feat(third_party/bazel): Check in rules_haskell from Tweag

third_party/bazel/rules_haskell/haskell/private/haddock_wrapper.sh.tpl

@@ -0,0 +1,49 @@
+#!/usr/bin/env bash
+#
+# Usage: haddock-wrapper.sh <PREBUILD_DEPS_FILE> <HADDOCK_ARGS>
+
+set -eo pipefail
+
+%{env}
+
+PREBUILT_DEPS_FILE=$1
+shift
+
+extra_args=()
+
+for pkg in $(< $PREBUILT_DEPS_FILE)
+do
+    # Assumption: the `haddock-interfaces` field always only contains
+    # exactly one file name. This seems to hold in practice, though the
+    # ghc documentation defines it as:
+    # > (string list) A list of filenames containing Haddock interface files
+    # > (.haddock files) for this package.
+    # If there were more than one file, going by the output for the `depends`,
+    # the file names would be separated by a space character.
+    # https://downloads.haskell.org/~ghc/latest/docs/html/users_guide/packages.html#installedpackageinfo-a-package-specification
+    haddock_interfaces=$(%{ghc-pkg} --simple-output field $pkg haddock-interfaces)
+    haddock_html=$(%{ghc-pkg} --simple-output field $pkg haddock-html)
+
+    # Sometimes the referenced `.haddock` file does not exist
+    # (e.g. for `nixpkgs.haskellPackages` deps with haddock disabled).
+    # In that case, skip this package with a warning.
+    if [[ -f "$haddock_interfaces" ]]
+    then
+        # TODO: link source code,
+        # `--read-interface=$haddock_html,$pkg_src,$haddock_interfaces
+        # https://haskell-haddock.readthedocs.io/en/latest/invoking.html#cmdoption-read-interface
+        extra_args+=("--read-interface=$haddock_html,$haddock_interfaces")
+    else
+        echo "Warning: haddock missing for package $pkg" 1>&2
+    fi
+done
+
+# BSD and GNU mktemp are very different; attempt GNU first
+TEMP=$(mktemp -d 2>/dev/null || mktemp -d -t 'haddock_wrapper')
+trap cleanup 1 2 3 6
+cleanup() { rmdir "$TEMP"; }
+# XXX Override TMPDIR to prevent race conditions on certain platforms.
+# This is a workaround for
+# https://github.com/haskell/haddock/issues/894.
+TMPDIR=$TEMP %{haddock} "${extra_args[@]}" "$@"
+cleanup