Handle missing library in haskell_toolchain_library

haskell/private/haskell_impl.bzl

@@ -24,6 +24,8 @@ load(":private/java.bzl", "java_interop_info")
 load(":private/mode.bzl", "is_profiling_enabled")
 load(
     ":private/path_utils.bzl",
+    "get_dynamic_hs_lib_name",
+    "get_lib_name",
     "ln",
     "match_label",
     "parse_pattern",
@@ -634,18 +636,29 @@ Check that it ships with your version of GHC.
         requested_features = ctx.features,
         unsupported_features = ctx.disabled_features,
     )
+
+    # Workaround for https://github.com/tweag/rules_haskell/issues/881
+    # Static and dynamic libraries don't necessarily pair up 1 to 1.
+    # E.g. the rts package in the Unix GHC bindist contains the
+    # dynamic libHSrts and the static libCffi and libHSrts.
+    libs = {
+        get_dynamic_hs_lib_name(hs.toolchain.version, lib): {"dynamic": lib}
+        for lib in target[HaskellImportHack].dynamic_libraries
+    }
+    for lib in target[HaskellImportHack].static_libraries:
+        name = get_lib_name(lib)
+        entry = libs.get(name, {})
+        entry["static"] = lib
+        libs[name] = entry
     libraries_to_link = [
         cc_common.create_library_to_link(
             actions = ctx.actions,
             feature_configuration = feature_configuration,
-            dynamic_library = dynamic_library,
-            static_library = static_library,
+            dynamic_library = lib.get("dynamic", None),
+            static_library = lib.get("static", None),
             cc_toolchain = cc_toolchain,
         )
-        for (dynamic_library, static_library) in zip(
-            target[HaskellImportHack].dynamic_libraries,
-            target[HaskellImportHack].static_libraries,
-        )
+        for lib in libs.values()
     ]
     compilation_context = cc_common.create_compilation_context(
         headers = target[HaskellImportHack].headers,

haskell/private/path_utils.bzl

@@ -208,6 +208,23 @@ def get_lib_name(lib):
     end = paths.replace_extension(base, "") if n == -1 else base[:n]
     return end
 
+def get_dynamic_hs_lib_name(ghc_version, lib):
+    """Return name of library by dropping extension,
+    "lib" prefix, and GHC version suffix.
+
+    Args:
+      version: GHC version.
+      lib: The library File.
+
+    Returns:
+      String: name of library.
+    """
+    name = get_lib_name(lib)
+    suffix = "-ghc{}".format(ghc_version)
+    if name.endswith(suffix):
+        name = name[:-len(suffix)]
+    return name
+
 def link_libraries(libs_to_link, args):
     """Add linker flags to link against the given libraries.