Factor out uses of darwin_convert_to_dylibs

Addressing PR review comments.

Reducing the risk of future refactorings introducing subtle bugs by
missing required steps in get_solibs_for_ghc_linker.

haskell/doctest.bzl

@@ -5,11 +5,10 @@ load("@bazel_skylib//lib:paths.bzl", "paths")
 load(":private/context.bzl", "haskell_context")
 load(
     ":private/path_utils.bzl",
-    "darwin_convert_to_dylibs",
     "get_lib_name",
     "make_path",
 )
-load(":private/providers.bzl", "get_mangled_libs")
+load(":private/providers.bzl", "get_mangled_libs", "get_solibs_for_ghc_linker")
 load(":private/set.bzl", "set")
 load(
     "@io_tweag_rules_haskell//haskell:private/providers.bzl",
@@ -132,16 +131,7 @@ def _haskell_doctest_single(target, ctx):
                 ])
 
     # Transitive library dependencies for runtime.
-    trans_link_ctx = build_info.transitive_cc_dependencies.dynamic_linking
-    trans_libs = get_mangled_libs(trans_link_ctx.libraries_to_link.to_list())
-    trans_import_libs = set.to_list(build_info.transitive_import_dependencies)
-
-    _library_deps = trans_libs + trans_import_libs
-    if hs.toolchain.is_darwin:
-        # GHC's builtin linker requires .dylib files on MacOS.
-        library_deps = darwin_convert_to_dylibs(hs, _library_deps)
-    else:
-        library_deps = _library_deps
+    library_deps = get_solibs_for_ghc_linker(hs, build_info)
     ld_library_path = make_path(library_deps)
 
     header_files = lib_info.header_files if lib_info != None else bin_info.header_files

haskell/lint.bzl

@@ -11,10 +11,9 @@ load(":private/context.bzl", "haskell_context")
 load(":private/packages.bzl", "expose_packages")
 load(
     ":private/path_utils.bzl",
-    "darwin_convert_to_dylibs",
     "target_unique_name",
 )
-load(":private/providers.bzl", "get_mangled_libs")
+load(":private/providers.bzl", "get_solibs_for_ghc_linker")
 load(":private/set.bzl", "set")
 
 def _collect_lint_logs(deps):
@@ -75,16 +74,7 @@ def _haskell_lint_aspect_impl(target, ctx):
     )
 
     # Transitive library dependencies for runtime.
-    trans_link_ctx = build_info.transitive_cc_dependencies.dynamic_linking
-    trans_libs = get_mangled_libs(trans_link_ctx.libraries_to_link.to_list())
-    trans_import_libs = set.to_list(build_info.transitive_import_dependencies)
-
-    _library_deps = trans_libs + trans_import_libs
-    if hs.toolchain.is_darwin:
-        # GHC's builtin linker requires .dylib files on MacOS.
-        library_deps = darwin_convert_to_dylibs(hs, _library_deps)
-    else:
-        library_deps = _library_deps
+    library_deps = get_solibs_for_ghc_linker(hs, build_info)
 
     ctx.actions.run_shell(
         inputs = depset(transitive = [

haskell/private/actions/compile.bzl

@@ -9,13 +9,12 @@ load(
 )
 load(
     ":private/path_utils.bzl",
-    "darwin_convert_to_dylibs",
     "declare_compiled",
     "make_path",
     "target_unique_name",
 )
 load(":private/pkg_id.bzl", "pkg_id")
-load(":private/providers.bzl", "get_mangled_libs")
+load(":private/providers.bzl", "get_solibs_for_ghc_linker")
 load(":private/set.bzl", "set")
 
 def _process_hsc_file(hs, cc, hsc_flags, hsc_file):
@@ -238,16 +237,7 @@ def _compilation_defaults(hs, cc, java, dep_info, srcs, import_dir_map, extra_sr
         args.add(f)
 
