From 83281877f51e32bb244071a9d541c2632f77c1fc Mon Sep 17 00:00:00 2001
From: Kim-Adeline Miguel <51720070+kimadeline@users.noreply.github.com>
Date: Mon, 8 Jun 2020 10:05:18 -0700
Subject: [PATCH] Double-check for interpreters when running diagnostics
 (#12158)

* Get interpreters if hasInterpreters returns false
* Undo ignoreErrors()
* Add unit tests
* Fixed tests
* Newline
---
 news/2 Fixes/11870.md                         |  1 +
 .../diagnostics/checks/pythonInterpreter.ts   |  9 ++++-
 .../checks/pythonInterpreter.unit.test.ts     | 36 +++++++++++++++++--
 3 files changed, 43 insertions(+), 3 deletions(-)
 create mode 100644 news/2 Fixes/11870.md

diff --git a/news/2 Fixes/11870.md b/news/2 Fixes/11870.md
new file mode 100644
index 000000000000..05ada1f0b016
--- /dev/null
+++ b/news/2 Fixes/11870.md	
@@ -0,0 +1 @@
+Double-check for interpreters when running diagnostics before displaying the "Python is not installed" message.
diff --git a/src/client/application/diagnostics/checks/pythonInterpreter.ts b/src/client/application/diagnostics/checks/pythonInterpreter.ts
index f4219f0c8c4b..6040234f7f2a 100644
--- a/src/client/application/diagnostics/checks/pythonInterpreter.ts
+++ b/src/client/application/diagnostics/checks/pythonInterpreter.ts
@@ -67,7 +67,14 @@ export class InvalidPythonInterpreterService extends BaseDiagnosticsService {
         }
 
         const interpreterService = this.serviceContainer.get<IInterpreterService>(IInterpreterService);
-        const hasInterpreters = await interpreterService.hasInterpreters;
+        // hasInterpreters being false can mean one of 2 things:
+        // 1. getInterpreters hasn't returned any interpreters;
+        // 2. getInterpreters hasn't run yet.
+        // We want to make sure that false comes from 1, so we're adding this fix until we refactor interpreter discovery.
+        // Also see https://github.com/microsoft/vscode-python/issues/3023.
+        const hasInterpreters =
+            (await interpreterService.hasInterpreters) ||
+            (await interpreterService.getInterpreters(resource)).length > 0;
 
         if (!hasInterpreters) {
             return [new InvalidPythonInterpreterDiagnostic(DiagnosticCodes.NoPythonInterpretersDiagnostic, resource)];
diff --git a/src/test/application/diagnostics/checks/pythonInterpreter.unit.test.ts b/src/test/application/diagnostics/checks/pythonInterpreter.unit.test.ts
index 0520b9d85bb1..e0dfed705c65 100644
--- a/src/test/application/diagnostics/checks/pythonInterpreter.unit.test.ts
+++ b/src/test/application/diagnostics/checks/pythonInterpreter.unit.test.ts
@@ -31,7 +31,7 @@ import { IConfigurationService, IDisposableRegistry, IPythonSettings } from '../
 import { noop } from '../../../../client/common/utils/misc';
 import { IInterpreterHelper, IInterpreterService } from '../../../../client/interpreter/contracts';
 import { IServiceContainer } from '../../../../client/ioc/types';
-import { InterpreterType } from '../../../../client/pythonEnvironments/discovery/types';
+import { InterpreterType, PythonInterpreter } from '../../../../client/pythonEnvironments/discovery/types';
 
 suite('Application Diagnostics - Checks Python Interpreter', () => {
     let diagnosticService: IDiagnosticsService;
@@ -130,7 +130,7 @@ suite('Application Diagnostics - Checks Python Interpreter', () => {
             expect(diagnostics).to.be.deep.equal([]);
             settings.verifyAll();
         });
-        test('Should return diagnostics if there are no interpreters', async () => {
+        test('Should return diagnostics if there are no interpreters after double-checking', async () => {
             settings
                 .setup((s) => s.disableInstallationChecks)
                 .returns(() => false)
@@ -139,6 +139,10 @@ suite('Application Diagnostics - Checks Python Interpreter', () => {
                 .setup((i) => i.hasInterpreters)
                 .returns(() => Promise.resolve(false))
                 .verifiable(typemoq.Times.once());
+            interpreterService
+                .setup((i) => i.getInterpreters(undefined))
+                .returns(() => Promise.resolve([]))
+                .verifiable(typemoq.Times.once());
 
             const diagnostics = await diagnosticService.diagnose(undefined);
             expect(diagnostics).to.be.deep.equal(
@@ -148,6 +152,34 @@ suite('Application Diagnostics - Checks Python Interpreter', () => {
             settings.verifyAll();
             interpreterService.verifyAll();
         });
+        test('Should return empty diagnostics if there are interpreters after double-checking', async () => {
+            const interpreter: PythonInterpreter = { type: InterpreterType.Unknown } as any;
+
+            settings
+                .setup((s) => s.disableInstallationChecks)
+                .returns(() => false)
+                .verifiable(typemoq.Times.once());
+            interpreterService
+                .setup((i) => i.hasInterpreters)
+                .returns(() => Promise.resolve(false))
+                .verifiable(typemoq.Times.once());
+            interpreterService
+                .setup((i) => i.getInterpreters(undefined))
+                .returns(() => Promise.resolve([interpreter]))
+                .verifiable(typemoq.Times.once());
+            interpreterService
+                .setup((i) => i.getActiveInterpreter(typemoq.It.isAny()))
+                .returns(() => {
+                    return Promise.resolve(interpreter);
+                })
+                .verifiable(typemoq.Times.once());
+
+            const diagnostics = await diagnosticService.diagnose(undefined);
+
+            expect(diagnostics).to.be.deep.equal([], 'not the same');
+            settings.verifyAll();
+            interpreterService.verifyAll();
+        });
         test('Should return invalid diagnostics if there are interpreters but no current interpreter', async () => {
             settings
                 .setup((s) => s.disableInstallationChecks)