Separate the dependency list ( requirements) from conanfile.py - c++

Question

We are planning to set up conan repositories for our C++ codes. We want to expose only the list of dependencies ( lib/version#user/channel) to the developers, not the logic we put in conanfile.py We are planning so, because we are creating a wrapper around conan which will have several logic and checks. This wrapper will be exposed to the users. They do not need to know the detailed logic and build steps.
Is there a way to implement the requirements ( dependency list ) outside conanfile.py, and make the list available to the users, so that they can choose which version of the library they want to use - something similar ( not same, though ) to pom.xml in maven world ?

Answer 1

The above answer from #amit-jaim is quite good. I would like to point a couple of further details:
It is necessary to exports the .list file, as it will be also used when the conanfile is used in the cache
The conanfile can be made a bit more pythonic
The code could be like:
from conans import ConanFile, load
class HelloConan(ConanFile):
name = "Hello"
version = "0.1"
exports = "deps.list"
def requirements(self):
for r in load("deps.list").splitlines():
self.requires(r)
If you want to be able to run conan create from directories other than the current conanfile then getting the current location of the conanfile would be necessary, something like:
def requirements(self):
f = os.path.join(os.path.dirname(__file__), "deps.list")
for r in load(f).splitlines():
self.requires(r)

Answer 2

I found 2 solutions :
Create a list of libraries to be used and then read that from requirements method :
localhost$ cat dependencies.list
lib1/0.0.1#user/stable
lib2/1.6.0#user/stable
lib3/1.5.0#suer/stable
Remember, there should not be any quote around the values, in the way we pass them to the self.requires() method. Now define the requirements method in conanfile.py in the following way :
def requirements(self):
try:
with open("/path/to/dependencies.list") as c:
line=c.readline()
while line:
self.requires(line)
line=c.readline()
except Exception as ex:
print(ex)
Define requirements method outside conanfile.py. Use this method if library dependency is conditional.
localhost$ cat requires.py
def requires(self):
self.requires("lib1/0.0.1#user/stable")
self.requires("lib2/2.6.0#user/stable")
if self.options.shared:
self.requires("lib3/1.5.0#user/stable")
else:
self.requires("lib3/1.5.1#user/stable")`
Then import the requires method and assign that to the requirements method in conan class, in the following way :
from conans import ConanFile, CMake, tools
from requires import requires
class HelloConan(ConanFile):
name = Hello
version = "0.0.1"
license = "LICENSE"
url = "URL"
description = "libHello, Version 0.0.1"
settings = "os", "compiler", "build_type", "arch"
....
....
Now instead of defining the requirements method with def requirements(self), do this :
requirements=requires
....
....
That's it !! conan install will get the library details, and if found in the registry, those will be installed !!