Check dotnet path without which or where first

vscode-dotnet-runtime-extension/src/extension.ts

@@ -515,6 +515,17 @@ export function activate(vsCodeContext: vscode.ExtensionContext, extensionContex
         const validator = new DotnetConditionValidator(workerContext, utilContext);
         const finder = new DotnetPathFinder(workerContext, utilContext);
 
+        const dotnetOnShellSpawn = (await finder.findDotnetFastFromListOnly())?.[0] ?? '';
+        if (dotnetOnShellSpawn)
+        {
+            const validatedShellSpawn = await getPathIfValid(dotnetOnShellSpawn, validator, commandContext);
+            if (validatedShellSpawn)
+            {
+                loggingObserver.dispose();
+                return { dotnetPath: validatedShellSpawn };
+            }
+        }
+
         const dotnetsOnPATH = await finder.findRawPathEnvironmentSetting();
         for (const dotnetPath of dotnetsOnPATH ?? [])
         {

vscode-dotnet-runtime-library/src/Acquisition/DotnetPathFinder.ts

@@ -92,6 +92,23 @@ export class DotnetPathFinder implements IDotnetPathFinder
         return undefined;
     }
 
+    /**
+     * @remarks This only checks dotnet --list-runtimes or --list-sdks, so it can be more performant for the base case.
+     * This allows skipping which, where, and also does not rely on --info which is slower because it shells to the SDK instead of just being the host.
+     * @returns The path to the dotnet executable, which may be a symlink to the actual executable.
+     */
+    public async findDotnetFastFromListOnly(): Promise<string[] | undefined>
+    {
+        const oldLookup = process.env.DOTNET_MULTILEVEL_LOOKUP;
+        try {
+            process.env.DOTNET_MULTILEVEL_LOOKUP = '0'; // make it so --list-runtimes only finds the runtimes on that path: https://learn.microsoft.com/en-us/dotnet/core/compatibility/deployment/7.0/multilevel-lookup#reason-for-change
+            const finalPath = await this.getTruePath(['dotnet']);
+            return this.returnWithRestoringEnvironment(finalPath, 'DOTNET_MULTILEVEL_LOOKUP', oldLookup);
+        } finally {
+            process.env.DOTNET_MULTILEVEL_LOOKUP = oldLookup; // Ensure the environment variable is always restored
+        }
+    }
+
     /**
      *
      * @returns A set of the path environment variable(s) for which or where dotnet, which may need to be converted to the actual path if it points to a polymorphic executable.