From 5518bfc7d5534e061bef8fdb3fef4e0280bae558 Mon Sep 17 00:00:00 2001
From: Alexander Medvednikov <alexander@medvednikov.com>
Date: Wed, 22 Apr 2026 13:58:49 +0300
Subject: [PATCH] all: remove src/ virtual dirs (replaced with v.mod subdirs)

---
 vlib/v/builder/builder.v                      | 85 ++++++++++++-------
 vlib/v/builder/builder_test.v                 | 54 +-----------
 vlib/v/builder/compile.v                      | 21 +----
 vlib/v/gen/c/cgen.v                           | 10 ++-
 .../tests/projects_that_should_compile_test.v | 20 ++---
 .../module_named_cache/src/cache/my_cache.v   |  3 -
 .../testdata/module_named_cache/src/main.v    |  8 --
 .../v/tests/testdata/module_named_cache/v.mod |  7 --
 .../modules/somemoduletwo/somemoduletwo.v     |  7 --
 .../tests/testdata/modules_in_src/src/main.v  |  8 --
 .../src/modules/somemodule/somemodule.v       |  7 --
 vlib/v/tests/testdata/modules_in_src/v.mod    |  7 --
 .../testdata/sibling_modules_in_src/src/a/a.v |  5 --
 .../testdata/sibling_modules_in_src/src/b/b.v |  7 --
 .../sibling_modules_in_src/src/main.v         |  7 --
 .../testdata/sibling_modules_in_src/v.mod     |  3 -
 vlib/v/util/module.v                          | 63 ++++----------
 vlib/v/vmod/vmod.v                            |  5 +-
 18 files changed, 94 insertions(+), 233 deletions(-)
 delete mode 100644 vlib/v/tests/testdata/module_named_cache/src/cache/my_cache.v
 delete mode 100644 vlib/v/tests/testdata/module_named_cache/src/main.v
 delete mode 100644 vlib/v/tests/testdata/module_named_cache/v.mod
 delete mode 100644 vlib/v/tests/testdata/modules_in_src/modules/somemoduletwo/somemoduletwo.v
 delete mode 100644 vlib/v/tests/testdata/modules_in_src/src/main.v
 delete mode 100644 vlib/v/tests/testdata/modules_in_src/src/modules/somemodule/somemodule.v
 delete mode 100644 vlib/v/tests/testdata/modules_in_src/v.mod
 delete mode 100644 vlib/v/tests/testdata/sibling_modules_in_src/src/a/a.v
 delete mode 100644 vlib/v/tests/testdata/sibling_modules_in_src/src/b/b.v
 delete mode 100644 vlib/v/tests/testdata/sibling_modules_in_src/src/main.v
 delete mode 100644 vlib/v/tests/testdata/sibling_modules_in_src/v.mod

diff --git a/vlib/v/builder/builder.v b/vlib/v/builder/builder.v
index 962a70244..04e6fdc97 100644
--- a/vlib/v/builder/builder.v
+++ b/vlib/v/builder/builder.v
@@ -574,20 +574,46 @@ pub fn (b &Builder) v_files_from_dir(dir string) []string {
 	}
 	mut res := b.pref.should_compile_filtered_files(dir, files)
 	if res.len == 0 {
-		// Perhaps the .v files are stored in a custom source root?
-		source_root := source_root_from_vmod_root(dir) or { os.join_path(dir, 'src') }
-		if source_root != dir && os.is_dir(source_root) {
-			if b.pref.is_verbose {
-				println('v_files_from_dir ("${source_root}") (v.mod source root)')
+		// An explicit `base_url` in v.mod still re-homes the source folder.
+		if source_root := source_root_from_vmod_root(dir) {
+			if source_root != dir && os.is_dir(source_root) {
+				if b.pref.is_verbose {
+					println('v_files_from_dir ("${source_root}") (v.mod base_url)')
+				}
+				files = os.ls(source_root) or { panic(err) }
+				source_dir = os.real_path(source_root)
+				res = b.pref.should_compile_filtered_files(source_root, files)
 			}
-			files = os.ls(source_root) or { panic(err) }
-			source_dir = os.real_path(source_root)
-			res = b.pref.should_compile_filtered_files(source_root, files)
+		}
+		if res.len == 0 {
+			report_removed_src_layout_if_any(dir)
 		}
 	}
 	return b.with_same_module_subdir_files(source_dir, res)
 }
 
