CMake build: Change how third party libraries are included
- Always use dir_pw_third_party_nanopb as a path.
- Improve error messages when building Nanopb protos without
dir_pw_third_party_nanopb set.
- Specify python3 instead of python in case the build isn't run in a
Python 3 virtual environment.
Change-Id: Id8ca6f7f944348803c0275883fc7125c465235fd
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/38400
Reviewed-by: Keir Mierle <keir@google.com>
Reviewed-by: Alexei Frolov <frolv@google.com>
Pigweed-Auto-Submit: Wyatt Hepler <hepler@google.com>
Commit-Queue: Auto-Submit <auto-submit@pigweed.google.com.iam.gserviceaccount.com>
diff --git a/pw_build/docs.rst b/pw_build/docs.rst
index 96e7a37..6fff0e4 100644
--- a/pw_build/docs.rst
+++ b/pw_build/docs.rst
@@ -461,17 +461,14 @@
---------------------
The CMake build includes third-party libraries similarly to the GN build. A
``dir_pw_third_party_<library>`` cache variable is defined for each third-party
-dependency. This variable can have one of three values:
+dependency. The variable must be set to the absolute path of the library in
+order to use it. If the variable is empty
+(``if("${dir_pw_third_party_<library>}" STREQUAL "")``), the dependency is not
+available.
-* ``""`` (empty) -- the dependency is not available
-* ``PRESENT`` -- the dependency is available and is already included in the
- build
-* ``</path/to/the/dependency>`` -- the dependency is available and will be
- automatically imported from this path using ``add_subdirectory``.
-
-If the variable is empty (``if("${dir_pw_third_party_<library>}" STREQUAL
-"")``), the dependency is not available. Otherwise, it is available and
-libraries declared by it can be referenced.
+Third-party dependencies are not automatically added to the build. They can be
+manually added with ``add_subdirectory`` or by setting the
+``pw_third_party_<library>_ADD_SUBDIRECTORY`` option to ``ON``.
Third party variables are set like any other cache global variable in CMake. It
is recommended to set these in one of the following ways:
@@ -481,7 +478,7 @@
.. code-block:: cmake
- set(dir_pw_third_party_nanopb PRESENT CACHE STRING "" FORCE)
+ set(dir_pw_third_party_nanopb ${CMAKE_CURRENT_SOURCE_DIR}/external/nanopb CACHE PATH "" FORCE)
* Set the variable at the command line with the ``-D`` option.