From af69745110cab1bf19543831449fc4de53593e3c Mon Sep 17 00:00:00 2001
From: Christophe Bedard <fixed-term.christophe.bourquebedard@de.bosch.com>
Date: Fri, 16 Aug 2019 12:00:37 +0200
Subject: [PATCH] Extract empty lttng interface functions to another file

---
 .../tracetools_trace/tools/lttng.py           | 34 +++++--------------
 .../tracetools_trace/tools/lttng_impl.py      | 10 +++---
 .../tracetools_trace/tools/lttng_stub.py      | 31 +++++++++++++++++
 3 files changed, 45 insertions(+), 30 deletions(-)
 create mode 100644 tracetools_trace/tracetools_trace/tools/lttng_stub.py

diff --git a/tracetools_trace/tracetools_trace/tools/lttng.py b/tracetools_trace/tracetools_trace/tools/lttng.py
index cfe20e1..de22fd5 100644
--- a/tracetools_trace/tracetools_trace/tools/lttng.py
+++ b/tracetools_trace/tracetools_trace/tools/lttng.py
@@ -17,26 +17,14 @@
 from typing import List
 
 try:
-    import lttng
+    from . import lttng_impl
 
-    from .lttng_impl import _lttng_destroy
-    from .lttng_impl import _lttng_setup
-    from .lttng_impl import _lttng_start
-    from .lttng_impl import _lttng_stop
+    _lttng = lttng_impl
 except ImportError:
-    lttng = None
+    # Fall back on empty functions
+    from . import lttng_stub
 
-    def _lttng_destroy(*args, **kwargs) -> None:
-        pass
-
-    def _lttng_setup(*args, **kwargs) -> None:
-        pass
-
-    def _lttng_start(*args, **kwargs) -> None:
-        pass
-
-    def _lttng_stop(*args, **kwargs) -> None:
-        pass
+    _lttng = lttng_stub
 
 from .names import DEFAULT_CONTEXT
 from .names import DEFAULT_EVENTS_KERNEL
@@ -60,10 +48,8 @@ def lttng_init(
     :param kernel_events: list of kernel events to enable
     :param context_names: list of context elements to enable
     """
-    if lttng is None:
-        return None
-    _lttng_setup(session_name, base_path, ros_events, kernel_events, context_names)
-    _lttng_start(session_name)
+    _lttng.setup(session_name, base_path, ros_events, kernel_events, context_names)
+    _lttng.start(session_name)
 
 
 def lttng_fini(session_name: str) -> None:
@@ -72,7 +58,5 @@ def lttng_fini(session_name: str) -> None:
 
     :param session_name: the name of the session
     """
-    if lttng is None:
-        return None
-    _lttng_stop(session_name)
-    _lttng_destroy(session_name)
+    _lttng.stop(session_name)
+    _lttng.destroy(session_name)
diff --git a/tracetools_trace/tracetools_trace/tools/lttng_impl.py b/tracetools_trace/tracetools_trace/tools/lttng_impl.py
index d3a64e5..c47ed1b 100644
--- a/tracetools_trace/tracetools_trace/tools/lttng_impl.py
+++ b/tracetools_trace/tracetools_trace/tools/lttng_impl.py
@@ -25,7 +25,7 @@ from .path import DEFAULT_BASE_PATH
 from .path import get_full_session_path
 
 
-def _lttng_setup(
+def setup(
     session_name: str,
     base_path: str = DEFAULT_BASE_PATH,
     ros_events: List[str] = DEFAULT_EVENTS_ROS,
@@ -113,7 +113,7 @@ def _lttng_setup(
     _add_context(enabled_handles, context_list)
 
 
-def _lttng_start(session_name: str) -> None:
+def start(session_name: str) -> None:
     """
     Start LTTng session, and check for errors.
 
@@ -124,7 +124,7 @@ def _lttng_start(session_name: str) -> None:
         raise RuntimeError(f'failed to start tracing: {lttng.strerror(result)}')
 
 
-def _lttng_stop(session_name: str) -> None:
+def stop(session_name: str) -> None:
     """
     Stop LTTng session, and check for errors.
 
@@ -135,7 +135,7 @@ def _lttng_stop(session_name: str) -> None:
         raise RuntimeError(f'failed to stop tracing: {lttng.strerror(result)}')
 
 
-def _lttng_destroy(session_name: str) -> None:
+def destroy(session_name: str) -> None:
     """
     Destroy LTTng session, and check for errors.
 
@@ -175,7 +175,7 @@ def _create_session(session_name: str, full_path: str) -> None:
     if result == -LTTNG_ERR_EXIST_SESS:
         # Sessions seem to persist, so if it already exists,
         # just destroy it and try again
-        _lttng_destroy(session_name)
+        destroy(session_name)
         result = lttng.create(session_name, full_path)
     if result < 0:
         raise RuntimeError(f'session creation failed: {lttng.strerror(result)}')
diff --git a/tracetools_trace/tracetools_trace/tools/lttng_stub.py b/tracetools_trace/tracetools_trace/tools/lttng_stub.py
new file mode 100644
index 0000000..47c0c63
--- /dev/null
+++ b/tracetools_trace/tracetools_trace/tools/lttng_stub.py
@@ -0,0 +1,31 @@
+# Copyright 2019 Robert Bosch GmbH
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Stub version of the interface for tracing with LTTng."""
+
+
+def setup(*args, **kwargs) -> None:
+    pass
+
+
+def start(*args, **kwargs) -> None:
+    pass
+
+
+def stop(*args, **kwargs) -> None:
+    pass
+
+
+def destroy(*args, **kwargs) -> None:
+    pass