From ccc279e56ac44077cb5d35344c59d5aec7fab971 Mon Sep 17 00:00:00 2001
From: thomas-samoht <54805624+thomas-samoht@users.noreply.github.com>
Date: Wed, 21 Oct 2026 10:53:07 +0200
Subject: [PATCH] Reject duplicate streams

---
 CHANGELOG.md                        |  3 +++
 gfmodules/logging/config.py         | 12 +++++++++++-
 gfmodules/logging/config_builder.py |  2 +-
 tests/test_config.py                | 13 +++++++++++++
 tests/test_config_builder.py        | 11 -----------
 5 files changed, 28 insertions(+), 13 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 3119923..cc1ce85 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -11,6 +11,9 @@
   behavior.
 - The debug stream on the log server now honours `include_traces`, so
   `include_traces=False` keeps tracebacks off the log server as well.
+- `ConfigLogging` now rejects a stream named more than once in
+  `console_streams` or `syslog_streams`. The duplicate was silently dropped
+  before, which hid a typo or a merge mistake in the configuration.
 
 ### Added
 
diff --git a/gfmodules/logging/config.py b/gfmodules/logging/config.py
index b3f708a..8a66af0 100644
--- a/gfmodules/logging/config.py
+++ b/gfmodules/logging/config.py
@@ -1,4 +1,6 @@
-from pydantic import BaseModel, Field
+from collections import Counter
+
+from pydantic import BaseModel, Field, ValidationInfo, field_validator
 
 
 class ConfigLogging(BaseModel):
@@ -15,3 +17,11 @@ class ConfigLogging(BaseModel):
     # Empty leaves stdout silent.
     console_streams: list[str] = Field(default=["app", "siem"])
     syslog_streams: list[str] = Field(default=["app", "siem", "public_inspect"])
+
+    @field_validator("console_streams", "syslog_streams")
+    @classmethod
+    def _reject_duplicate_streams(cls, names: list[str], info: ValidationInfo) -> list[str]:
+        duplicates = [name for name, count in Counter(names).items() if count > 1]
+        if duplicates:
+            raise ValueError(f"duplicate {info.field_name} {duplicates}")
+        return names
diff --git a/gfmodules/logging/config_builder.py b/gfmodules/logging/config_builder.py
index 125cc90..cbe3ab1 100644
--- a/gfmodules/logging/config_builder.py
+++ b/gfmodules/logging/config_builder.py
@@ -16,7 +16,7 @@ def _selected(setting: str, names: list[str], choices: tuple[str, ...]) -> list[
     if unknown:
         raise ValueError(f"unknown {setting} {unknown}, choose from {list(choices)}")
 
-    return list(dict.fromkeys(names))
+    return names
 
 
 def _at_least(loglevel: str, floor: int) -> str:
diff --git a/tests/test_config.py b/tests/test_config.py
index a4386bb..54ba531 100644
--- a/tests/test_config.py
+++ b/tests/test_config.py
@@ -1,3 +1,6 @@
+import pytest
+from pydantic import ValidationError
+
 from gfmodules.logging.config import ConfigLogging
 
 
@@ -19,6 +22,16 @@ def test_an_empty_console_selection_is_kept_rather_than_read_as_the_default() ->
     assert ConfigLogging(console_streams=[]).console_streams == []
 
 
+def test_a_console_stream_named_twice_is_rejected() -> None:
+    with pytest.raises(ValidationError, match=r"duplicate console_streams \['debug'\]"):
+        ConfigLogging(console_streams=["app", "debug", "debug"])
+
+
+def test_a_syslog_stream_named_twice_is_rejected() -> None:
+    with pytest.raises(ValidationError, match=r"duplicate syslog_streams \['siem'\]"):
+        ConfigLogging(syslog_streams=["app", "siem", "siem"])
+
+
 def test_accepts_an_application_supplied_configuration() -> None:
     config = ConfigLogging(
         syslog_path="syslog:5514",
diff --git a/tests/test_config_builder.py b/tests/test_config_builder.py
index c0b902c..3be113e 100644
--- a/tests/test_config_builder.py
+++ b/tests/test_config_builder.py
@@ -263,12 +263,6 @@ def test_an_empty_selection_still_reaches_the_log_server(self) -> None:
         assert console_handlers(conf) == {}
         assert conf["loggers"]["app"]["handlers"] == ["syslog_app", "syslog_siem", "syslog_public_inspect"]
 
-    def test_a_stream_named_twice_still_gets_one_handler(self) -> None:
-        conf = build(ConfigLogging(console_streams=["debug", "debug"]))
-
-        assert list(console_handlers(conf)) == ["console_debug"]
-        assert conf["loggers"]["app"]["handlers"] == ["console_debug"]
-
 
 class TestIncludeTraces:
     def test_the_console_formatters_keep_traces_by_default(self) -> None:
@@ -381,11 +375,6 @@ def test_an_empty_selection_sends_nothing_to_the_log_server(self) -> None:
 
         assert syslog_handlers(conf) == []
 
-    def test_a_stream_named_twice_still_gets_one_handler(self) -> None:
-        conf = build(ConfigLogging(syslog_path=SYSLOG, syslog_streams=["debug", "debug"]))
-
-        assert conf["root"]["handlers"] == ["syslog_debug"]
-
 
 class TestLoggers:
     def test_uvicorn_access_is_silenced_because_the_middleware_logs_access(self) -> None: