Support prelaunchTasks that build with swiftbuild (#1898)

* Support prelaunchTasks that build with swiftbuild

If a prelaunch task is configured to build with --build-system
swiftbuild we need to respect that when setting the program path of the
launch configuration.

Issue: #1830

* swiftPrelaunchBuildTaskArguments shouldn't care about build-system

Author: plemarquand

src/debugger/debugAdapterFactory.ts

@@ -21,7 +21,7 @@ import { SwiftToolchain } from "../toolchain/toolchain";
 import { fileExists } from "../utilities/filesystem";
 import { getErrorDescription, swiftRuntimeEnv } from "../utilities/utilities";
 import { DebugAdapter, LaunchConfigType, SWIFT_LAUNCH_CONFIG_TYPE } from "./debugAdapter";
-import { getTargetBinaryPath } from "./launch";
+import { getTargetBinaryPath, swiftPrelaunchBuildTaskArguments } from "./launch";
 import { getLLDBLibPath, updateLaunchConfigForCI } from "./lldb";
 import { registerLoggingDebugAdapterTracker } from "./logTracker";
 
@@ -133,7 +133,8 @@ export class LLDBDebugConfigurationProvider implements vscode.DebugConfiguration
             launchConfig.program = await getTargetBinaryPath(
                 targetName,
                 buildConfiguration,
-                folderContext
+                folderContext,
+                await swiftPrelaunchBuildTaskArguments(launchConfig, folderContext.workspaceFolder)
             );
             delete launchConfig.target;
         }

src/debugger/launch.ts

@@ -125,14 +125,17 @@ export async function makeDebugConfigurations(
 export async function getTargetBinaryPath(
     targetName: string,
     buildConfiguration: "debug" | "release",
-    folderCtx: FolderContext
+    folderCtx: FolderContext,
+    extraArgs: string[] = []
 ): Promise<string> {
     try {
         // Use dynamic path resolution with --show-bin-path
         const binPath = await folderCtx.toolchain.buildFlags.getBuildBinaryPath(
             folderCtx.folder.fsPath,
             buildConfiguration,
-            folderCtx.workspaceContext.logger
+            folderCtx.workspaceContext.logger,
+            "",
+            extraArgs
         );
         return path.join(binPath, targetName);
     } catch (error) {
@@ -256,7 +259,8 @@ export async function createSnippetConfiguration(
         const binPath = await ctx.toolchain.buildFlags.getBuildBinaryPath(
             ctx.folder.fsPath,
             "debug",
-            ctx.workspaceContext.logger
+            ctx.workspaceContext.logger,
+            "snippet"
         );
 
         return {
@@ -328,3 +332,59 @@ function updateConfigWithNewKeys(
         oldConfig[key] = newConfig[key];
     }
 }
+
+/**
+ * Get the arguments for a launch configuration's preLaunchTask if it's a Swift build task
+ * @param launchConfig The launch configuration to check
+ * @param workspaceFolder The workspace folder context (optional)
+ * @returns Promise<string[] | undefined> the task arguments if it's a Swift build task, undefined otherwise
+ */
+export async function swiftPrelaunchBuildTaskArguments(
+    launchConfig: vscode.DebugConfiguration,
+    workspaceFolder?: vscode.WorkspaceFolder
+): Promise<string[] | undefined> {
+    const preLaunchTask = launchConfig.preLaunchTask;
+
+    if (!preLaunchTask || typeof preLaunchTask !== "string") {
+        return undefined;
+    }
+
+    try {
+        // Fetch all available tasks
+        const allTasks = await vscode.tasks.fetchTasks();
+
+        // Find the task by name
+        const task = allTasks.find(t => {
+            // Check if task name matches (with or without "swift: " prefix)
+            const taskName = t.name;
+            const matches =
+                taskName === preLaunchTask ||
+                taskName === `swift: ${preLaunchTask}` ||
+                `swift: ${taskName}` === preLaunchTask;
+
+            // If workspace folder is specified, also check scope
+            if (workspaceFolder && matches) {
+                return t.scope === workspaceFolder || t.scope === vscode.TaskScope.Workspace;
+            }
+
+            return matches;
+        });
+
+        if (!task) {
+            return undefined;
+        }
+
+        // Check if task type is "swift"
+        if (task.definition.type !== "swift") {
+            return undefined;
+        }
+
+        // Check if args contain "build"
+        const args = (task.definition.args as string[]) || [];
+        const hasBuild = args.includes("build");
+        return hasBuild ? args : undefined;
+    } catch (error) {
+        // Log error but don't throw - return undefined for safety
+        return undefined;
+    }
+}