+// report_removed_src_layout_if_any prints a clear error if `dir` still relies on
+// the removed virtual `src/` module layout (sources under `dir/src/` instead of
+// at the module root). The explicit `base_url` opt-in in v.mod is unaffected.
+fn report_removed_src_layout_if_any(dir string) {
+	src_dir := os.join_path(dir, 'src')
+	if !os.is_dir(src_dir) {
+		return
+	}
+	src_files := os.ls(src_dir) or { return }
+	mut has_v_files := false
+	for f in src_files {
+		if f.ends_with('.v') {
+			has_v_files = true
+			break
+		}
+	}
+	if !has_v_files {
+		return
+	}
+	verror('the virtual `src/` module directory is no longer supported.\nV found .v source files under ${src_dir}, but will not treat `src/` as a virtual module root anymore.\nPlease move the sources up from `src/` into ${dir}:\n\tmv ${src_dir}/*.v ${dir}/\n\trmdir ${src_dir}\n\nIf you really want the sources to live in a subfolder, set `base_url` in v.mod to point at it.')
+}
+
 fn (b &Builder) with_same_module_subdir_files(source_dir string, v_files []string) []string {
 	mut mcache := vmod.get_cache()
 	vmod_file_location := mcache.get_by_folder(source_dir)
@@ -609,9 +635,7 @@ fn (b &Builder) with_same_module_subdir_files(source_dir string, v_files []strin
 		seen[os.real_path(file)] = true
 	}
 	for subdir in subdirs {
-		normalized_subdir := normalize_same_module_subdir(subdir, module_source_root) or {
-			continue
-		}
+		normalized_subdir := normalize_same_module_subdir(subdir, manifest.base_url) or { continue }
 		subdir_path := os.join_path(module_source_root, normalized_subdir)
 		b.collect_same_module_v_files(vmod_file_location.vmod_folder, subdir_path, mut seen, mut
 			res)
@@ -621,29 +645,30 @@ fn (b &Builder) with_same_module_subdir_files(source_dir string, v_files []strin
 
 fn (b &Builder) module_source_root(module_root string) string {
 	real_module_root := os.real_path(module_root)
-	files := os.ls(real_module_root) or { return real_module_root }
-	if b.pref.should_compile_filtered_files(real_module_root, files).len == 0 {
-		src_path := os.join_path(real_module_root, 'src')
-		if os.is_dir(src_path) {
-			return os.real_path(src_path)
+	if source_root := source_root_from_vmod_root(real_module_root) {
+		if source_root != real_module_root && os.is_dir(source_root) {
+			return os.real_path(source_root)
 		}
 	}
 	return real_module_root
 }
 
-fn normalize_same_module_subdir(subdir string, module_source_root string) !string {
+fn normalize_same_module_subdir(subdir string, base_url string) !string {
 	mut normalized := os.norm_path(subdir.trim_space().replace('\\', os.path_separator).replace('/',
 		os.path_separator))
 	if normalized == '' || normalized == '.' || os.is_abs_path(normalized) {
 		return error('invalid subdir')
 	}
-	if os.base(module_source_root) == 'src' {
-		src_prefix := 'src' + os.path_separator
-		if normalized == 'src' {
-			return error('invalid subdir')
-		}
-		if normalized.starts_with(src_prefix) {
-			normalized = normalized.all_after(src_prefix)
+	if base_url != '' {
+		base := os.norm_path(base_url).trim_left(os.path_separator).trim_right(os.path_separator)
+		if base != '' {
+			base_prefix := base + os.path_separator
+			if normalized == base {
+				return error('invalid subdir')
+			}
+			if normalized.starts_with(base_prefix) {
+				normalized = normalized.all_after(base_prefix)
+			}
 		}
 	}
 	normalized = normalized.trim_left(os.path_separator).trim_right(os.path_separator)
@@ -710,15 +735,17 @@ fn manifest_from_vmod_root(vmod_root string) !vmod.Manifest {
 
