Merge pull request #70 from astrofrog/deprecate-absolute

Add back support for absolute source paths but deprecate it

extension_helpers/_setup_helpers.py

@@ -104,6 +104,37 @@ def get_extensions(srcdir="."):
         )
         ext_modules.append(ext)
 
+    # Since https://github.com/astropy/extension-helpers/pull/67,
+    # extensions that used absolute paths in source names stopped working.
+    # Absolute paths in source paths are undesirable but we need to
+    # preserve backward-compatibility until we bump the major release,
+    # so we check for the case of absolute paths and emit a deprecation
+    # warning for now.
+    for extension in ext_modules:
+        sources = []
+        fixed = []
+        for source in extension.sources:
+            if os.path.isabs(source):
+                try:
+                    source = os.path.relpath(source)
+                except ValueError:
+                    # In some cases it's impossible to use a relative path, for
+                    # instance if the source files are on a different drive. In
+                    # this case there's not much we can do so we just proceed.
+                    pass
+                fixed.append(source)
+            sources.append(source)
+        if fixed:
+            log.warning(
+                "Extension {} contains source files "
+                "({}) that are specified using an absolute "
+                "path, which will not be supported in future.".format(
+                    extension.name, ", ".join(fixed)
+                )
+            )
+
+        extension.sources = sources
+
     return ext_modules