tools.vpm: add support for env variable VPM_FAIL_ON_PROMPT, to prev…

…ent getting stuck in test scenarios with conflicting module dir names (#19960)

cmd/tools/vpm/install.v

@@ -233,6 +233,10 @@ fn (m Module) confirm_install() bool {
 	} else {
 		install_version := at_version(if m.version == '' { 'latest' } else { m.version })
 		println('Module `${m.name}${at_version(m.installed_version)}` is already installed at `${m.install_path_fmted}`.')
+		if settings.fail_on_prompt {
+			vpm_error('VPM should not have entered a confirmation prompt.')
+			exit(1)
+		}
 		input := os.input('Replace it with `${m.name}${install_version}`? [Y/n]: ')
 		match input.to_lower() {
 			'', 'y' {

cmd/tools/vpm/install_test.v

@@ -16,6 +16,7 @@ fn testsuite_begin() {
 	os.setenv('VMODULES', test_path, true)
 	os.setenv('VPM_DEBUG', '', true)
 	os.setenv('VPM_NO_INCREMENT', '1', true)
+	os.setenv('VPM_FAIL_ON_PROMPT', '1', true)
 }
 
 fn testsuite_end() {

cmd/tools/vpm/install_version_test.v

@@ -14,6 +14,7 @@ fn testsuite_begin() {
 	os.setenv('VMODULES', test_path, true)
 	os.setenv('VPM_DEBUG', '', true)
 	os.setenv('VPM_NO_INCREMENT', '1', true)
+	os.setenv('VPM_FAIL_ON_PROMPT', '1', true)
 }
 
 fn testsuite_end() {

cmd/tools/vpm/settings.v

@@ -13,6 +13,9 @@ mut:
 	server_urls           []string
 	vmodules_path         string
 	no_dl_count_increment bool
+	// To ensure that some test scenarios with conflicting module directory names do not get stuck in prompts.
+	// It is intended that VPM does not display a prompt when `VPM_FAIL_ON_PROMPT` is set.
+	fail_on_prompt bool
 	// git is used by default. URL installations can specify `--hg`. For already installed modules
 	// and VPM modules that specify a different VCS in their `v.mod`, the VCS is validated separately.
 	vcs VCS
@@ -35,5 +38,6 @@ fn init_settings() VpmSettings {
 		vcs: supported_vcs[if '--hg' in opts { 'hg' } else { 'git' }]
 		vmodules_path: os.vmodules_dir()
 		no_dl_count_increment: os.getenv('CI') != '' || (no_inc_env != '' && no_inc_env != '0')
+		fail_on_prompt: os.getenv('VPM_FAIL_ON_PROMPT') != ''
 	}
 }