condition = function(_bufnr)
+						return false
+					end,
+				}
+			]], {})
+			nvim:command('filetype detect')
+			local attachments = nvim:exec_lua('return the_strategy.attachments[1]', {})
+			assert.is.equal(0, attachments)
+		end)
+
+		it('Is ignored for blacklisted buffers', function()
+			nvim:exec_lua([[
+				vim.g.rainbow_delimiters = {
+					strategy = {[""] = the_strategy},
+					blacklist = {'lua'},
+					condition = function(_bufnr)
+						return true
+					end,
+				}
+			]], {})
+			nvim:command('filetype detect')
+			local attachments = nvim:exec_lua('return the_strategy.attachments[1]', {})
+			assert.is.equal(0, attachments)
+		end)
+
+		it('Is takes prededence over the whitelist', function()
+			nvim:exec_lua([[
+				vim.g.rainbow_delimiters = {
+					strategy = {[""] = the_strategy},
+					whitelist = {'lua'},
+					condition = function(_bufnr)
+						return false
+					end,
+				}
+			]], {})
 			nvim:command('filetype detect')
 			local attachments = nvim:exec_lua('return the_strategy.attachments[1]', {})
 			assert.is.equal(0, attachments)