     # Transitive library dependencies for runtime.
-    trans_link_ctx = dep_info.transitive_cc_dependencies.dynamic_linking
-    trans_libs = get_mangled_libs(trans_link_ctx.libraries_to_link.to_list())
-    trans_import_libs = set.to_list(dep_info.transitive_import_dependencies)
-
-    _library_deps = trans_libs + trans_import_libs
-    if hs.toolchain.is_darwin:
-        # GHC's builtin linker requires .dylib files on MacOS.
-        library_deps = darwin_convert_to_dylibs(hs, _library_deps)
-    else:
-        library_deps = _library_deps
+    library_deps = get_solibs_for_ghc_linker(hs, dep_info)
     ld_library_path = make_path(library_deps)
 
     return DefaultCompileInfo(

haskell/private/actions/repl.bzl

@@ -3,14 +3,13 @@
 load(":private/packages.bzl", "expose_packages")
 load(
     ":private/path_utils.bzl",
-    "darwin_convert_to_dylibs",
     "get_lib_name",
     "is_shared_library",
     "ln",
     "make_path",
     "target_unique_name",
 )
-load(":private/providers.bzl", "get_mangled_libs")
+load(":private/providers.bzl", "get_solibs_for_ghc_linker")
 load(
     ":private/set.bzl",
     "set",
@@ -76,16 +75,7 @@ def build_haskell_repl(
             args += ["-l{0}".format(lib_name)]
 
     # Transitive library dependencies to have in runfiles.
-    trans_link_ctx = build_info.transitive_cc_dependencies.dynamic_linking
-    trans_libs = get_mangled_libs(trans_link_ctx.libraries_to_link.to_list())
-    trans_import_libs = set.to_list(build_info.transitive_import_dependencies)
-
-    _library_deps = trans_libs + trans_import_libs
-    if hs.toolchain.is_darwin:
-        # GHC's builtin linker requires .dylib files on MacOS.
-        library_deps = darwin_convert_to_dylibs(hs, _library_deps)
-    else:
-        library_deps = _library_deps
+    library_deps = get_solibs_for_ghc_linker(hs, build_info)
     ld_library_path = make_path(
         library_deps,
         prefix = "$RULES_HASKELL_EXEC_ROOT",

haskell/private/providers.bzl

@@ -1,3 +1,6 @@
+load(":private/path_utils.bzl", "darwin_convert_to_dylibs")
+load(":private/set.bzl", "set")
+
 DefaultCompileInfo = provider(
     doc = "Default compilation files and configuration.",
     fields = {
@@ -109,6 +112,37 @@ def get_mangled_libs(ext_libs):
     """Just a dumb helper because skylark doesn’t do lambdas."""
     return [ext_lib.mangled_lib for ext_lib in ext_libs]
 
+def get_solibs_for_ghc_linker(hs, build_info):
+    """Return all C library dependencies for GHC's linker.
+
+    GHC has it's own builtin linker. It is used for Template Haskell, for GHCi,
+    during doctests, etc. GHC's linker differs from the system's dynamic linker
+    in some ways. E.g. it strictly assumes that dynamic libraries end on .dylib
+    on MacOS.
+
+    This function returns a list of all transitive C library dependencies
+    (static or dynamic), taking the requirements of GHC's linker into account.
+
+    Args:
+      hs: Haskell context.
+      build_info: HaskellBinaryInfo provider.
+
+    Returns:
+      List of library files suitable for GHC's builtin linker.
+    """
+    trans_link_ctx = build_info.transitive_cc_dependencies.dynamic_linking
+    trans_libs = get_mangled_libs(trans_link_ctx.libraries_to_link.to_list())
+    trans_import_libs = set.to_list(build_info.transitive_import_dependencies)
+
+    _library_deps = trans_libs + trans_import_libs
+    if hs.toolchain.is_darwin:
+        # GHC's builtin linker requires .dylib files on MacOS.
+        library_deps = darwin_convert_to_dylibs(hs, _library_deps)
+    else:
+        library_deps = _library_deps
+
+    return library_deps
+
 HaskellLibraryInfo = provider(
     doc = "Library-specific information.",
     fields = {