Add silent replace option to linker.add_lib_flags

source/fab/tools/linker.py

@@ -10,6 +10,7 @@
 import os
 from pathlib import Path
 from typing import cast, Dict, List, Optional
+import warnings
 
 from fab.tools.category import Category
 from fab.tools.compiler import Compiler
@@ -83,12 +84,20 @@ def get_lib_flags(self, lib: str) -> List[str]:
         except KeyError:
             raise RuntimeError(f"Unknown library name: '{lib}'")
 
-    def add_lib_flags(self, lib: str, flags: List[str]):
+    def add_lib_flags(self, lib: str, flags: List[str],
+                      silent_replace: bool = False):
         '''Add a set of flags for a standard library
 
         :param lib: the library name
         :param flags: the flags to use with the library
+        :param silent_replace: if set, no warning will be printed when an
+            existing lib is overwritten.
         '''
+        if lib in self._lib_flags and not silent_replace:
+            warnings.warn(f"Replacing existing flags for library {lib}: "
+                          f"'{self._lib_flags[lib]}' with "
+                          f"'{flags}'.")
+
         # Make a copy to avoid modifying the caller's list
         self._lib_flags[lib] = flags[:]
 

tests/unit_tests/tools/test_linker.py

@@ -9,6 +9,7 @@
 
 from pathlib import Path
 from unittest import mock
+import warnings
 
 import pytest
 
@@ -115,7 +116,7 @@ def test_linker_add_lib_flags(mock_c_compiler):
     assert result == ["-L", "xios/lib", "-I", "xios/inc"]
 
 
-def test_linker_add_lib_flags_overwrite(mock_c_compiler):
+def test_linker_add_lib_flags_overwrite_defaults(mock_c_compiler):
     """Linker should provide a way to replace the default flags for a library"""
     linker = Linker(compiler=mock_c_compiler)
 
@@ -124,13 +125,35 @@ def test_linker_add_lib_flags_overwrite(mock_c_compiler):
     assert result == ["$(nf-config --flibs)", "($nc-config --libs)"]
 
     # Replace them with another set of flags.
-    linker.add_lib_flags("netcdf", ["-L", "netcdf/lib", "-I", "netcdf/inc"])
+    warn_message = 'Replacing existing flags for library netcdf'
+    with pytest.warns(UserWarning, match=warn_message):
+        linker.add_lib_flags("netcdf", ["-L", "netcdf/lib", "-I", "netcdf/inc"])
 
     # Test that we can see our custom flags
     result = linker.get_lib_flags("netcdf")
     assert result == ["-L", "netcdf/lib", "-I", "netcdf/inc"]
 
 
+def test_linker_add_lib_flags_overwrite_silent(mock_c_compiler):
+    """Linker should provide the option to replace flags for a library without
+    generating a warning
+    """
+    linker = Linker(compiler=mock_c_compiler)
+
+    # Initially we have the default netcdf flags
+    linker.add_lib_flags("customlib", ["-q", "/tmp", "-j"])
+    assert linker.get_lib_flags("customlib") == ["-q", "/tmp", "-j"]
+
+    # Replace them with another set of flags.
+    with warnings.catch_warnings():
+        warnings.simplefilter("error")
+        linker.add_lib_flags("customlib", ["-t", "-b"], silent_replace=True)
+
+    # Test that we can see our custom flags
+    result = linker.get_lib_flags("customlib")
+    assert result == ["-t", "-b"]
+
+
 def test_linker_remove_lib_flags(mock_c_compiler):
     """Linker should provide a way to remove the flags for a library"""
     linker = Linker(compiler=mock_c_compiler)