[infrastructure] Add compatibility rule in order to consume packages from Conan Center

.github/conan/compatibility.py

@@ -0,0 +1,77 @@
+from conan.tools.build import supported_cppstd, supported_cstd
+
+
+def cppstd_compat(conanfile):
+    """Compute compatibility factors for different cppstd and cstd versions.
+       By default, different compiler.cppstd and compiler.cstd are compatible.
+       Returns a list of lists of dicts, each sublist is a potential factor with different settings.
+    """
+    extension_properties = getattr(conanfile, "extension_properties", {})
+    compiler = conanfile.settings.get_safe("compiler")
+    compiler_version = conanfile.settings.get_safe("compiler.version")
+    cppstd = conanfile.settings.get_safe("compiler.cppstd")
+    if not compiler or not compiler_version:
+        return []
+    factors = []  # List of list, each sublist is a potential combination
+    if cppstd is not None and extension_properties.get("compatibility_cppstd") is not False:
+        cppstd_possible_values = supported_cppstd(conanfile)
+        if cppstd_possible_values is None:
+            conanfile.output.warning(f'No cppstd compatibility defined for compiler "{compiler}"')
+        else: # The current cppst must be included in case there is other factor
+            factors.append([{"compiler.cppstd": v} for v in cppstd_possible_values])
+
+    cstd = conanfile.settings.get_safe("compiler.cstd")
+    if cstd is not None and extension_properties.get("compatibility_cstd") is not False:
+        cstd_possible_values = supported_cstd(conanfile)
+        if cstd_possible_values is None:
+            conanfile.output.warning(f'No cstd compatibility defined for compiler "{compiler}"')
+        else:
+            factors.append([{"compiler.cstd": v} for v in cstd_possible_values if v != cstd])
+    return factors
+
+
+def compatibility(conanfile):
+    """Compute all compatibility settings combinations for a given conanfile.
+       Returns a list of dicts with "settings" key containing a list of (key, value) tuples.
+    """
+    factors = cppstd_compat(conanfile)
+
+    # MSVC 194->193 fallback compatibility
+    compiler = conanfile.settings.get_safe("compiler")
+    compiler_version = conanfile.settings.get_safe("compiler.version")
+    if compiler == "msvc":
+        msvc_fallback = {"194": "193"}.get(compiler_version)
+        if msvc_fallback:
+            factors.append([{"compiler.version": msvc_fallback}])
+
+    # Apple Clang 17->13 fallback compatibility
+    if compiler == "apple-clang" and compiler_version == "17":
+        factors.append([{"compiler.version": "13"}])
+
+    # Linux GCC 13->11 fallback compatibility
+    if compiler == "gcc" and compiler_version == "13":
+        factors.append([{"compiler.version": "11"}])
+
+    # Combine factors to compute all possible configurations
+    combinations = _factors_combinations(factors)
+    # Final compatibility settings combinations to check
+    return [{"settings": [(k, v) for k, v in comb.items()]} for comb in combinations]
+
+
+def _factors_combinations(factors):
+    """Given a list of factors (each factor is a list of dicts), compute all combinations.
+       Returns a list of dicts with all combinations of the input factors.
+    """
+    combinations = []
+    for factor in factors:
+        if not combinations:
+            combinations = factor
+            continue
+        new_combinations = []
+        for comb in combinations:
+            for f in factor:
+                new_comb = comb.copy()
+                new_comb.update(f)
+                new_combinations.append(new_comb)
+        combinations.extend(new_combinations)
+    return combinations

.github/workflows/ci.yml

@@ -51,6 +51,9 @@ jobs:
           pip install meson
           conan --version
           conan profile detect --force
+          conan_home=$(conan config home)
+          mkdir -p "${conan_home}/extensions/plugins/compatibility"
+          cp "${GITHUB_WORKSPACE}/.github/conan/compatibility.py" "${conan_home}/extensions/plugins/compatibility/compatibility.py"
 
       - name: Find and run examples
         shell: bash