Fix missing Test Result output on Linux when using print

node-pty on Linux suffers from a long standing issue where the last
chunk of output before a program exits is sometimes dropped, especially
if that program produces a lot of output immediately before exiting.
See microsoft/node-pty#72

We can work around this by delegating to bash and forwarding the exit
code. This causes the underlying pipe to be fully flushed before we
recieve the exit event. This workaround was suggested here:
chjj/pty.js#110 (comment)

Swift currently ships on Ubuntu Debian and Fedora which all come with
`bash`. This patch assumes additional Linux distributions added in the
future will ship with `bash`.

Issue: #1393

Author: plemarquand

assets/test/defaultPackage/Tests/PackageTests/PackageTests.swift

@@ -102,6 +102,14 @@ struct MixedSwiftTestingSuite {
   }
   #expect(2 == 3)
 }
+
+@Test func testLotsOfOutput() {
+  var string = ""
+  for i in 1...100_000 {
+    string += "\(i)\n"
+  }
+  print(string)
+}
 #endif
 
 #if swift(>=6.1)

src/TestExplorer/TestRunArguments.ts

@@ -93,11 +93,12 @@ export class TestRunArguments {
                 const terminator = hasChildren ? "/" : "$";
                 // Debugging XCTests requires exact matches, so we don't need a trailing terminator.
                 return isDebug ? arg.id : `${arg.id}${terminator}`;
-            } else {
+            } else if (hasChildren) {
                 // Append a trailing slash to match a suite name exactly.
                 // This prevents TestTarget.MySuite matching TestTarget.MySuite2.
                 return `${arg.id}/`;
             }
+            return arg.id;
         });
     }
 

src/tasks/SwiftProcess.ts

@@ -16,6 +16,7 @@ import type * as nodePty from "node-pty";
 import * as vscode from "vscode";
 
 import { requireNativeModule } from "../utilities/native";
+import { regexEscapedString } from "../utilities/utilities";
 const { spawn } = requireNativeModule<typeof nodePty>("node-pty");
 
 export interface SwiftProcess {
@@ -98,14 +99,17 @@ export class SwiftPtyProcess implements SwiftProcess {
             // The pty process hangs on Windows when debugging the extension if we use conpty
             // See https://github.com/microsoft/node-pty/issues/640
             const useConpty = isWindows && process.env["VSCODE_DEBUG"] === "1" ? false : true;
-            this.spawnedProcess = spawn(this.command, this.args, {
+
+            this.spawnedProcess = this.spawnProcess({
+                // this.spawnedProcess = spawn(this.command, this.args, {
                 cwd: this.options.cwd,
                 env: { ...process.env, ...this.options.env },
                 useConpty,
                 // https://github.com/swiftlang/vscode-swift/issues/1074
                 // Causing weird truncation issues
                 cols: isWindows ? 4096 : undefined,
             });
+
             this.spawnEmitter.fire();
             this.spawnedProcess.onData(data => {
                 this.writeEmitter.fire(data);
@@ -152,4 +156,34 @@ export class SwiftPtyProcess implements SwiftProcess {
     onDidThrowError: vscode.Event<Error> = this.errorEmitter.event;
 
     onDidClose: vscode.Event<number | void> = this.closeEmitter.event;
+
+    private spawnProcess(
+        options: nodePty.IPtyForkOptions | nodePty.IWindowsPtyForkOptions
+    ): nodePty.IPty {
+        // node-pty on Linux suffers from a long standing issue where the last
+        // chunk of output before a program exits is sometimes dropped, especially
+        // if that program produces a lot of output immediately before exiting.
+        // See https://github.com/microsoft/node-pty/issues/72
+
+        // We can work around this by delegating to bash and forwarding the exit
+        // code. This causes the underlying pipe to be fully flushed before we recieve
+        // the exit event. This workaround was suggested here:
+        // https://github.com/chjj/pty.js/pull/110#issuecomment-406470140
+        if (process.platform === "linux") {
+            // In order to be passed as an argument to bash the command arguments
+            // should not be escaped with the full set of characters normally escaped
+            // using the command line directly. Unescape and reescape the string with
+            // a more limited set of characters.
+            const commandArgs = regexEscapedString(
+                this.args.join(" ").replaceAll(/\\(.)/g, "$1"),
+                new Set(["[", "]", ".", "$", "^", "?", "|", "/", ":", "\\"]),
+                "\\\\\\"
+            );
+
+            const args = ["-c", `${this.command} ${commandArgs}; exit $?`];
+            return spawn("bash", args, options);
+        } else {
+            return spawn(this.command, this.args, options);
+        }
+    }
 }

src/utilities/utilities.ts

@@ -350,11 +350,15 @@ const regexEscapedCharacters = new Set(["(", ")", "[", "]", ".", "$", "^", "?",
  * @param string A string to escape
  * @returns The escaped string
  */
-export function regexEscapedString(string: string, omitting?: Set<string>): string {
+export function regexEscapedString(
+    string: string,
+    omitting?: Set<string>,
+    escape: string = "\\"
+): string {
     let result = "";
     for (const c of string) {
         if (regexEscapedCharacters.has(c) && (!omitting || !omitting.has(c))) {
-            result += `\\${c}`;
+            result += `${escape}${c}`;
         } else {
             result += c;
         }

test/integration-tests/testexplorer/TestExplorerIntegration.test.ts

@@ -190,6 +190,7 @@ suite("Test Explorer Suite", function () {
                         ["testPassing()", "testFailing()", "testDisabled()"],
                         "testWithKnownIssue()",
                         "testWithKnownIssueAndUnknownIssue()",
+                        "testLotsOfOutput()",
                         "testAttachment()",
                         "DuplicateSuffixTests",
                         ["testPassing()", "testPassingSuffix()"],
@@ -230,6 +231,25 @@ suite("Test Explorer Suite", function () {
                 }
             });
 
+            test("captures lots of output", async () => {
+                const testRun = await runTest(
+                    testExplorer,
+                    TestKind.standard,
+                    "PackageTests.testLotsOfOutput()"
+                );
+
+                assertTestResults(testRun, {
+                    passed: ["PackageTests.testLotsOfOutput()"],
+                });
+
+                // Right now the swift-testing "test run complete" text is being emitted
+                // in the middle of the print, so the last line is actually end end of our
+                // huge string. If they fix this in future this `find` ensures the test wont break.
+                const needle = "100000";
+                const lastOutputLine = testRun.runState.output.find(row => row.trim() === needle);
+                assert.equal(lastOutputLine?.trim(), needle);
+            });
+
             test("attachments", async function () {
                 // Attachments were introduced in 6.1
                 if (workspaceContext.swiftVersion.isLessThan(new Version(6, 1, 0))) {

test/integration-tests/testexplorer/TestRunArguments.test.ts

@@ -240,7 +240,7 @@ suite("TestRunArguments Suite", () => {
         const testArgs = new TestRunArguments(runRequestByIds([anotherSwiftTestId]), false);
         assertRunArguments(testArgs, {
             xcTestArgs: [],
-            swiftTestArgs: [`${anotherSwiftTestId}/`],
+            swiftTestArgs: [anotherSwiftTestId],
             testItems: [swiftTestSuiteId, testTargetId, anotherSwiftTestId],
         });
     });