src/toolchain/BuildFlags.ts

@@ -236,12 +236,14 @@ export class BuildFlags {
     async getBuildBinaryPath(
         workspacePath: string,
         buildConfiguration: "debug" | "release" = "debug",
-        logger: SwiftLogger
+        logger: SwiftLogger,
+        idSuffix: string = "",
+        extraArgs: string[] = []
     ): Promise<string> {
         // Checking the bin path requires a swift process execution, so we maintain a cache.
         // The cache key is based on workspace, configuration, and build arguments.
         const buildArgsHash = JSON.stringify(configuration.buildArguments);
-        const cacheKey = `${workspacePath}:${buildConfiguration}:${buildArgsHash}`;
+        const cacheKey = `${workspacePath}:${buildConfiguration}:${buildArgsHash}${idSuffix}`;
 
         if (BuildFlags.buildPathCache.has(cacheKey)) {
             return BuildFlags.buildPathCache.get(cacheKey)!;
@@ -257,7 +259,7 @@ export class BuildFlags {
         const baseArgs = ["build", "--show-bin-path", "--configuration", buildConfiguration];
         const fullArgs = [
             ...this.withAdditionalFlags(baseArgs),
-            ...binPathAffectingArgs(configuration.buildArguments),
+            ...binPathAffectingArgs([...configuration.buildArguments, ...extraArgs]),
         ];
 
         try {

test/unit-tests/debugger/launch.test.ts

@@ -18,7 +18,7 @@ import { FolderContext } from "@src/FolderContext";
 import { Product, SwiftPackage } from "@src/SwiftPackage";
 import configuration, { FolderConfiguration } from "@src/configuration";
 import { SWIFT_LAUNCH_CONFIG_TYPE } from "@src/debugger/debugAdapter";
-import { makeDebugConfigurations } from "@src/debugger/launch";
+import { makeDebugConfigurations, swiftPrelaunchBuildTaskArguments } from "@src/debugger/launch";
 
