Improve getting started experience when starting on a fresh macOS (#20789)

Closes #20635

- Suggest to install from `python.org` if brew is not available
- Do not suggest irrelevant prompts

Author: Kartik Raj

src/client/common/utils/localize.ts

@@ -204,9 +204,13 @@ export namespace Interpreters {
     export const selectInterpreterTip = l10n.t(
         'Tip: you can change the Python interpreter used by the Python extension by clicking on the Python version in the status bar',
     );
-    export const installPythonTerminalMessage = l10n.t(
+    export const installPythonTerminalMessageLinux = l10n.t(
         '💡 Please try installing the python package using your package manager. Alternatively you can also download it from https://www.python.org/downloads',
     );
+
+    export const installPythonTerminalMacMessage = l10n.t(
+        '💡 Brew does not seem to be available. Please try to download Python from https://www.python.org/downloads. Alternatively, you can install the python package using some other package manager which is available.',
+    );
     export const changePythonInterpreter = l10n.t('Change Python Interpreter');
     export const selectedPythonInterpreter = l10n.t('Selected Python Interpreter');
 }

src/client/interpreter/configuration/interpreterSelector/commands/installPython/installPythonViaTerminal.ts

@@ -55,9 +55,13 @@ export class InstallPythonViaTerminal implements IExtensionSingleActivationServi
 
     public async _installPythonOnUnix(os: OSType.Linux | OSType.OSX): Promise<void> {
         const commands = await this.getCommands(os);
+        const installMessage =
+            os === OSType.OSX
+                ? Interpreters.installPythonTerminalMacMessage
+                : Interpreters.installPythonTerminalMessageLinux;
         const terminal = this.terminalManager.createTerminal({
             name: 'Python',
-            message: commands.length ? undefined : Interpreters.installPythonTerminalMessage,
+            message: commands.length ? undefined : installMessage,
         });
         terminal.show(true);
         await waitForTerminalToStartup();
@@ -69,31 +73,36 @@ export class InstallPythonViaTerminal implements IExtensionSingleActivationServi
 
     private async getCommands(os: OSType.Linux | OSType.OSX) {
         if (os === OSType.OSX) {
-            return this.packageManagerCommands[PackageManagers.brew];
+            return this.getCommandsForPackageManagers([PackageManagers.brew]);
         }
-        return this.getCommandsForLinux();
+        if (os === OSType.Linux) {
+            return this.getCommandsForPackageManagers([PackageManagers.apt, PackageManagers.dnf]);
+        }
+        throw new Error('OS not supported');
     }
 
-    private async getCommandsForLinux() {
-        for (const packageManager of [PackageManagers.apt, PackageManagers.dnf]) {
-            let isPackageAvailable = false;
-            try {
-                const which = require('which') as typeof whichTypes;
-                const resolvedPath = await which(packageManager);
-                traceVerbose(`Resolved path to ${packageManager} module:`, resolvedPath);
-                isPackageAvailable = resolvedPath.trim().length > 0;
-            } catch (ex) {
-                traceVerbose(`${packageManager} not found`, ex);
-                isPackageAvailable = false;
-            }
-            if (isPackageAvailable) {
+    private async getCommandsForPackageManagers(packageManagers: PackageManagers[]) {
+        for (const packageManager of packageManagers) {
+            if (await isPackageAvailable(packageManager)) {
                 return this.packageManagerCommands[packageManager];
             }
         }
         return [];
     }
 }
 
+async function isPackageAvailable(packageManager: PackageManagers) {
+    try {
+        const which = require('which') as typeof whichTypes;
+        const resolvedPath = await which(packageManager);
+        traceVerbose(`Resolved path to ${packageManager} module:`, resolvedPath);
+        return resolvedPath.trim().length > 0;
+    } catch (ex) {
+        traceVerbose(`${packageManager} not found`, ex);
+        return false;
+    }
+}
+
 async function waitForTerminalToStartup() {
     // Sometimes the terminal takes some time to start up before it can start accepting input.
     await sleep(100);

src/client/pythonEnvironments/base/locators/lowLevel/macDefaultLocator.ts

@@ -13,7 +13,7 @@ export function isMacDefaultPythonPath(pythonPath: string): boolean {
         return false;
     }
 
-    const defaultPaths = ['python', '/usr/bin/python'];
+    const defaultPaths = ['/usr/bin/python'];
 
     return defaultPaths.includes(pythonPath) || pythonPath.startsWith('/usr/bin/python2');
 }

src/test/configuration/interpreterSelector/commands/installPythonViaTerminal.unit.test.ts

@@ -96,15 +96,22 @@ suite('Install Python via Terminal', () => {
         await installPythonCommand.activate();
         await installCommandHandler!();
 
-        expect(message).to.be.equal(Interpreters.installPythonTerminalMessage);
+        expect(message).to.be.equal(Interpreters.installPythonTerminalMessageLinux);
     });
 
-    test('Sends expected commands on Mac when InstallPythonOnMac command is executed if no dnf is available', async () => {
+    test('Sends expected commands on Mac when InstallPythonOnMac command is executed if brew is available', async () => {
         let installCommandHandler: () => Promise<void>;
         when(cmdManager.registerCommand(Commands.InstallPythonOnMac, anything())).thenCall((_, cb) => {
             installCommandHandler = cb;
             return TypeMoq.Mock.ofType<IDisposable>().object;
         });
+        rewiremock('which').with((cmd: string) => {
+            if (cmd === 'brew') {
+                return 'path/to/brew';
+            }
+            throw new Error('Command not found');
+        });
+
         await installPythonCommand.activate();
         when(terminalService.sendText('brew install python3')).thenResolve();
 
@@ -113,4 +120,21 @@ suite('Install Python via Terminal', () => {
         verify(terminalService.sendText('brew install python3')).once();
         expect(message).to.be.equal(undefined);
     });
+
+    test('Creates terminal with appropriate message when InstallPythonOnMac command is executed if brew is not available', async () => {
+        let installCommandHandler: () => Promise<void>;
+        when(cmdManager.registerCommand(Commands.InstallPythonOnMac, anything())).thenCall((_, cb) => {
+            installCommandHandler = cb;
+            return TypeMoq.Mock.ofType<IDisposable>().object;
+        });
+        rewiremock('which').with((_cmd: string) => {
+            throw new Error('Command not found');
+        });
+
+        await installPythonCommand.activate();
+
+        await installCommandHandler!();
+
+        expect(message).to.be.equal(Interpreters.installPythonTerminalMacMessage);
+    });
 });

src/test/pythonEnvironments/base/locators/lowLevel/macDefaultLocator.unit.test.ts

@@ -18,8 +18,6 @@ suite('isMacDefaultPythonPath', () => {
     });
 
     const testCases: { path: string; os: osUtils.OSType; expected: boolean }[] = [
-        { path: 'python', os: osUtils.OSType.OSX, expected: true },
-        { path: 'python', os: osUtils.OSType.Windows, expected: false },
         { path: '/usr/bin/python', os: osUtils.OSType.OSX, expected: true },
         { path: '/usr/bin/python', os: osUtils.OSType.Linux, expected: false },
         { path: '/usr/bin/python2', os: osUtils.OSType.OSX, expected: true },