From 87e90cc170f23288ae295605df33f545b8c67af5 Mon Sep 17 00:00:00 2001
From: ed cuss <edcussmusic@gmail.com>
Date: Fri, 24 Jul 2026 21:24:27 +0100
Subject: [PATCH 1/3] fix: handle when provided par_collect workers would be 0

---
 src/danom/_stream.py | 2 ++
 tests/test_stream.py | 3 +++
 2 files changed, 5 insertions(+)

diff --git a/src/danom/_stream.py b/src/danom/_stream.py
index 66e3898..223255a 100644
--- a/src/danom/_stream.py
+++ b/src/danom/_stream.py
@@ -472,6 +472,8 @@ def par_collect(self, workers: int = 4, *, use_threads: bool = False) -> tuple[U
         if workers == -1:
             workers = (os.cpu_count() or 5) - 1
 
+        workers = max(workers, 1)
+
         executor_cls = ThreadPoolExecutor if use_threads else ProcessPoolExecutor
 
         batches = [
diff --git a/tests/test_stream.py b/tests/test_stream.py
index 6a56247..d531f02 100644
--- a/tests/test_stream.py
+++ b/tests/test_stream.py
@@ -34,6 +34,9 @@ def _get_attr_collect(stream: Stream, collect_fn: str, kwargs: dict) -> tuple:
         pytest.param("collect", {}, id="simple `collect`"),
         pytest.param("par_collect", {"workers": 4}, id="`par_collect` with workers passed in"),
         pytest.param("par_collect", {"workers": -1}, id="`par_collect` with n-1 workers"),
+        pytest.param(
+            "par_collect", {"workers": 0}, id="`par_collect` with 0 workers falls back to 1 worker"
+        ),
         pytest.param("par_collect", {"use_threads": True}, id="`par_collect` with threads True"),
     ],
 )

From e545874ec3728d1c9032fe9d7a20bda811fc0d2f Mon Sep 17 00:00:00 2001
From: ed cuss <edcussmusic@gmail.com>
Date: Fri, 24 Jul 2026 21:28:46 +0100
Subject: [PATCH 2/3] fix: propagate traceback and input args on map_err

---
 src/danom/_result.py | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/danom/_result.py b/src/danom/_result.py
index f8b431d..69d8d63 100644
--- a/src/danom/_result.py
+++ b/src/danom/_result.py
@@ -264,7 +264,9 @@ def map[**P](self, func: Mappable, *args: P.args, **kwargs: P.kwargs) -> Self:
         return self
 
     def map_err[**P](self, func: Mappable, *args: P.args, **kwargs: P.kwargs) -> Err[E_co]:
-        return Err(func(self.error, *args, **kwargs))
+        return Err(
+            func(self.error, *args, **kwargs), input_args=self.input_args, traceback=self.traceback
+        )
 
     def and_then[**P](self, func: Bindable, *args: P.args, **kwargs: P.kwargs) -> Self:  # noqa: ARG002
         return self

From 1b4af7487b5619fc84f819cb59c808b19ece8f5e Mon Sep 17 00:00:00 2001
From: ed cuss <edcussmusic@gmail.com>
Date: Fri, 24 Jul 2026 21:31:12 +0100
Subject: [PATCH 3/3] docs: don't promise true immutability

---
 src/danom/_stream.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/danom/_stream.py b/src/danom/_stream.py
index 223255a..92ca9e6 100644
--- a/src/danom/_stream.py
+++ b/src/danom/_stream.py
@@ -89,7 +89,7 @@ def __bool__(self) -> bool:
 
 @attrs.define(frozen=True)
 class Stream[T](_BaseStream):
-    """An immutable lazy iterator with functional operations.
+    """A lazy iterator with functional operations.
 
     Why bother?
     -----------