Handling of toolchain libraries in stack_snapshot

CHANGELOG.md

@@ -8,6 +8,14 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/).
 
 [Unreleased]: https://github.com/tweag/rules_haskell/compare/v0.14...master
 
+### Changed
+
+* By default, the `stack_snapshot` rule now relies on stack to determine toolchain libraries.
+This can be a breaking change on windows if we rely on a stack snapshot containing `Win32 <= 2.13.2.0`,
+as we encounter [this issue](https://github.com/haskell/win32/issues/193).
+In this case, to ensure the toolchain `Win32` library is used (instead of trying to compile a new one),
+it can be droped from a custom stack snapshot as in the [./stackage_snapshot.yaml](./stackage_snapshot.yaml) file.
+
 ## [0.14.0] 2021-12-21
 
 [0.14.0]: https://github.com/tweag/rules_haskell/compare/v0.13...v0.14

WORKSPACE

@@ -40,7 +40,6 @@ load(
     "@rules_haskell//:constants.bzl",
     "test_asterius_version",
     "test_ghc_version",
-    "test_stack_snapshot",
 )
 load("@rules_haskell//haskell:cabal.bzl", "stack_snapshot")
 
@@ -53,6 +52,7 @@ stack_snapshot(
             "exe",
         ],
     },
+    local_snapshot = "//:stackage_snapshot.yaml",
     packages = [
         # Core libraries
         "array",
@@ -90,7 +90,6 @@ stack_snapshot(
         "temporary",
     ],
     setup_deps = {"polysemy": ["cabal-doctest"]},
-    snapshot = test_stack_snapshot,
     stack_snapshot_json = "//:stackage_snapshot.json" if not is_windows else None,
     tools = [
         # This is not required, as `stack_snapshot` would build alex
@@ -108,8 +107,8 @@ stack_snapshot(
 stack_snapshot(
     name = "stackage-zlib",
     extra_deps = {"zlib": ["//tests:zlib"]},
+    local_snapshot = "//:stackage_snapshot.yaml",
     packages = ["zlib"],
-    snapshot = test_stack_snapshot,
     stack_snapshot_json = "//:stackage-zlib-snapshot.json" if not is_windows else None,
 )
 
@@ -289,6 +288,7 @@ load(
     "asterius_dependencies_bindist",
     "asterius_dependencies_nix",
     "rules_haskell_asterius_toolchains",
+    "toolchain_libraries",
 )
 
 (asterius_dependencies_nix(
@@ -584,6 +584,27 @@ load("//tools:repositories.bzl", "rules_haskell_worker_dependencies")
 
 rules_haskell_worker_dependencies()
 
+# Stack snapshot repository for testing non standard toolchains
+# The toolchain_libraries rule provide a default value for the toolchain_libraries
+# variable, so we can load it even if we are not on linux.
+
+toolchain_libraries(
+    name = "toolchains_libraries",
+    repository = "linux_amd64_asterius" if is_linux else "",
+)
+
+load("@toolchains_libraries//:toolchain_libraries.bzl", "toolchain_libraries")
+
+stack_snapshot(
+    name = "stackage_asterius",
+    local_snapshot = "@rules_haskell//tests/asterius/stack_toolchain_libraries:snapshot.yaml",
+    packages = [
+        "xhtml",
+    ],
+    stack_snapshot_json = "@rules_haskell//tests/asterius/stack_toolchain_libraries:snapshot.json",
+    toolchain_libraries = toolchain_libraries,
+) if is_linux else None
+
 local_repository(
     name = "tutorial",
     path = "tutorial",

constants.bzl

@@ -1,3 +1,2 @@
 test_ghc_version = "8.10.7"
-test_stack_snapshot = "lts-18.18"
 test_asterius_version = "0.0.1"

ghcide-stack-snapshot.yaml

@@ -10,3 +10,12 @@ packages:
 - implicit-hie-cradle-0.3.0.2
 - lsp-test-0.11.0.7
 - retrie-0.1.1.1
+
+# We drop the Win32 package from the stack snapshot so that stack considers it a toolchain library.
+# In this case we will use the Win32 provided by the compiler instead of recompiling it.
+# 
+# Recompiling it should be fine for future versions of Win32,
+# but with versions <= 2.13.2.0 we encounter the following issue:
+# https://github.com/haskell/win32/issues/193
+drop-packages:
+- Win32

haskell/asterius/BUILD.bazel

@@ -21,6 +21,13 @@ platform(
     ],
 )
 
+config_setting(
+    name = "asterius",
+    constraint_values = [
+        "@platforms//cpu:wasm32",
+    ],
+)
+
 # Toolchain type for asterius specific tools such as ahc-dist,
 # which are not part of the regular haskell toolchain.
 toolchain_type(

haskell/asterius/repositories.bzl

@@ -171,13 +171,20 @@ def _ahc_impl(ctx):
         "BUILD",
         filepaths["@rules_haskell//haskell:ahc.BUILD.tpl"],
         substitutions = {
-            "%{toolchain_libraries}": toolchain_libraries,
+            "%{toolchain_libraries}": toolchain_libraries["file_content"],
             "%{toolchain}": toolchain,
             "%{asterius_toolchain}": asterius_toolchain,
         },
         executable = False,
     )
 
+    # We make the list of toolchain libraries available for loading in the WORKSPACE file.
+    ctx.file(
+        "toolchain_libraries.bzl",
+        executable = False,
+        content = "toolchain_libraries = {}".format(toolchain_libraries["toolchain_libraries"]),
+    )
+
 _ahc = repository_rule(
     _ahc_impl,
     local = False,
@@ -356,3 +363,33 @@ def asterius_dependencies_custom(**kwargs):
         ```
     """
     _asterius_dependencies_custom(**kwargs)
+
+def _toolchain_libraries_impl(repository_ctx):
+    if repository_ctx.attr.repository:
+        repository_ctx.file(
+            "toolchain_libraries.bzl",
+            executable = False,
+            content = """\
+load("@{}//:toolchain_libraries.bzl", _toolchain_libraries = "toolchain_libraries")
+toolchain_libraries = _toolchain_libraries
+    """.format(repository_ctx.attr.repository),
+        )
+    else:
+        repository_ctx.file(
+            "toolchain_libraries.bzl",
+            executable = False,
+            content = "toolchain_libraries = None",
+        )
+
+    repository_ctx.file("BUILD", executable = False, content = "")
+
+toolchain_libraries = repository_rule(
+    _toolchain_libraries_impl,
+    attrs = {
+        "repository": attr.string(
+            default = "",
+            doc = "An optional repository from which we recover the toolchain_libraries variable. If absent or empty, the toolchain_libraries variable will be equal to None.",
+        ),
+    },
+    doc = "Optionally recovers the `toolchain_libraries` variable from another repository",
+)