Support `bun run --if-present` (#6248)

* Support --if-present
Closes #5670

* More robust tests, handle more cases

2 files changed, 120 insertions, 1 deletions

diff --git a/test/cli/run/if-present.test.ts b/test/cli/run/if-present.test.ts
new file mode 100644
index 000000000..120970b46
--- /dev/null
+++ b/test/cli/run/if-present.test.ts
@@ -0,0 +1,119 @@
+import { describe, test, expect, beforeAll } from "bun:test";
+import { spawnSync } from "bun";
+import { bunEnv, bunExe, tempDirWithFiles } from "harness";
+
+let cwd: string;
+
+beforeAll(() => {
+  cwd = tempDirWithFiles("--if-present", {
+    "present.js": "console.log('Here!');",
+    "package.json": JSON.stringify({
+      "name": "present",
+      "scripts": {
+        "present": "echo 'Here!'",
+      },
+    }),
+  });
+});
+
+describe("bun", () => {
+  test("should error with missing script", () => {
+    const { exitCode, stdout, stderr } = spawnSync({
+      cwd,
+      cmd: [bunExe(), "notpresent"],
+      env: bunEnv,
+      stdout: "pipe",
+      stderr: "pipe",
+    });
+    expect(stdout.toString()).toBeEmpty();
+    expect(stderr.toString()).toMatch(/script not found/);
+    expect(exitCode).toBe(1);
+  });
+  test("should error with missing module", () => {
+    const { exitCode, stdout, stderr } = spawnSync({
+      cwd,
+      cmd: [bunExe(), "./notpresent.js"],
+      env: bunEnv,
+      stdout: "pipe",
+      stderr: "pipe",
+    });
+    expect(stdout.toString()).toBeEmpty();
+    expect(stderr.toString()).toMatch(/module not found/);
+    expect(exitCode).toBe(1);
+  });
+  test("should error with missing file", () => {
+    const { exitCode, stdout, stderr } = spawnSync({
+      cwd,
+      cmd: [bunExe(), "/path/to/notpresent.txt"],
+      env: bunEnv,
+      stdout: "pipe",
+      stderr: "pipe",
+    });
+    expect(stdout.toString()).toBeEmpty();
+    expect(stderr.toString()).toMatch(/file not found/);
+    expect(exitCode).toBe(1);
+  });
+});
+
+describe("bun --if-present", () => {
+  test("should not error with missing script", () => {
+    const { exitCode, stdout, stderr } = spawnSync({
+      cwd,
+      cmd: [bunExe(), "--if-present", "notpresent"],
+      env: bunEnv,
+      stdout: "pipe",
+      stderr: "pipe",
+    });
+    expect(stdout.toString()).toBeEmpty();
+    expect(stderr.toString()).toBeEmpty();
+    expect(exitCode).toBe(0);
+  });
+  test("should not error with missing module", () => {
+    const { exitCode, stdout, stderr } = spawnSync({
+      cwd,
+      cmd: [bunExe(), "--if-present", "./notpresent.js"],
+      env: bunEnv,
+      stdout: "pipe",
+      stderr: "pipe",
+    });
+    expect(stdout.toString()).toBeEmpty();
+    expect(stderr.toString()).toBeEmpty();
+    expect(exitCode).toBe(0);
+  });
+  test("should not error with missing file", () => {
+    const { exitCode, stdout, stderr } = spawnSync({
+      cwd,
+      cmd: [bunExe(), "--if-present", "/path/to/notpresent.txt"],
+      env: bunEnv,
+      stdout: "pipe",
+      stderr: "pipe",
+    });
+    expect(stdout.toString()).toBeEmpty();
+    expect(stderr.toString()).toBeEmpty();
+    expect(exitCode).toBe(0);
+  });
+  test("should run present script", () => {
+    const { exitCode, stdout, stderr } = spawnSync({
+      cwd,
+      cmd: [bunExe(), "run", "present"],
+      env: bunEnv,
+      stdout: "pipe",
+      stderr: "pipe",
+    });
+    expect(stdout.toString()).toMatch(/Here!/);
+    expect(stderr.toString()).not.toBeEmpty();
+    expect(exitCode).toBe(0);
+  });
+  test("should run present module", () => {
+    const { exitCode, stdout, stderr } = spawnSync({
+      cwd,
+      cmd: [bunExe(), "run", "present.js"],
+      env: bunEnv,
+      stdout: "pipe",
+      stderr: "pipe",
+    });
+    expect(stdout.toString()).toMatch(/Here!/);
+    expect(stderr.toString()).toBeEmpty();
+    expect(exitCode).toBe(0);
+  });
+});
diff --git a/test/harness.ts b/test/harness.ts
index 16d04c1b4..77b4b4f43 100644
--- a/test/harness.ts
+++ b/test/harness.ts
@@ -84,7 +84,7 @@ export function hideFromStackTrace(block: CallableFunction) {
   });
 }
 
-export function tempDirWithFiles(basename: string, files: Record<string, string | Record<string, string>>) {
+export function tempDirWithFiles(basename: string, files: Record<string, string | Record<string, string>>): string {
   var fs = require("fs");
   var path = require("path");
   var { tmpdir } = require("os");