fix return value of os.writefile_ifnotequal()

src/host/os_writefile_ifnotequal.c

@@ -105,7 +105,7 @@ int os_writefile_ifnotequal(lua_State* L)
 
 		if (!error)
 		{
-			lua_pushinteger(L, error ? -1 : 0);
+			lua_pushinteger(L, 1);
 			return 1;
 		}
 	}

tests/base/test_os.lua

@@ -542,6 +542,18 @@
 -- Helpers
 --
 
+	-- Save the real functions before test runner installs its stubs.
+	local real_writefile_ifnotequal = os.writefile_ifnotequal
+	local real_io_open = io.open
+
+	local function real_readfile(filepath)
+		local f = real_io_open(filepath, "rb")
+		if not f then return nil end
+		local content = f:read("*a")
+		f:close()
+		return content
+	end
+
 	local tmpname = function()
 		local p = os.tmpname()
         if p:startswith("\\") then
@@ -568,6 +580,52 @@
 	end
 
 
+--
+-- os.writefile_ifnotequal() tests.
+--
+
+	function suite.writefile_ifnotequal_WritesNewFile()
+		local filepath = tmpname()
+		local content = "Hello, World!"
+		local ok, err = real_writefile_ifnotequal(content, filepath)
+		test.isequal(1, ok)
+		test.isnil(err)
+		test.istrue(os.isfile(filepath))
+		test.isequal(content, real_readfile(filepath))
+		os.remove(filepath)
+	end
+
+	function suite.writefile_ifnotequal_SkipsIdenticalContent()
+		local filepath = tmpname()
+		local content = "Identical content"
+		-- Write the file first
+		local ok1, err1 = real_writefile_ifnotequal(content, filepath)
+		test.isequal(1, ok1)
+		test.isnil(err1)
+		-- Try to write identical content
+		local ok2, err2 = real_writefile_ifnotequal(content, filepath)
+		test.isequal(0, ok2)
+		test.isnil(err2)
+		test.isequal(content, real_readfile(filepath))
+		os.remove(filepath)
+	end
+
+	function suite.writefile_ifnotequal_UpdatesWhenContentDiffers()
+		local filepath = tmpname()
+		local content1 = "First content"
+		local content2 = "Second content"
+		-- Write the file first
+		local ok1, err1 = real_writefile_ifnotequal(content1, filepath)
+		test.isequal(1, ok1)
+		test.isnil(err1)
+		-- Write different content
+		local ok2, err2 = real_writefile_ifnotequal(content2, filepath)
+		test.isequal(1, ok2)
+		test.isnil(err2)
+		test.isequal(content2, real_readfile(filepath))
+		os.remove(filepath)
+	end
+
 --
 -- os.remove() tests.
 --

website/docs/os/os.writefile_ifnotequal.md

@@ -13,7 +13,7 @@ ok, err = os.writefile_ifnotequal("text", "filename")
 
 ### Return Value ###
 
-True if successful, otherwise nil and an error message.
+`1` if successful, `0` if the string is identical to the current file contents, otherwise `-1` and an error message.
 
 
 ### Availability ###