feat: make it easier to resolve jq/yq toolchains from a repository rule

e2e/run_jq_symlinked_bin.sh

@@ -0,0 +1,14 @@
+#!/bin/bash
+
+set -e
+
+case "$(uname -s)" in
+    CYGWIN*|MINGW32*|MSYS*|MINGW*)
+        bazel run @jq//:jq.exe -- --null-input .a=5
+        ;;
+
+    *)
+        bazel run @jq//:jq -- --null-input .a=5
+        ;;
+esac
+

e2e/run_yq_symlinked_bin.sh

@@ -0,0 +1,13 @@
+#!/bin/bash
+
+set -e
+
+case "$(uname -s)" in
+    CYGWIN*|MINGW32*|MSYS*|MINGW*)
+        bazel run @yq//:yq.exe -- --null-input .a=5
+        ;;
+
+    *)
+        bazel run @yq//:yq -- --null-input .a=5
+        ;;
+esac

lib/private/jq_toolchain.bzl

@@ -190,35 +190,25 @@ jq_platform_repo = repository_rule(
 )
 
 def _jq_host_alias_repo(repository_ctx):
+    ext = ".exe" if repo_utils.is_windows(repository_ctx) else ""
+
     # Base BUILD file for this repository
     repository_ctx.file("BUILD.bazel", """# Generated by @aspect_bazel_lib//lib/private:jq_toolchain.bzl
 package(default_visibility = ["//visibility:public"])
-alias(name = "jq", actual = "@{name}_{platform}//:jq")
-exports_files(["index.bzl"])
+exports_files(["jq{ext}"])
 """.format(
-        name = repository_ctx.name,
+        ext = ext,
+    ))
+
+    repository_ctx.symlink("../{name}_{platform}/jq{ext}".format(
+        name = repository_ctx.attr.name,
         platform = repo_utils.platform(repository_ctx),
-    ))
-
-    # index.bzl file for this repository
-    repository_ctx.file("index.bzl", content = """# Generated by @aspect_bazel_lib//lib/private:jq_toolchain.bzl
-host_platform="{host_platform}"
-
-def bin():
-    "Returns the label of the jq binary for the host platform"
-    return Label("@{name}_{host_platform}//:jq{maybe_windows}")
-""".format(
-        name = repository_ctx.name,
-        host_platform = repo_utils.platform(repository_ctx),
-        maybe_windows = ".exe" if repo_utils.is_windows(repository_ctx) else "",
-    ))
+        ext = ext,
+    ), "jq{ext}".format(ext = ext))
 
 jq_host_alias_repo = repository_rule(
     _jq_host_alias_repo,
     doc = """Creates a repository with a shorter name meant for the host platform, which contains
-
-    - A BUILD.bazel file declaring aliases to the host platform's binaries
-    - index.bzl containing a `host_platform` constant and a `bin()` function that returns the label
-      to the jq binary for the host platform
+    a BUILD.bazel file that exports symlinks to the host platform's binaries
     """,
 )

lib/private/repo_utils.bzl

@@ -77,8 +77,8 @@ def _platform(rctx):
     # Once we drop support for anything older than Bazel 5.1.1 than we can simplify
     # this function.
     if os == "windows":
-        proc_arch = (_get_env_var(rctx, "PROCESSOR_ARCHITECTURE", "", False) or
-                     _get_env_var(rctx, "PROCESSOR_ARCHITEW6432", "", False))
+        proc_arch = (_get_env_var(rctx, "PROCESSOR_ARCHITECTURE", "") or
+                     _get_env_var(rctx, "PROCESSOR_ARCHITEW6432", ""))
         if proc_arch == "ARM64":
             arch = "arm64"
         else:

lib/private/yq_toolchain.bzl

@@ -224,35 +224,25 @@ yq_platform_repo = repository_rule(
 )
 
 def _yq_host_alias_repo(repository_ctx):
+    ext = ".exe" if repo_utils.is_windows(repository_ctx) else ""
+
     # Base BUILD file for this repository
     repository_ctx.file("BUILD.bazel", """# Generated by @aspect_bazel_lib//lib/private:yq_toolchain.bzl
 package(default_visibility = ["//visibility:public"])
-alias(name = "yq", actual = "@{name}_{platform}//:yq")
-exports_files(["index.bzl"])
+exports_files(["yq{ext}"])
 """.format(
-        name = repository_ctx.name,
+        ext = ext,
+    ))
+
+    repository_ctx.symlink("../{name}_{platform}/yq{ext}".format(
+        name = repository_ctx.attr.name,
         platform = repo_utils.platform(repository_ctx),
-    ))
-
-    # index.bzl file for this repository
-    repository_ctx.file("index.bzl", content = """# Generated by @aspect_bazel_lib//lib/private:yq_toolchain.bzl
-host_platform="{host_platform}"
-
-def bin():
-    "Returns the label of the yq binary for the host platform"
-    return Label("@{name}_{host_platform}//:yq{maybe_windows}")
-""".format(
-        name = repository_ctx.name,
-        host_platform = repo_utils.platform(repository_ctx),
-        maybe_windows = ".exe" if repo_utils.is_windows(repository_ctx) else "",
-    ))
+        ext = ext,
+    ), "yq{ext}".format(ext = ext))
 
 yq_host_alias_repo = repository_rule(
     _yq_host_alias_repo,
     doc = """Creates a repository with a shorter name meant for the host platform, which contains
-
-    - A BUILD.bazel file declaring aliases to the host platform's binaries
-    - index.bzl containing a `host_platform` constant and a `bin()` function that returns the label
-      to the yq binary for the host platform
+    a BUILD.bazel file that exports symlinks to the host platform's binaries
     """,
 )