feat: add match_before_cursor field to constant augend

doc/dial.jax

@@ -981,6 +981,10 @@ CONSTANT								*dial-augends-constant*
 		  word = false,
 		  cyclic = true,
 		},
+		augend.constant.new{
+		  elements = {"let", "const"},
+		  match_before_cursor = true,
+		},
 	  },
 	}
 <
@@ -999,6 +1003,10 @@ CONSTANT								*dial-augends-constant*
 		pattern_regexp (string, default: `\C\V\<\(%s\)\>`)
 				文字列検索を行う際の正規表現。 elements に指定した文字列を
 				`%s` に指定します。
+		match_before_cursor (boolean, default: false)
+				true のとき、カーソルが対象の単語より後ろにある場合でもマッチ
+				します。ただし、カーソル上またはカーソルの後に他の有効な被加数が
+				存在すればそちらが優先されます。
 
 注意: `&&` と `||` のように、記号からなる文字列を相互変換するときは `cyclic`
 を false にしてください。

doc/dial.txt

@@ -1014,6 +1014,10 @@ Predefined sequence of strings. You can use this rule with
 		  word = false,
 		  cyclic = true,
 		},
+		augend.constant.new{
+		  elements = {"let", "const"},
+		  match_before_cursor = true,
+		},
 	  },
 	}
 <
@@ -1033,6 +1037,10 @@ The argument table of `augend.constant.new` can take the following keys:
 		pattern_regexp (string, default: `\C\V\<\(%s\)\>`)
 				A regular expression used in search. `%s` represents the string
 				specified in `elements.`
+		match_before_cursor (boolean, default: false)
+				If true, it matches even when the cursor is positioned after
+				the target word. In that case, however, any other valid augend
+				on or after the cursor will take precedence.
 
 NOTE: Set `cyclic` to false when cross-converting strings consisting of
 symbols, such as `&&` and `||`.

lua/dial/augend/common.lua

@@ -6,12 +6,14 @@ local M = {}
 
 ---augend の find field を簡単に実装する。
 ---@param ptn string
+---@param allow_match_before_cursor? boolean
 ---@return findf
-function M.find_pattern(ptn)
+function M.find_pattern(ptn, allow_match_before_cursor)
     ---@param line string
     ---@param cursor? integer
     ---@return textrange?
     local function f(line, cursor)
+        local match_before_cursor = nil
         local idx_start = 1
         while idx_start <= #line do
             local s, e = line:find(ptn, idx_start)
@@ -21,6 +23,7 @@ function M.find_pattern(ptn)
                     -- cursor が終了文字より後ろにあったら終了
                     return { from = s, to = e }
                 else
+                    match_before_cursor = { from = s, to = e }
                     -- 終了文字の後ろから探し始める
                     idx_start = e + 1
                 end
@@ -29,19 +32,24 @@ function M.find_pattern(ptn)
                 break
             end
         end
+        if allow_match_before_cursor then
+            return match_before_cursor
+        end
         return nil
     end
     return f
 end
 
 -- augend の find field を簡単に実装する。
 ---@param ptn string
+---@param allow_match_before_cursor? boolean
 ---@return findf
-function M.find_pattern_regex(ptn)
+function M.find_pattern_regex(ptn, allow_match_before_cursor)
     ---@param line string
     ---@param cursor? integer
     ---@return textrange?
     local function f(line, cursor)
+        local match_before_cursor = nil
         local idx_start = 1
         while idx_start <= #line do
             local s, e = vim.regex(ptn):match_str(line:sub(idx_start))
@@ -55,6 +63,7 @@ function M.find_pattern_regex(ptn)
                     -- cursor が終了文字より後ろにあったら終了
                     return { from = s, to = e }
                 else
+                    match_before_cursor = { from = s, to = e }
                     -- 終了文字の後ろから探し始める
                     idx_start = e + 1
                 end
@@ -63,6 +72,9 @@ function M.find_pattern_regex(ptn)
                 break
             end
         end
+        if allow_match_before_cursor then
+            return match_before_cursor
+        end
         return nil
     end
     return f

lua/dial/augend/constant.lua

@@ -1,7 +1,7 @@
 local util = require "dial.util"
 local common = require "dial.augend.common"
 
----@alias AugendConstantConfig { elements: string[], cyclic: boolean, pattern_regexp: string, preserve_case: boolean }
+---@alias AugendConstantConfig { elements: string[], cyclic: boolean, pattern_regexp: string, preserve_case: boolean, match_before_cursor: boolean }
 
 ---@class AugendConstant
 ---@implement Augend
@@ -33,7 +33,7 @@ local function preserve_case(word)
     return nil
 end
 
----@param config { elements: string[], word?: boolean, cyclic?: boolean, pattern_regexp?: string, preserve_case?: boolean }
+---@param config { elements: string[], word?: boolean, cyclic?: boolean, pattern_regexp?: string, preserve_case?: boolean, match_before_cursor?: boolean }
 ---@return Augend
 function M.new(config)
     util.validate_list("config.elements", config.elements, "string")
@@ -43,10 +43,14 @@ function M.new(config)
         cyclic = { config.cyclic, "boolean", true },
         pattern_regexp = { config.pattern_regexp, "string", true },
         preserve_case = { config.preserve_case, "boolean", true },
+        match_before_cursor = { config.match_before_cursor, "boolean", true },
     }
     if config.preserve_case == nil then
         config.preserve_case = false
     end
+    if config.match_before_cursor == nil then
+        config.match_before_cursor = false
+    end
     if config.pattern_regexp == nil then
         local case_sensitive_flag = util.if_expr(config.preserve_case, [[\c]], [[\C]])
         local word = util.unwrap_or(config.word, true)
@@ -70,7 +74,7 @@ function AugendConstant:find(line, cursor)
         return vim.fn.escape(e, [[/\]])
     end, self.config.elements)
     local vim_regex_ptn = self.config.pattern_regexp:format(table.concat(escaped_elements, [[\|]]))
-    return common.find_pattern_regex(vim_regex_ptn)(line, cursor)
+    return common.find_pattern_regex(vim_regex_ptn, self.config.match_before_cursor)(line, cursor)
 end
 
 ---@param text string

tests/dial/augend/constant_spec.lua

@@ -2,4 +2,25 @@ local constant = require("dial.augend").constant
 
 describe("Test of constant between two words", function()
     local augend = constant.new { elements = { "true", "false" } }
+
+    describe("find function", function()
+        it("can find a completely matching word", function()
+            assert.are.same(augend:find("enable = true", 1), { from = 10, to = 13 })
+            assert.are.same(augend:find("enable = false", 1), { from = 10, to = 14 })
+        end)
+        it("does not find a word including element words", function()
+            assert.are.same(augend:find("mistakenly construed", 1), nil)
+        end)
+        it("does not find a word before the cursor when match_before_cursor = false", function()
+            assert.are.same(augend:find("true negative", 5), nil)
+        end)
+    end)
+
+    augend = constant.new { elements = { "true", "false" }, match_before_cursor = true }
+
+    describe("find function", function()
+        it("does find a word before the cursor when match_before_cursor = true", function()
+            assert.are.same(augend:find("true positive", 5), { from = 1, to = 4 })
+        end)
+    end)
 end)