tools: fix already installed detection when running v install --once …

…without args (#19838)

cmd/tools/vpm/dependency_test.v

@@ -49,14 +49,17 @@ fn test_install_dependencies_in_module_dir() {
 	}
 	assert v_mod.dependencies == ['markdown', 'pcre', 'https://github.com/spytheman/vtray']
 	// Run `v install`
-	res := os.execute_or_exit('${v} install')
+	mut res := os.execute_or_exit('${v} install --once')
 	assert res.output.contains('Detected v.mod file inside the project directory. Using it...'), res.output
 	assert res.output.contains('Installing `markdown`'), res.output
 	assert res.output.contains('Installing `pcre`'), res.output
 	assert res.output.contains('Installing `vtray`'), res.output
+
 	assert get_mod_name(os.join_path(test_path, 'markdown', 'v.mod')) == 'markdown'
 	assert get_mod_name(os.join_path(test_path, 'pcre', 'v.mod')) == 'pcre'
 	assert get_mod_name(os.join_path(test_path, 'vtray', 'v.mod')) == 'vtray'
+	res = os.execute_or_exit('${v} install --once')
+	assert res.output.contains('All modules are already installed.'), res.output
 }
 
 fn test_resolve_external_dependencies_during_module_install() {

cmd/tools/vpm/install.v

@@ -43,6 +43,7 @@ fn vpm_install(query []string) {
 	vpm_log(@FILE_LINE, @FN, 'Installed modules: ${installed_modules}')
 
 	if installed_modules.len > 0 && settings.is_once {
+		num_to_install := vpm_modules.len + external_modules.len
 		mut already_installed := []string{}
 		if external_modules.len > 0 {
 			mut i_deleted := []int{}
@@ -70,7 +71,7 @@ fn vpm_install(query []string) {
 		}
 		if already_installed.len > 0 {
 			verbose_println('Already installed modules: ${already_installed}')
-			if already_installed.len == query.len {
+			if already_installed.len == num_to_install {
 				println('All modules are already installed.')
 				exit(0)
 			}