Honor absolute paths for heap and CPU profiler --*-dir/--*-name options

src/jsc/BunCPUProfiler.rs

@@ -178,15 +178,18 @@ fn build_output_path(
         generate_default_filename(&mut filename_buf, is_md_format)?
     };
 
-    // Append directory if specified
+    // Use `join` rather than `append` for both the directory and the filename
+    // so that an absolute `--cpu-prof-dir` or `--cpu-prof-name` is honored:
+    // `append` trims its input as relative to the already-rooted path and
+    // strips the leading separator, whereas `join` resets the accumulated path
+    // when a segment is absolute.
+    // AutoAbsPath uses CheckLength::ASSUME — Err arm is unreachable.
+    // See paths/Path.rs `options::Result` note.
     if !config.dir.is_empty() {
-        // AutoAbsPath uses CheckLength::ASSUME — Err arm is unreachable.
-        // See paths/Path.rs `options::Result` note.
         path.join(&[config.dir]).expect("unreachable");
     }
 
-    // Append filename
-    path.append(filename).expect("unreachable");
+    path.join(&[filename]).expect("unreachable");
 
     Ok(())
 }

src/jsc/BunHeapProfiler.rs

@@ -104,13 +104,17 @@ fn build_output_path(path: &mut AutoAbsPath, config: &HeapProfilerConfig) -> Res
         generate_default_filename(&mut filename_buf, config.text_format)?
     };
 
-    // Append directory if specified
+    // Use `join` rather than `append` for both the directory and the filename
+    // so that an absolute `--heap-prof-dir` or `--heap-prof-name` is honored:
+    // `append` trims its input as relative to the already-rooted path and
+    // strips the leading separator (it also debug-asserts the input is
+    // relative), whereas `join` resets the accumulated path when a segment is
+    // absolute.
     if !config.dir.is_empty() {
-        path.append(config.dir)?;
+        path.join(&[config.dir])?;
     }
 
-    // Append filename
-    path.append(filename)?;
+    path.join(&[filename])?;
     Ok(())
 }
 

test/cli/heap-prof.test.ts

@@ -126,6 +126,65 @@ test("--heap-prof-dir specifies output directory for V8 format", async () => {
   expect(files.length).toBeGreaterThan(0);
 });
 
+test("--heap-prof-dir honors an absolute output directory", async () => {
+  // Two separate directories: one is the CWD, the other is the absolute
+  // target. An absolute --heap-prof-dir must be written to that directory, not
+  // resolved relative to CWD (which stripped the leading separator).
+  using cwdDir = tempDir("heap-prof-abs-cwd", {});
+  using targetDir = tempDir("heap-prof-abs-target", {});
+
+  await using proc = Bun.spawn({
+    cmd: [bunExe(), "--heap-prof", "--heap-prof-dir", String(targetDir), "-e", `console.log("hello");`],
+    cwd: String(cwdDir),
+    env: bunEnv,
+    stdout: "pipe",
+    stderr: "pipe",
+  });
+
+  const [stdout, stderr, exitCode] = await Promise.all([proc.stdout.text(), proc.stderr.text(), proc.exited]);
+
+  expect(stdout.trim()).toBe("hello");
+  expect(stderr).toContain("Heap profile written to:");
+  expect(exitCode).toBe(0);
+
+  // The snapshot must land in the absolute target directory.
+  const targetFiles = Array.from(new Bun.Glob("Heap.*.heapsnapshot").scanSync({ cwd: String(targetDir) }));
+  expect(targetFiles.length).toBeGreaterThan(0);
+
+  // And nothing should have been written anywhere under CWD.
+  const cwdFiles = Array.from(new Bun.Glob("**/Heap.*.heapsnapshot").scanSync({ cwd: String(cwdDir) }));
+  expect(cwdFiles).toEqual([]);
+});
+
+test("--heap-prof-name honors an absolute path", async () => {
+  // An absolute --heap-prof-name must be written verbatim, not resolved
+  // relative to CWD (which stripped the leading separator).
+  using cwdDir = tempDir("heap-prof-name-abs-cwd", {});
+  using targetDir = tempDir("heap-prof-name-abs-target", {});
+  const target = join(String(targetDir), "custom.heapsnapshot");
+
+  await using proc = Bun.spawn({
+    cmd: [bunExe(), "--heap-prof", "--heap-prof-name", target, "-e", `console.log("hello");`],
+    cwd: String(cwdDir),
+    env: bunEnv,
+    stdout: "pipe",
+    stderr: "pipe",
+  });
+
+  const [stdout, stderr, exitCode] = await Promise.all([proc.stdout.text(), proc.stderr.text(), proc.exited]);
+
+  expect(stdout.trim()).toBe("hello");
+  expect(stderr).toContain("Heap profile written to:");
+  expect(exitCode).toBe(0);
+
+  // The snapshot must land at the absolute path.
+  expect(Bun.file(target).size).toBeGreaterThan(0);
+
+  // And nothing should have been written anywhere under CWD.
+  const cwdFiles = Array.from(new Bun.Glob("**/*.heapsnapshot").scanSync({ cwd: String(cwdDir) }));
+  expect(cwdFiles).toEqual([]);
+});
+
 test("--heap-prof-dir specifies output directory for markdown format", async () => {
   using dir = tempDir("heap-prof-md-dir-test", {
     "profiles": {},

test/cli/run/cpu-prof.test.ts

@@ -125,6 +125,40 @@ describe.concurrent("--cpu-prof", () => {
     expect(exitCode).toBe(0);
   });
 
+  test("--cpu-prof-name honors an absolute path", async () => {
+    // An absolute --cpu-prof-name must be written verbatim, not resolved
+    // relative to CWD (which stripped the leading separator).
+    using cwdDir = tempDir("cpu-prof-name-abs-cwd", {
+      "test.js": `
+        function loop() {
+          const end = Date.now() + 100;
+          while (Date.now() < end) {}
+        }
+        loop();
+      `,
+    });
+    using targetDir = tempDir("cpu-prof-name-abs-target", {});
+    const target = join(String(targetDir), "custom.cpuprofile");
+
+    await using proc = Bun.spawn({
+      cmd: [bunExe(), "--cpu-prof", "--cpu-prof-name", target, "test.js"],
+      cwd: String(cwdDir),
+      env: bunEnv,
+      stdout: "inherit",
+      stderr: "inherit",
+    });
+
+    const exitCode = await proc.exited;
+
+    // The profile must land at the absolute path.
+    expect(Bun.file(target).size).toBeGreaterThan(0);
+
+    // And nothing should have been written anywhere under CWD.
+    const cwdFiles = Array.from(new Bun.Glob("**/*.cpuprofile").scanSync({ cwd: String(cwdDir) }));
+    expect(cwdFiles).toEqual([]);
+    expect(exitCode).toBe(0);
+  });
+
   test("--cpu-prof-dir sets custom directory", async () => {
     using dir = tempDir("cpu-prof-dir", {
       "test.js": `