fix cppstd compat (#16346)

conans/client/graph/compatibility.py

@@ -41,8 +41,8 @@ def cppstd_compat(conanfile):
         cppstd_possible_values = supported_cppstd(conanfile)
         if cppstd_possible_values is None:
             conanfile.output.warning(f'No cppstd compatibility defined for compiler "{compiler}"')
-        else:
-            factors.append([{"compiler.cppstd": v} for v in cppstd_possible_values if v != cppstd])
+        else: # The current cppst must be included in case there is other factor
+            factors.append([{"compiler.cppstd": v} for v in cppstd_possible_values])
 
     if compiler == "msvc":
         msvc_fallback = {"194": "193"}.get(compiler_version)

conans/test/integration/package_id/test_cache_compatibles.py

@@ -398,6 +398,13 @@ def test_msvc_194_fallback(self):
         assert "mylib/1.0: Main binary package 'e340edd75790e7156c595edebd3d98b10a2e091e' missing."\
                f"Using compatible package '{package_id1}'"
 
+        c.run("install --requires=mylib/1.0@ -s os=Windows -s arch=x86_64 -s build_type=Release "
+              "-s compiler=msvc "
+              "-s compiler.version=194 -s compiler.cppstd=17 "
+              "-s compiler.runtime=dynamic -pr:b=profile_build")
+        assert "mylib/1.0: Main binary package 'e340edd75790e7156c595edebd3d98b10a2e091e' missing." \
+               f"Using compatible package '{package_id1}'"
+
 
 class TestErrorsCompatibility:
     """ when the plugin fails, we want a clear message and a helpful trace