Don't use symbolic links to expose runghc (fails on windows)

haskell/cabal.bzl

@@ -531,7 +531,7 @@ def _haskell_cabal_library_impl(ctx):
         arguments = [json_args.path],
         inputs = depset([json_args], transitive = [c.inputs]),
         input_manifests = c.input_manifests,
-        tools = [c.cabal_wrapper],
+        tools = [c.cabal_wrapper, ctx.executable._runghc],
         outputs = outputs,
         env = c.env,
         mnemonic = "HaskellCabalLibrary",
@@ -814,7 +814,7 @@ def _haskell_cabal_binary_impl(ctx):
             binary,
             data_dir,
         ],
-        tools = [c.cabal_wrapper],
+        tools = [c.cabal_wrapper, ctx.executable._runghc],
         env = c.env,
         mnemonic = "HaskellCabalBinary",
         progress_message = "HaskellCabalBinary {}".format(hs.label),

haskell/private/runghc.bzl

@@ -7,32 +7,60 @@ load("@bazel_skylib//lib:paths.bzl", "paths")
 # platform. In order to achieve this, we provide a runghc of a
 # toolchain targeting the execution platform.
 #
-# Producing runghc with a custom rule, as defined here, allows to use
-# it in rules which are using a Haskell toolchain for the target
-# platform.
+# Producing a runghc wrapper with a custom rule, as defined here,
+# allows to use it in rules which are using a Haskell toolchain for
+# the target platform.
 #
 
-def _runghc_impl(ctx):
+def _runghc_wrapper_impl(ctx):
     hs_toolchain = ctx.toolchains["@rules_haskell//haskell:toolchain"]
-    (_, extension) = paths.split_extension(hs_toolchain.tools.runghc.path)
 
-    runghc_file = ctx.actions.declare_file(ctx.label.name + extension)
-    ctx.actions.symlink(
-        output = runghc_file,
-        target_file = hs_toolchain.tools.runghc,
+    f = hs_toolchain.tools.runghc
+    runghc_runfile_path = paths.join(f.owner.workspace_name, f.owner.package, f.owner.name)
+    runghc_wrapper_file = ctx.actions.declare_file(ctx.label.name)
+    ctx.actions.write(
+        output = runghc_wrapper_file,
+        content = """\
+#!/usr/bin/env bash
+
+# --- begin runfiles.bash initialization v2 ---
+# Copy-pasted from the Bazel Bash runfiles library v2.
+set -uo pipefail; f=bazel_tools/tools/bash/runfiles/runfiles.bash
+source "${{RUNFILES_DIR:-/dev/null}}/$f" 2>/dev/null || \
+source "$(grep -sm1 "^$f " "${{RUNFILES_MANIFEST_FILE:-/dev/null}}" | cut -f2- -d' ')" 2>/dev/null || \
+source "$0.runfiles/$f" 2>/dev/null || \
+source "$(grep -sm1 "^$f " "$0.runfiles_manifest" | cut -f2- -d' ')" 2>/dev/null || \
+source "$(grep -sm1 "^$f " "$0.exe.runfiles_manifest" | cut -f2- -d' ')" 2>/dev/null || \
+{{ echo>&2 "ERROR: cannot find $f"; exit 1; }}; f=; set -e
+# --- end runfiles.bash initialization v2 ---
+
+$(rlocation "{runghc}") "$@"
+""".format(runghc = runghc_runfile_path),
         is_executable = True,
     )
 
     return [DefaultInfo(
-        executable = runghc_file,
+        executable = runghc_wrapper_file,
         runfiles = hs_toolchain.cc_wrapper.runfiles.merge(
-            ctx.runfiles(files = [runghc_file, hs_toolchain.tools.runghc]),
+            ctx.runfiles(files = [runghc_wrapper_file, hs_toolchain.tools.runghc]),
         ),
     )]
 
-runghc = rule(
+_runghc_wrapper = rule(
     executable = True,
-    implementation = _runghc_impl,
+    implementation = _runghc_wrapper_impl,
     toolchains = ["@rules_haskell//haskell:toolchain"],
-    doc = """Produces the runghc program.""",
+    doc = """Produces the runghc wrapper script.""",
 )
+
+def runghc(name, visibility):
+    _runghc_wrapper(name = name + ".sh")
+    native.sh_binary(
+        name = name,
+        srcs = [name + ".sh"],
+        data = [name + ".sh"],
+        deps = [
+            "@bazel_tools//tools/bash/runfiles",
+        ],
+        visibility = visibility,
+    )