 fn source_root_from_vmod_root(vmod_root string) !string {
 	manifest := manifest_from_vmod_root(vmod_root)!
+	if manifest.base_url == '' {
+		return error('module not found')
+	}
 	return manifest.source_root(vmod_root)
 }
 
-fn lookup_source_root_from_vmod_root(vmod_root string) string {
-	return source_root_from_vmod_root(vmod_root) or { os.join_path(vmod_root, 'src') }
-}
-
 fn find_module_path_from_vmod_root(vmod_root string, mod string) !string {
 	manifest := manifest_from_vmod_root(vmod_root)!
+	if manifest.base_url == '' {
+		return error('module not found')
+	}
 	tail_path := mod_tail_after_vmod_name(mod, manifest.name) or {
 		return error('module not found')
 	}
@@ -747,8 +774,8 @@ fn find_module_path_from_search_root(search_path string, mod string) !string {
 		if !os.is_file(os.join_path(candidate_root, 'v.mod')) {
 			continue
 		}
+		source_root := source_root_from_vmod_root(candidate_root) or { continue }
 		submodule_path := mod_parts[i..].join(os.path_separator)
-		source_root := lookup_source_root_from_vmod_root(candidate_root)
 		src_try_path := os.join_path(source_root, submodule_path)
 		if os.is_dir(src_try_path) {
 			return src_try_path
diff --git a/vlib/v/builder/builder_test.v b/vlib/v/builder/builder_test.v
index 008985212..a814ba4f8 100644
--- a/vlib/v/builder/builder_test.v
+++ b/vlib/v/builder/builder_test.v
@@ -25,8 +25,7 @@ fn run_v_ok(command string) string {
 
 fn test_conditional_executable_removal() {
 	os.chdir(test_path)!
-	os.mkdir_all('src')!
-	os.write_file('src/main.v', 'fn main(){\n\tprintln("Hello World!")\n}\n')!
+	os.write_file('main.v', 'fn main(){\n\tprintln("Hello World!")\n}\n')!
 
 	mut executable := 'run_check'
 	$if windows {
@@ -93,57 +92,6 @@ pub struct BS{}
 	assert os.execute('./${executable}').output.trim_space() == 'AS{}=>BS{}'
 }
 
-fn test_run_explicit_src_directory_uses_project_root_lookup() {
-	os.chdir(test_path)!
-	project_dir := os.join_path(test_path, 'run_src_project')
-	defer {
-		os.chdir(test_path) or {}
-	}
-	os.mkdir_all(os.join_path(project_dir, 'src'))!
-	os.mkdir_all(os.join_path(project_dir, 'modules', 'somemoduletwo'))!
-	os.write_file(os.join_path(project_dir, 'src', 'main.v'), 'module main
-import somemoduletwo
-
-fn main() {
-	println(somemoduletwo.name())
-}
-')!
-	os.write_file(os.join_path(project_dir, 'modules', 'somemoduletwo', 'somemoduletwo.v'), 'module somemoduletwo
-
-pub fn name() string {
-	return "somemoduletwo"
-}
-')!
-	os.chdir(project_dir)!
-	assert run_v_ok('${os.quoted_path(vexe)} run src').trim_space() == 'somemoduletwo'
-	assert run_v_ok('${os.quoted_path(vexe)} run ./src').trim_space() == 'somemoduletwo'
-}
-
-fn test_run_explicit_main_file_inside_src_resolves_nested_module_imports() {
-	os.chdir(test_path)!
-	project_dir := os.join_path(test_path, 'run_src_main_file_project')
-	os.mkdir_all(os.join_path(project_dir, 'src', 'infrastructure', 'database'))!
-	os.write_file(os.join_path(project_dir, 'src', 'infrastructure', 'database', 'database.v'), 'module database
-
-pub fn name() string {
-	return "database"
-}
-')!
-	os.write_file(os.join_path(project_dir, 'src', 'infrastructure', 'infrastructure.v'), 'module infrastructure
-')!
-	os.write_file(os.join_path(project_dir, 'src', 'main.v'), 'module main
-
-import infrastructure.database
-
-fn main() {
-	println(database.name())
-}
-')!
-
-	main_file := os.join_path('run_src_main_file_project', 'src', 'main.v')
-	assert run_v_ok('${os.quoted_path(vexe)} run ${os.quoted_path(main_file)}').trim_space() == 'database'
-}
-
 fn test_run_custom_base_url_uses_project_root_lookup() {
 	os.chdir(test_path)!
 	project_dir := os.join_path(test_path, 'run_base_url_project')
diff --git a/vlib/v/builder/compile.v b/vlib/v/builder/compile.v
index 3fda0a6e5..8e587187c 100644
--- a/vlib/v/builder/compile.v
+++ b/vlib/v/builder/compile.v
@@ -246,9 +246,6 @@ pub fn (mut v Builder) set_module_lookup_paths() {
 		println('x: "${x}"')
 	}
 
