fmt: fix removal of used selective and alias imports in modules in $VMODULES dirs (#20977)

Author: ttytm

vlib/v/fmt/fmt.v

@@ -71,8 +71,8 @@ pub fn fmt(file ast.File, mut table ast.Table, pref_ &pref.Preferences, is_debug
 		out: strings.new_builder(1000)
 		out_imports: strings.new_builder(200)
 	}
-	for vpath in os.vmodules_paths() {
-		if file.path.starts_with(vpath) {
+	for p in os.vmodules_paths() {
+		if file.path.starts_with(os.real_path(p)) {
 			f.inside_vmodules = true
 			break
 		}
@@ -374,11 +374,12 @@ pub fn (mut f Fmt) imports(imports []ast.Import) {
 }
 
 pub fn (f Fmt) imp_stmt_str(imp ast.Import) string {
-	if f.inside_vmodules {
-		return imp.source_name
+	normalized_mod := if f.inside_vmodules {
+		imp.source_name
+	} else {
+		mod := if imp.mod.len == 0 { imp.alias } else { imp.mod }
+		mod.all_after('src.') // Ignore the 'src.' folder prefix since src/ folder is root of code
 	}
-	mod := if imp.mod.len == 0 { imp.alias } else { imp.mod }
-	normalized_mod := mod.all_after('src.') // Ignore the 'src.' folder prefix since src/ folder is root of code
 	is_diff := imp.alias != normalized_mod && !normalized_mod.ends_with('.' + imp.alias)
 	mut imp_alias_suffix := if is_diff { ' as ${imp.alias}' } else { '' }
 	mut syms := imp.syms.map(it.name).filter(f.import_syms_used[it])

vlib/v/fmt/fmt_vmodules_test.v

@@ -0,0 +1,26 @@
+import os
+
+const vexe = os.quoted_path(@VEXE)
+const vmodules_tdir = os.join_path(os.vtmp_dir(), 'fmt_vmodules_test')
+const module_tdir = os.join_path(vmodules_tdir, 'foo')
+
+fn testsuite_begin() {
+	os.mkdir_all(module_tdir) or {}
+	os.setenv('VMODULES', vmodules_tdir, true)
+}
+
+fn testsuite_end() {
+	os.rmdir_all(vmodules_tdir) or {}
+}
+
+fn test_fmt_vmodules() {
+	tfile_content := [
+		'import x.json2 as json',
+		'import datatypes { Stack }',
+		'',
+		'const foo = Stack[string]{}',
+		'',
+	].join_lines()
+	os.write_file(os.join_path(module_tdir, 'main.v'), tfile_content)!
+	os.execute_opt('${vexe} fmt -c ${module_tdir}') or { assert false, err.msg() }
+}