 import {
     MockedObject,
@@ -301,3 +301,151 @@ suite("Launch Configurations Test", () => {
         expect(mockLaunchWSConfig.update).to.not.have.been.called;
     });
 });
+
+suite("Swift PreLaunch Build Task Arguments Test", () => {
+    const mockTasks = mockGlobalObject(vscode, "tasks");
+
+    setup(() => {
+        // Reset mocks before each test
+        mockTasks.fetchTasks.reset();
+    });
+
+    test("swiftPrelaunchBuildTaskArguments returns task args for Swift build task", async () => {
+        const expectedArgs = ["build", "--product", "executable", "--build-system"];
+        const mockTask = mockObject<vscode.Task>({
+            name: "swift: Build Debug executable",
+            definition: {
+                type: "swift",
+                args: expectedArgs,
+            },
+            scope: vscode.TaskScope.Workspace,
+            source: "swift",
+            isBackground: false,
+            presentationOptions: {},
+            problemMatchers: [],
+            runOptions: {},
+        });
+
+        mockTasks.fetchTasks.resolves([instance(mockTask)]);
+
+        const launchConfig: vscode.DebugConfiguration = {
+            type: "swift",
+            request: "launch",
+            name: "Debug executable",
+            preLaunchTask: "swift: Build Debug executable",
+        };
+
+        const result = await swiftPrelaunchBuildTaskArguments(launchConfig);
+        expect(result).to.deep.equal(expectedArgs);
+    });
+
+    test("swiftPrelaunchBuildTaskArguments returns undefined for non-Swift task", async () => {
+        const mockTask = mockObject<vscode.Task>({
+            name: "npm: build",
+            definition: {
+                type: "npm",
+                args: ["run", "build"],
+            },
+            scope: vscode.TaskScope.Workspace,
+            source: "npm",
+            isBackground: false,
+            presentationOptions: {},
+            problemMatchers: [],
+            runOptions: {},
+        });
+
+        mockTasks.fetchTasks.resolves([instance(mockTask)]);
+
+        const launchConfig: vscode.DebugConfiguration = {
+            type: "swift",
+            request: "launch",
+            name: "Debug executable",
+            preLaunchTask: "npm: build",
+        };
+
+        const result = await swiftPrelaunchBuildTaskArguments(launchConfig);
+        expect(result).to.be.undefined;
+    });
+
+    test("swiftPrelaunchBuildTaskArguments returns undefined for Swift task without build arg", async () => {
+        const mockTask = mockObject<vscode.Task>({
+            name: "swift: Test",
+            definition: {
+                type: "swift",
+                args: ["test", "--build-system"],
+            },
+            scope: vscode.TaskScope.Workspace,
+            source: "swift",
+            isBackground: false,
+            presentationOptions: {},
+            problemMatchers: [],
+            runOptions: {},
+        });
+
+        mockTasks.fetchTasks.resolves([instance(mockTask)]);
+
+        const launchConfig: vscode.DebugConfiguration = {
+            type: "swift",
+            request: "launch",
+            name: "Debug executable",
+            preLaunchTask: "swift: Test",
+        };
+
+        const result = await swiftPrelaunchBuildTaskArguments(launchConfig);
+        expect(result).to.be.undefined;
+    });
+
+    test("swiftPrelaunchBuildTaskArguments returns undefined for launch config without preLaunchTask", async () => {
+        const launchConfig: vscode.DebugConfiguration = {
+            type: "swift",
+            request: "launch",
+            name: "Debug executable",
+        };
+
+        const result = await swiftPrelaunchBuildTaskArguments(launchConfig);
+        expect(result).to.be.undefined;
+    });
+
+    test("swiftPrelaunchBuildTaskArguments handles errors gracefully", async () => {
+        mockTasks.fetchTasks.rejects(new Error("Failed to fetch tasks"));
+
+        const launchConfig: vscode.DebugConfiguration = {
+            type: "swift",
+            request: "launch",
+            name: "Debug executable",
+            preLaunchTask: "swift: Build Debug executable",
+        };
+
+        const result = await swiftPrelaunchBuildTaskArguments(launchConfig);
+        expect(result).to.be.undefined;
+    });
+
+    test("swiftPrelaunchBuildTaskArguments handles task name variations", async () => {
+        const expectedArgs = ["build", "--product", "executable", "--build-system"];
+        const mockTask = mockObject<vscode.Task>({
+            name: "Build Debug executable",
+            definition: {
+                type: "swift",
+                args: expectedArgs,
+            },
+            scope: vscode.TaskScope.Workspace,
+            source: "swift",
+            isBackground: false,
+            presentationOptions: {},
+            problemMatchers: [],
+            runOptions: {},
+        });
+
+        mockTasks.fetchTasks.resolves([instance(mockTask)]);
+
+        const launchConfig: vscode.DebugConfiguration = {
+            type: "swift",
+            request: "launch",
+            name: "Debug executable",
+            preLaunchTask: "swift: Build Debug executable",
+        };
+
+        const result = await swiftPrelaunchBuildTaskArguments(launchConfig);
+        expect(result).to.deep.equal(expectedArgs);
+    });
+});