-	if os.exists(os.join_path(lookup_root, 'src/modules')) {
-		v.module_search_paths << os.join_path(lookup_root, 'src/modules')
-	}
 	if source_root := source_root_from_vmod_root(lookup_root) {
 		source_modules := os.join_path(source_root, 'modules')
 		if source_modules !in v.module_search_paths && os.exists(source_modules) {
@@ -267,6 +264,8 @@ pub fn (mut v Builder) set_module_lookup_paths() {
 }
 
 fn (v &Builder) module_lookup_root() string {
+	// If `compiled_dir` is the base_url-configured source folder, treat the
+	// enclosing module folder as the lookup root so sibling `modules/` resolves.
 	mut mcache := vmod.get_cache()
 	vmod_file_location := mcache.get_by_folder(v.compiled_dir)
 	if vmod_file_location.vmod_file != '' && vmod_file_location.vmod_folder != v.compiled_dir {
@@ -276,22 +275,6 @@ fn (v &Builder) module_lookup_root() string {
 			}
 		}
 	}
-	if os.file_name(v.compiled_dir) != 'src' {
-		return v.compiled_dir
-	}
-	project_dir := os.dir(v.compiled_dir)
-	if project_dir == v.compiled_dir {
-		return v.compiled_dir
-	}
-	if vmod_file_location.vmod_folder == project_dir {
-		return project_dir
-	}
-	if os.real_path(os.getwd()) == project_dir {
-		return project_dir
-	}
-	if os.is_dir(os.join_path(project_dir, 'modules')) {
-		return project_dir
-	}
 	return v.compiled_dir
 }
 
