all: support overriding individual function from .v files in .c.v or .js.v files.

vlib/v/ast/ast.v

@@ -388,7 +388,8 @@ pub:
 	method_idx      int
 	rec_mut         bool // is receiver mutable
 	rec_share       ShareType
-	language        Language
+	language        Language       // V, C, JS
+	file_mode       Language       // whether *the file*, where a function was a '.c.v', '.js.v' etc.
 	no_body         bool           // just a definition `fn C.malloc()`
 	is_builtin      bool           // this function is defined in builtin/strconv
 	body_pos        token.Position // function bodys position

vlib/v/ast/table.v

@@ -87,6 +87,7 @@ pub:
 	is_keep_alive   bool // passed memory must not be freed (by GC) before function returns
 	no_body         bool // a pure declaration like `fn abc(x int)`; used in .vh files, C./JS. fns.
 	mod             string
+	file_mode       Language
 	pos             token.Position
 	return_type_pos token.Position
 pub mut:

vlib/v/parser/fn.v

@@ -364,6 +364,7 @@ fn (mut p Parser) fn_decl() ast.FnDecl {
 		&& (p.file_base.ends_with('_test.v')
 		|| p.file_base.all_before_last('.v').all_before_last('.').ends_with('_test'))
 
+	file_mode := p.file_backend_mode
 	// Register
 	if is_method {
 		mut type_sym := p.table.get_type_symbol(rec.typ)
@@ -386,6 +387,7 @@ fn (mut p Parser) fn_decl() ast.FnDecl {
 		}
 		type_sym_method_idx = type_sym.register_method(ast.Fn{
 			name: name
+			file_mode: file_mode
 			params: params
 			return_type: return_type
 			is_variadic: is_variadic
@@ -412,11 +414,21 @@ fn (mut p Parser) fn_decl() ast.FnDecl {
 		} else {
 			name = p.prepend_mod(name)
 		}
-		if !p.pref.translated && language == .v && name in p.table.fns {
+		if !p.pref.translated && language == .v {
+			if existing := p.table.fns[name] {
+				if existing.name != '' {
+					if file_mode == .v && existing.file_mode != .v {
+						// a definition made in a .c.v file, should have a priority over a .v file definition of the same function
+						name = p.prepend_mod('pure_v_but_overriden_by_${existing.file_mode}_$short_fn_name')
+					} else {
 						p.table.redefined_fns << name
 					}
+				}
+			}
+		}
 		p.table.register_fn(ast.Fn{
 			name: name
+			file_mode: file_mode
 			params: params
 			return_type: return_type
 			is_variadic: is_variadic

vlib/v/tests/project_with_c_code_3/.gitignore

@@ -0,0 +1,3 @@
+main
+mod1/c/implementation.o
+main_test

vlib/v/tests/project_with_c_code_3/.v.mod.stop

@@ -0,0 +1,4 @@
+Do not delete this file.
+It is used by V to stop the lookup for v.mod,
+so that the top level vlib/v.mod is not found,
+if you delete mod1/v.mod .

vlib/v/tests/project_with_c_code_3/main.v

@@ -0,0 +1,15 @@
+module main
+
+import v.tests.project_with_c_code_3.mod1
+
+fn main() {
+	res := mod1.vadd(1, 2)
+	println('mod1.vadd(1, 2): ' + res.str())
+	$if js {
+		assert res == 2003
+	} $else {
+		assert res == 1003
+	}
+	println('mod1.a_common_pure_v_fn(): ' + mod1.a_common_pure_v_fn().str())
+	assert mod1.a_common_pure_v_fn() == 987654
+}

vlib/v/tests/project_with_c_code_3/main_test.v

@@ -0,0 +1,13 @@
+import v.tests.project_with_c_code_3.mod1
+
+fn test_using_c_code_in_the_same_module_works() {
+	$if js {
+		assert 2003 == mod1.vadd(1, 2)
+	} $else {
+		assert 1003 == mod1.vadd(1, 2)
+	}
+}
+
+fn test_a_common_pure_v_fn_works() {
+	assert mod1.a_common_pure_v_fn() == 987654
+}

vlib/v/tests/project_with_c_code_3/mod1/v.mod

@@ -0,0 +1,5 @@
+Module {
+	name: 'mod1',
+	description: 'A simple module, containing C code.',
+	dependencies: []
+}

vlib/v/tests/project_with_c_code_3/mod1/wrapper.c.v

@@ -0,0 +1,5 @@
+module mod1
+
+pub fn vadd(a int, b int) int {
+	return 1003
+}

vlib/v/tests/project_with_c_code_3/mod1/wrapper.js.v

@@ -0,0 +1,6 @@
+module mod1
+
+// NB: the function here, overrides the one from wrapper.v
+pub fn vadd(a int, b int) int {
+	return 2003
+}

vlib/v/tests/project_with_c_code_3/mod1/wrapper.v

@@ -0,0 +1,11 @@
+module mod1
+
+// NB: the function here, should be overriden by the one in the wrapper.c.v file with the same name
+pub fn vadd(a int, b int) int {
+	return 123456
+}
+
+// this should NOT be overriden by the different wrapper.X.v files:
+pub fn a_common_pure_v_fn() int {
+	return 987654
+}