Add ASGI scope access-log atoms

docs/how_to_guides/logging.rst

@@ -66,8 +66,14 @@ p            process ID
 {Header}i    request header
 {Header}o    response header
 {Variable}e  environment variable
+{Variable}s  string or byte value from the ASGI scope
 ===========  ===========
 
+For example, ``%({myapp.trace_id}s)s`` logs a trace ID added to the
+request's ASGI scope by the application. Byte values are decoded as
+Latin-1; other value types and missing keys appear as ``-``. The
+``{Variable}e`` atom continues to read process environment variables.
+
 Customising the logger
 ----------------------
 

src/hypercorn/logging.py

@@ -140,6 +140,11 @@ def __init__(
             self[f"{{{name.decode('latin1').lower()}}}i"] = value.decode("latin1")
         for name, value in os.environ.items():
             self[f"{{{name.lower()}}}e"] = value
+        for name, value in request.items():
+            if isinstance(value, str):
+                self[f"{{{name.lower()}}}s"] = value
+            elif isinstance(value, bytes):
+                self[f"{{{name.lower()}}}s"] = value.decode("latin1")
         protocol = request.get("http_version", "ws")
         client = request.get("client")
         if client is None:

tests/test_logging.py

@@ -3,6 +3,7 @@
 import logging
 import os
 import time
+from typing import cast
 
 import pytest
 
@@ -110,6 +111,29 @@ def test_access_log_environ_atoms(http_scope: HTTPScope, response: ResponseSumma
     assert atoms["{random}e"] == "Environ"
 
 
+def test_access_log_scope_atoms(
+    http_scope: HTTPScope, response: ResponseSummary, monkeypatch: pytest.MonkeyPatch
+) -> None:
+    monkeypatch.setenv("MYAPP_TRACE_ID", "process-value")
+    scope = cast(
+        HTTPScope,
+        {
+            **http_scope,
+            "myapp_trace_id": "request-value",
+            "myapp_bytes": b"binary-\xff",
+            "myapp_object": object(),
+        },
+    )
+
+    atoms = AccessLogAtoms(scope, response, 0)
+
+    assert atoms["{MYAPP_TRACE_ID}s"] == "request-value"
+    assert "%({myapp_trace_id}s)s" % atoms == "request-value"
+    assert atoms["{myapp_bytes}s"] == "binary-\xff"
+    assert atoms["{myapp_object}s"] == "-"
+    assert atoms["{myapp_trace_id}e"] == "process-value"
+
+
 def test_nonstandard_status_code(http_scope: HTTPScope) -> None:
     atoms = AccessLogAtoms(http_scope, {"status": 441, "headers": []}, 0)
     assert atoms["st"] == "<???441???>"