diff --git a/vlib/v/gen/c/cgen.v b/vlib/v/gen/c/cgen.v
index cbd509b40..31e6624f6 100644
--- a/vlib/v/gen/c/cgen.v
+++ b/vlib/v/gen/c/cgen.v
@@ -6583,8 +6583,14 @@ fn (mut g Gen) selector_expr(node ast.SelectorExpr) {
 						if field_sym.kind == .interface && cast_sym.kind == .interface
 							&& !is_option_unwrap {
 							ptr := '*'.repeat(field.typ.nr_muls())
-							dot := if node.expr_type.is_ptr() { '->' } else { '.' }
-							g.write('I_${field_sym.cname}_as_I_${cast_sym.cname}(${ptr}${node.expr}${dot}${node.field_name}))')
+							// Emit the receiver via g.expr() so smartcasts on the
+							// receiver (e.g. `mut child is SubWindow` → `(child._SubWindow)`)
+							// are preserved. Use lhs_expr_type for the dot since it
+							// reflects the smartcast'd type, not the original interface.
+							g.write('I_${field_sym.cname}_as_I_${cast_sym.cname}(${ptr}')
+							g.expr(node.expr)
+							dot := if lhs_expr_type.is_ptr() { '->' } else { '.' }
+							g.write('${dot}${node.field_name}))')
 							return
 						} else if !is_option_unwrap {
 							if i != 0 {
diff --git a/vlib/v/tests/projects_that_should_compile_test.v b/vlib/v/tests/projects_that_should_compile_test.v
index 4b2a00555..1f920cc23 100644
--- a/vlib/v/tests/projects_that_should_compile_test.v
+++ b/vlib/v/tests/projects_that_should_compile_test.v
@@ -32,16 +32,16 @@ fn setup_module_resolution_workdir_fixture() string {
 		'v_module_resolution_independent_of_workdir_${os.getpid()}')
 	interp := r'${'
 	os.rmdir_all(workspace) or {}
-	os.mkdir_all(os.join_path(workspace, 'app', 'src')) or { panic(err) }
-	os.mkdir_all(os.join_path(workspace, 'lib', 'src')) or { panic(err) }
+	os.mkdir_all(os.join_path(workspace, 'app')) or { panic(err) }
+	os.mkdir_all(os.join_path(workspace, 'lib')) or { panic(err) }
 	write_file(os.join_path(workspace, '.v.mod.stop'), '')
 	write_file(os.join_path(workspace, 'app', 'v.mod'),
 		"Module {\n\tname: 'app'\n\tdescription: ''\n\tversion: ''\n\tlicense: ''\n\tdependencies: []\n}\n")
-	write_file(os.join_path(workspace, 'app', 'src', 'main.v'),
+	write_file(os.join_path(workspace, 'app', 'main.v'),
 		"module main\n\nimport lib\n\nfn main() {\n\tprintln('Hello ${interp}lib.square(4)}!')\n}\n")
 	write_file(os.join_path(workspace, 'lib', 'v.mod'),
 		"Module {\n\tname: 'lib'\n\tdescription: ''\n\tversion: ''\n\tlicense: ''\n\tdependencies: []\n}\n")
-	write_file(os.join_path(workspace, 'lib', 'src', 'lib.v'),
+	write_file(os.join_path(workspace, 'lib', 'lib.v'),
 		'module lib\n\npub fn square(x int) int {\n\treturn x * x\n}\n')
 	return workspace
 }
@@ -63,12 +63,6 @@ fn test_projects_should_run() {
 	}
 	res := vrun_ok('run', vroot_path('vlib/v/tests/testdata/enum_in_builtin') + os.path_separator)
 	assert res.trim_space() == 'v0'
-
-	res2 := vrun_ok('run', vroot_path('vlib/v/tests/testdata/modules_in_src/'))
-	assert res2.trim_space() == 'somemodule somemoduletwo'
-
-	res3 := vrun_ok('run', vroot_path('vlib/v/tests/testdata/module_named_cache/'))
-	assert res3.trim_space().ends_with('cache.a: 123')
 }
 
