run_before_script: Use chunk-based output

Author: tony

src/tmuxp/util.py

@@ -24,7 +24,7 @@
 PY2 = sys.version_info[0] == 2
 
 
-def run_before_script(
+def run_before_script2(
     script_file: str | pathlib.Path,
     cwd: pathlib.Path | None = None,
 ) -> int:
@@ -96,6 +96,73 @@ def run_before_script(
     return return_code
 
 
+def run_before_script(
+    script_file: str | pathlib.Path,
+    cwd: pathlib.Path | None = None,
+) -> int:
+    script_cmd = shlex.split(str(script_file))
+
+    try:
+        proc = subprocess.Popen(
+            script_cmd,
+            cwd=cwd,
+            stdout=subprocess.PIPE,
+            stderr=subprocess.PIPE,
+            text=True,  # still decode to str
+            errors="backslashreplace",
+            bufsize=0,  # unbuffered in Python, best effort
+        )
+    except FileNotFoundError as e:
+        raise exc.BeforeLoadScriptNotExists(
+            e,
+            os.path.abspath(script_file),  # NOQA: PTH100
+        ) from e
+
+    out_buffer = []
+    err_buffer = []
+    is_out_tty = sys.stdout.isatty()
+    is_err_tty = sys.stderr.isatty()
+
+    # We'll read in chunks from both stdout and stderr in a loop.
+    # This example uses a single loop that tries to read both streams
+    # repeatedly. For large outputs, consider threading or select().
+
+    while True:
+        return_code = proc.poll()
+
+        # Read some data from stdout (if available)
+        chunk_out = proc.stdout.read(1024) if proc.stdout else ""
+        if chunk_out:
+            out_buffer.append(chunk_out)
+            if is_out_tty:
+                sys.stdout.write(chunk_out)
+                sys.stdout.flush()
+
+        # Read some data from stderr (if available)
+        chunk_err = proc.stderr.read(1024) if proc.stderr else ""
+        if chunk_err:
+            err_buffer.append(chunk_err)
+            if is_err_tty:
+                sys.stderr.write(chunk_err)
+                sys.stderr.flush()
+
+        if return_code is not None and not chunk_out and not chunk_err:
+            # No more data from pipes, process ended
+            break
+
+    return_code = proc.wait()
+
+    if return_code != 0:
+        stderr_str = "".join(err_buffer).strip()
+        raise exc.BeforeLoadScriptError(
+            return_code,
+            os.path.abspath(script_file),  # NOQA: PTH100
+            stderr_str,
+        )
+
+    return return_code
+
+
 def oh_my_zsh_auto_title() -> None:
     """Give warning and offer to fix ``DISABLE_AUTO_TITLE``.