feat: add is_bazel_6_or_greater utility function (#264)

docs/utils.md

@@ -82,6 +82,47 @@ glob_directories(<a href="#glob_directories-include">include</a>, <a href="#glob
 | <a id="glob_directories-kwargs"></a>kwargs |  <p align="center"> - </p>   |  none |
 
 
+<a id="is_bazel_6_or_greater"></a>
+
+## is_bazel_6_or_greater
+
+<pre>
+is_bazel_6_or_greater()
+</pre>
+
+Detects if the Bazel version being used is greater than or equal to 6 (including Bazel 6 pre-releases and RCs).
+
+Detecting Bazel 6 or greater is particularly useful in rules as slightly different code paths may be needed to
+support bzlmod which was added in Bazel 6.
+
+Unlike the undocumented `native.bazel_version`, which only works in WORKSPACE and repository rules, this function can
+be used in rules and BUILD files.
+
+An alternate approach to make the Bazel version available in BUILD files and rules would be to
+use the [host_repo](https://github.com/aspect-build/bazel-lib/blob/main/docs/host_repo.md) repository rule
+which contains the bazel_version in the exported `host` struct:
+
+WORKSPACE:
+```
+load("@aspect_bazel_lib//lib:host_repo.bzl", "host_repo")
+host_repo(name = "aspect_bazel_lib_host")
+```
+
+BUILD.bazel:
+```
+load("@aspect_bazel_lib_host//:defs.bzl", "host")
+print(host.bazel_version)
+```
+
+That approach, however, incurs a cost in the user's WORKSPACE.
+
+
+
+**RETURNS**
+
+True if the Bazel version being used is greater than or equal to 6 (including pre-releases and RCs)
+
+
 <a id="is_external_label"></a>
 
 ## is_external_label

lib/private/utils.bzl

@@ -150,12 +150,48 @@ def _default_timeout(size, timeout):
 
     return timeout
 
+def _is_bazel_6_or_greater():
+    """Detects if the Bazel version being used is greater than or equal to 6 (including Bazel 6 pre-releases and RCs).
+
+    Detecting Bazel 6 or greater is particularly useful in rules as slightly different code paths may be needed to
+    support bzlmod which was added in Bazel 6.
+
+    Unlike the undocumented `native.bazel_version`, which only works in WORKSPACE and repository rules, this function can
+    be used in rules and BUILD files.
+
+    An alternate approach to make the Bazel version available in BUILD files and rules would be to
+    use the [host_repo](https://github.com/aspect-build/bazel-lib/blob/main/docs/host_repo.md) repository rule
+    which contains the bazel_version in the exported `host` struct:
+
+    WORKSPACE:
+    ```
+    load("@aspect_bazel_lib//lib:host_repo.bzl", "host_repo")
+    host_repo(name = "aspect_bazel_lib_host")
+    ```
+
+    BUILD.bazel:
+    ```
+    load("@aspect_bazel_lib_host//:defs.bzl", "host")
+    print(host.bazel_version)
+    ```
+
+    That approach, however, incurs a cost in the user's WORKSPACE.
+
+    Returns:
+        True if the Bazel version being used is greater than or equal to 6 (including pre-releases and RCs)
+    """
+
+    # Hacky way to check if the we're using at least Bazel 6. Would be nice if there was a ctx.bazel_version instead.
+    # native.bazel_version only works in repository rules.
+    return "apple_binary" not in dir(native)
+
 utils = struct(
-    is_external_label = _is_external_label,
+    default_timeout = _default_timeout,
     file_exists = _file_exists,
     glob_directories = _glob_directories,
+    is_bazel_6_or_greater = _is_bazel_6_or_greater,
+    is_external_label = _is_external_label,
     path_to_workspace_root = _path_to_workspace_root,
     propagate_well_known_tags = _propagate_well_known_tags,
     to_label = _to_label,
-    default_timeout = _default_timeout,
 )

lib/utils.bzl

@@ -2,10 +2,11 @@
 
 load("//lib/private:utils.bzl", "utils")
 
-is_external_label = utils.is_external_label
+default_timeout = utils.default_timeout
+file_exists = utils.file_exists
 glob_directories = utils.glob_directories
+is_bazel_6_or_greater = utils.is_bazel_6_or_greater
+is_external_label = utils.is_external_label
 path_to_workspace_root = utils.path_to_workspace_root
 propagate_well_known_tags = utils.propagate_well_known_tags
 to_label = utils.to_label
-file_exists = utils.file_exists
-default_timeout = utils.default_timeout