 fn test_running_subdir_project_with_parent_vmod_works() {
@@ -99,14 +93,14 @@ fn test_running_module_with_same_module_subdirs_setting_works() {
 	defer {
 		os.rmdir_all(root) or {}
 	}
-	os.mkdir_all(os.join_path(root, 'app', 'foo', 'src', 'internal', 'nested'))!
+	os.mkdir_all(os.join_path(root, 'app', 'foo', 'internal', 'nested'))!
 	os.write_file(os.join_path(root, 'app', 'main.v'),
 		'module main\n\nimport foo\n\nfn main() {\n\tprintln(foo.answer())\n}\n')!
 	os.write_file(os.join_path(root, 'app', 'foo', 'v.mod'),
 		"Module {\n\tname: 'foo'\n\tsubdirs: ['internal']\n}\n")!
-	os.write_file(os.join_path(root, 'app', 'foo', 'src', 'foo.v'),
+	os.write_file(os.join_path(root, 'app', 'foo', 'foo.v'),
 		'module foo\n\npub fn answer() int {\n\treturn secret()\n}\n')!
-	os.write_file(os.join_path(root, 'app', 'foo', 'src', 'internal', 'nested', 'secret.v'),
+	os.write_file(os.join_path(root, 'app', 'foo', 'internal', 'nested', 'secret.v'),
 		'module foo\n\nfn secret() int {\n\treturn 42\n}\n')!
 	old_dir := os.getwd()
 	defer {
diff --git a/vlib/v/tests/testdata/module_named_cache/src/cache/my_cache.v b/vlib/v/tests/testdata/module_named_cache/src/cache/my_cache.v
deleted file mode 100644
index ff345da98..000000000
--- a/vlib/v/tests/testdata/module_named_cache/src/cache/my_cache.v
+++ /dev/null
@@ -1,3 +0,0 @@
-module cache
-
-pub const a = 123
diff --git a/vlib/v/tests/testdata/module_named_cache/src/main.v b/vlib/v/tests/testdata/module_named_cache/src/main.v
deleted file mode 100644
index 2c476aa1e..000000000
--- a/vlib/v/tests/testdata/module_named_cache/src/main.v
+++ /dev/null
@@ -1,8 +0,0 @@
-module main
-
-import cache
-
-fn main() {
-	println('Hello World!')
-	dump(cache.a)
-}
diff --git a/vlib/v/tests/testdata/module_named_cache/v.mod b/vlib/v/tests/testdata/module_named_cache/v.mod
deleted file mode 100644
index 7dd2a885c..000000000
--- a/vlib/v/tests/testdata/module_named_cache/v.mod
+++ /dev/null
@@ -1,7 +0,0 @@
-Module {
-	name: 'aa'
-	description: 'AA'
-	version: '0.0.0'
-	license: 'MIT'
-	dependencies: []
-}
diff --git a/vlib/v/tests/testdata/modules_in_src/modules/somemoduletwo/somemoduletwo.v b/vlib/v/tests/testdata/modules_in_src/modules/somemoduletwo/somemoduletwo.v
deleted file mode 100644
index 457675ebc..000000000
--- a/vlib/v/tests/testdata/modules_in_src/modules/somemoduletwo/somemoduletwo.v
+++ /dev/null
@@ -1,7 +0,0 @@
-module somemoduletwo
-
-const name = 'somemoduletwo'
-
-pub fn name() string {
-	return name
-}
diff --git a/vlib/v/tests/testdata/modules_in_src/src/main.v b/vlib/v/tests/testdata/modules_in_src/src/main.v
deleted file mode 100644
index 0c246529a..000000000
--- a/vlib/v/tests/testdata/modules_in_src/src/main.v
+++ /dev/null
@@ -1,8 +0,0 @@
-module main
-
-import somemodule
-import somemoduletwo
-
-fn main() {
-	println('${somemodule.name()} ${somemoduletwo.name()}')
-}
diff --git a/vlib/v/tests/testdata/modules_in_src/src/modules/somemodule/somemodule.v b/vlib/v/tests/testdata/modules_in_src/src/modules/somemodule/somemodule.v
deleted file mode 100644
index e4c843856..000000000
--- a/vlib/v/tests/testdata/modules_in_src/src/modules/somemodule/somemodule.v
+++ /dev/null
@@ -1,7 +0,0 @@
-module somemodule
-
-const name = 'somemodule'
