Conan-Package: Getting compiled files from other Conan-Packages

Question

I'm using Conan as a dependency manager for C++ and I want to create a package which requires a compiled file from another, already created, Conan-package. I'm currently trying to create a package for the OpenStreetMap-Library OSM-binary (https://github.com/scrosby/OSM-binary.git).

The Makefile for this project (which can be found at ./OSM-binary/src/Makefile) requires a file called protoc from the protobuf-project (https://github.com/google/protobuf). This protoc-file can be found after compiling the protobuf-project in ./protobuf/src.

Without this file compiling the OSM-sources will fail with an error: make: ../protoc: Command not found

The Problem

As conan's documentation suggests to copy my needed files to folders in my package, e.g header-files to ./include, libs to ./lib, etc. According to this, after building the protobuf-project via make, I'm copying the mentioned file via

def package(self):
    self.copy("*.so", dst="lib", keep_path=False)
    self.copy("protoc", dst="scripts", src="./protobuf/src")

to an folder called "scripts".

But at this point the black magic starts. My first question is, how can I access any of these packed files (e. g. the *.so files or any other files (here the protoc-file) which are present in an package) from another package? For me, even after reading conan's documentation, it's not clear how conan stores it's packed files and how to access these or any other files packed in the previous step.

Now back at the OSM-Project my approach would be setting the correct path manually in the Makefile via the tools.replace command. First I declared the protobuf-packaged as an requirement

requires = "protobuf/2.5.0@test/testing"

and replaced the corresponding lines (in version 1.3.3, line 7) in the osm-Makefile with the correct path to the protoc-file.

tools.replace_in_file("OSM-binary/src/Makefile",
                      "PROTOC   ?= protoc",
                      "PROTOC   ?= <path-to-file>/protoc")

Now this leads us to my actual question: How do I get the path to the protoc-file which can be found in the protobuf-package in a folder called scripts, or is there any other way to do it?

Thanks, Chris

drodri drodri · Accepted Answer · 2018-07-24T09:20:12

There are different ways to access files from your dependencies:

If you want to directly run some file from your dependencies, you could use the self.run(...., run_environment=True), that will automatically set the PATH, LD_LIBRARY_PATH, etc so the binaries are found in the place where the package is installed. Find more information here
You can directly import the files you want from your dependencies, doing a copy (which is done before the build() method) of such files into the build folder, so they can be directly used there. The path you can use in your script is the current one, or self.build_folder. The imported files will be automatically removed after build, so they are not accidentally repackaged. Check imports docs
You can obtain information from your dependencies from the self.deps_cpp_info attribute. Check the reference here. That means you can get the paths to your protobuf dependency with something like

def build(self):
   # Get the directory where protobuf package is installed
   protoc_root = self.deps_cpp_info["protobuf"].rootpath
   # Note this is a list
   protoc_bin_paths = self.deps_cpp_info["protobuf"].bin_paths

Conan-Package: Getting compiled files from other Conan-Packages

1 Answers