Initial version of .NET Solution Launcher

Startup project and solution configuration (Debug|x64, Test|x64, ...) in
the status bar, with build and debug tasks that pass both configuration
and platform. Made for DotRush, whose build never passes -p:Platform and
whose status item shows the configuration but not the project.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0169iPWwKHZoBTNN9qwXiwqk

src/launch.ts

@@ -0,0 +1,85 @@
+import * as vscode from 'vscode';
+import * as fs from 'fs';
+import * as path from 'path';
+import { SolutionModel } from './model';
+import { taskLabel } from './tasks';
+
+export const LAUNCH_NAME = '.NET Solution: Debug startup project';
+
+function launchSettings() {
+    return vscode.workspace.getConfiguration('dotnetSolution');
+}
+
+/**
+ * A complete launch configuration for the startup project under the active configuration.
+ *
+ * `program` is the apphost .exe when the project makes one, because vsdbg wants an
+ * executable. Projects without an apphost run through the dotnet host instead. The
+ * debugger options DotRush normally fills in (justMyCode, symbol servers, console) are
+ * left out so its own provider still adds them.
+ */
+export async function buildLaunchConfiguration(
+    model: SolutionModel, options: { noDebug?: boolean; preLaunchTask?: string }): Promise<vscode.DebugConfiguration> {
+    const active = model.active;
+    if (!active) {
+        throw new Error('No startup project selected.');
+    }
+    const target = await model.resolveTarget();
+    const settings = launchSettings();
+    const userArgs = settings.get<string[]>('launch.args', []);
+    const cwd = settings.get<string>('launch.cwd', '') || target.targetDir.replace(/[\\/]+$/, '');
+    const console = settings.get<string>('launch.console', 'internalConsole');
+
+    const program = target.executablePath ?? 'dotnet';
+    const args = target.executablePath ? userArgs : [target.targetPath, ...userArgs];
+
+    return {
+        name: `${active.project.info.name} (${active.solutionConfiguration.configuration}|${active.solutionPlatform})`,
+        type: settings.get<string>('debugType', 'coreclr'),
+        request: 'launch',
+        program,
+        args,
+        cwd,
+        env: settings.get<Record<string, string>>('launch.env', {}),
+        console,
+        noDebug: options.noDebug ?? false,
+        preLaunchTask: options.preLaunchTask,
+        // DotRush looks for Properties/launchSettings.json next to *its* startup project;
+        // this one is synced, so that still works. Point it explicitly anyway.
+        launchSettingsFilePath: launchSettingsPath(active.project.info.fsPath),
+    };
+}
+
+function launchSettingsPath(projectPath: string): string | undefined {
+    const candidate = path.join(path.dirname(projectPath), 'Properties', 'launchSettings.json');
+    return fs.existsSync(candidate) ? candidate : undefined;
+}
+
+/** The static entry written to launch.json: values come back through `${command:…}` at launch time. */
+export function launchJsonEntry(): Record<string, unknown> {
+    return {
+        name: LAUNCH_NAME,
+        type: launchSettings().get<string>('debugType', 'coreclr'),
+        request: 'launch',
+        program: '${command:dotnetSolution.activeProgram}',
+        args: [],
+        cwd: '${command:dotnetSolution.activeTargetDir}',
+        preLaunchTask: taskLabel('build'),
+    };
+}
+
+/**
+ * Offers the dynamic "debug the startup project" entry in the Run and Debug dropdown,
+ * and fills in `program` for launch.json entries that use this extension's variables
+ * but omitted them.
+ */
+export class SolutionDebugConfigurationProvider implements vscode.DebugConfigurationProvider {
+    constructor(private readonly model: SolutionModel) { }
+
+    async provideDebugConfigurations(): Promise<vscode.DebugConfiguration[]> {
+        if (!this.model.active) {
+            return [];
+        }
+        return [launchJsonEntry() as vscode.DebugConfiguration];
+    }
+}