-
-pub fn name() string {
-	return name
-}
diff --git a/vlib/v/tests/testdata/modules_in_src/v.mod b/vlib/v/tests/testdata/modules_in_src/v.mod
deleted file mode 100644
index dc334bd0e..000000000
--- a/vlib/v/tests/testdata/modules_in_src/v.mod
+++ /dev/null
@@ -1,7 +0,0 @@
-Module {
-	name: 'somemodule'
-	description: ''
-	version: ''
-	license: ''
-	dependencies: []
-}
diff --git a/vlib/v/tests/testdata/sibling_modules_in_src/src/a/a.v b/vlib/v/tests/testdata/sibling_modules_in_src/src/a/a.v
deleted file mode 100644
index 7ebff18c4..000000000
--- a/vlib/v/tests/testdata/sibling_modules_in_src/src/a/a.v
+++ /dev/null
@@ -1,5 +0,0 @@
-module a
-
-pub fn say_a() string {
-	return 'Hello from a!'
-}
diff --git a/vlib/v/tests/testdata/sibling_modules_in_src/src/b/b.v b/vlib/v/tests/testdata/sibling_modules_in_src/src/b/b.v
deleted file mode 100644
index 6a6363328..000000000
--- a/vlib/v/tests/testdata/sibling_modules_in_src/src/b/b.v
+++ /dev/null
@@ -1,7 +0,0 @@
-module b
-
-import a
-
-pub fn say_b() string {
-	return 'b says ${a.say_a()}'
-}
diff --git a/vlib/v/tests/testdata/sibling_modules_in_src/src/main.v b/vlib/v/tests/testdata/sibling_modules_in_src/src/main.v
deleted file mode 100644
index 69c8f8bc1..000000000
--- a/vlib/v/tests/testdata/sibling_modules_in_src/src/main.v
+++ /dev/null
@@ -1,7 +0,0 @@
-module main
-
-import b
-
-fn main() {
-	println(b.say_b())
-}
diff --git a/vlib/v/tests/testdata/sibling_modules_in_src/v.mod b/vlib/v/tests/testdata/sibling_modules_in_src/v.mod
deleted file mode 100644
index 2e5c78260..000000000
--- a/vlib/v/tests/testdata/sibling_modules_in_src/v.mod
+++ /dev/null
@@ -1,3 +0,0 @@
-Module {
-	name: 'sibling_modules_in_src'
-}
diff --git a/vlib/v/util/module.v b/vlib/v/util/module.v
index c28cb7b84..188b5dc71 100644
--- a/vlib/v/util/module.v
+++ b/vlib/v/util/module.v
@@ -147,7 +147,7 @@ fn mod_path_to_full_name(pref_ &pref.Preferences, mod string, path string) !stri
 					path_part := path_parts[j]
 					// we reached a vmod folder
 					if path_part in vmod_folders {
-						mod_full_name := normalize_src_based_mod_name(try_path.split(os.path_separator)[
+						mod_full_name := normalize_base_url_mod_name(try_path.split(os.path_separator)[
 							j + 1..].join('.'), try_path)
 						return mod_full_name
 					}
@@ -172,7 +172,7 @@ fn mod_path_to_full_name(pref_ &pref.Preferences, mod string, path string) !stri
 					break
 				}
 				if last_v_mod > -1 {
-					mod_full_name := normalize_src_based_mod_name(try_path_parts[last_v_mod..].join('.'),
+					mod_full_name := normalize_base_url_mod_name(try_path_parts[last_v_mod..].join('.'),
 						try_path)
 					return if mod_full_name.len < mod.len { mod } else { mod_full_name }
 				}
@@ -188,46 +188,17 @@ fn mod_path_to_full_name(pref_ &pref.Preferences, mod string, path string) !stri
 		rel_mod_path := path.replace(abs_pref_path.all_before_last(os.path_separator) +
 			os.path_separator, '')
 		if rel_mod_path != path {
-			full_mod_name :=
-				normalize_src_based_mod_name(rel_mod_path.replace(os.path_separator, '.'), path)
-			return full_mod_name
+			return normalize_base_url_mod_name(rel_mod_path.replace(os.path_separator, '.'), path)
 		}
 	}
 	return error('module not found')
 }
 
-fn pref_path_to_source_root(pref_ &pref.Preferences) string {
-	pref_path_dir := if os.is_dir(pref_.path) { pref_.path } else { os.dir(pref_.path) }
-	real_pref_path_dir := os.real_path(pref_path_dir)
-	files := os.ls(real_pref_path_dir) or { return real_pref_path_dir }
-	if pref_.should_compile_filtered_files(real_pref_path_dir, files).len == 0 {
-		source_root := source_root_from_vmod_root(real_pref_path_dir) or {
-			os.join_path(real_pref_path_dir, 'src')
-		}
-		if source_root != real_pref_path_dir && os.is_dir(source_root) {
-			return source_root
-		}
-	}
-	return real_pref_path_dir
-}
-
-fn source_root_from_vmod_root(vmod_root string) !string {
-	vmod_path := os.join_path(vmod_root, 'v.mod')
-	if !os.is_file(vmod_path) {
-		return error('module not found')
-	}
-	manifest := vmod.from_file(vmod_path) or { return error('module not found') }
-	return manifest.source_root(vmod_root)
-}
-
-fn configured_base_parts(manifest vmod.Manifest) []string {
-	if manifest.base_url == '' {
-		return []string{}
-	}
-	return os.norm_path(manifest.base_url).split(os.path_separator).filter(it.len > 0 && it != '.')
-}
-
-fn normalize_src_based_mod_name(mod_full_name string, path string) string {
+// normalize_base_url_mod_name strips the `base_url` prefix from `mod_full_name`
+// when the module lives in a folder configured via v.mod's `base_url`. Without
+// this, a module rooted at `<pkg>/source/feature` would be named `pkg.source.feature`
+// instead of `pkg.feature`. The implicit `src/` fallback is intentionally gone.
+fn normalize_base_url_mod_name(mod_full_name string, path string) string {
 	real_path := os.real_path(path)
 	mut mcache := vmod.get_cache()
 	vmod_file_location := mcache.get_by_folder(real_path)
@@ -238,17 +209,17 @@ fn normalize_src_based_mod_name(mod_full_name string, path string) string {
 	if !real_path.starts_with(vmod_prefix) {
 		return mod_full_name
 	}
-	rel_path := real_path.all_after(vmod_prefix)
-	rel_parts := rel_path.split(os.path_separator)
-	mut base_parts := []string{}
-	manifest := vmod.from_file(vmod_file_location.vmod_file) or { vmod.Manifest{} }
-	base_parts = configured_base_parts(manifest)
+	manifest := vmod.from_file(vmod_file_location.vmod_file) or { return mod_full_name }
+	if manifest.base_url == '' {
+		return mod_full_name
+	}
+	base_parts := os.norm_path(manifest.base_url).split(os.path_separator).filter(it.len > 0
+		&& it != '.')
 	if base_parts.len == 0 {
-		if rel_parts.len == 0 || rel_parts[0] != 'src' {
-			return mod_full_name
-		}
-		base_parts = ['src']
+		return mod_full_name
 	}
+	rel_path := real_path.all_after(vmod_prefix)
+	rel_parts := rel_path.split(os.path_separator)
 	if rel_parts.len < base_parts.len || rel_parts[..base_parts.len] != base_parts {
 		return mod_full_name
 	}
diff --git a/vlib/v/vmod/vmod.v b/vlib/v/vmod/vmod.v
index 670dbd348..328cdd678 100644
--- a/vlib/v/vmod/vmod.v
+++ b/vlib/v/vmod/vmod.v
@@ -21,13 +21,14 @@ pub fn (manifest Manifest) resolved_base_url(vmod_root string) string {
 }
 
 // source_root returns the folder where sources are looked up under a `v.mod`.
-// When `base_url` is missing, it preserves the existing `src/` fallback.
+// When `base_url` is set, it points at that folder; otherwise it falls back to
+// the folder containing `v.mod`. The previous implicit `src/` fallback is gone.
 pub fn (manifest Manifest) source_root(vmod_root string) string {
 	base_url := manifest.resolved_base_url(vmod_root)
 	if base_url != '' {
 		return base_url
 	}
-	return os.norm_path(os.join_path(vmod_root, 'src'))
+	return os.norm_path(vmod_root)
 }
 
 // This file provides a caching mechanism for seeking quickly whether a
-- 
2.39.5