[bazel] Add a BUILD file for jax/extend, and add more granular target…

…s for individual pieces of extend.

In general we'd like to use more granular BUILD targets rather than larger monolithic targets. If nothing else, they interact better with pytype.

This change is in preparation for adding the JAX MLIR bindings to jax.extend, since they are something that JAX users sometimes need especially for defining custom ops.

PiperOrigin-RevId: 587893573

jax/BUILD

@@ -82,6 +82,7 @@ package_group(
 
 package_group(
     name = "jax_extend_users",
+    includes = [":internal"],
     packages = [
         # Intentionally avoid jax dependencies on jax.extend.
         # See https://jax.readthedocs.io/en/latest/jep/15856-jex.html
@@ -968,11 +969,17 @@ pytype_library(
     ],
 )
 
-pytype_library(
+# TODO(phawkins): remove this target in favor of the finer-grained targets in jax/extend/...
+pytype_strict_library(
     name = "extend",
-    srcs = glob(["extend/**/*.py"]),
     visibility = [":jax_extend_users"],
-    deps = [":jax"],
+    deps = [
+        "//jax/extend",
+        "//jax/extend:core",
+        "//jax/extend:linear_util",
+        "//jax/extend:random",
+        "//jax/extend:source_info_util",
+    ],
 )
 
 pytype_library(

jax/extend/BUILD

@@ -0,0 +1,58 @@
+# Copyright 2023 The JAX Authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+load(
+    "//jaxlib:jax.bzl",
+    "pytype_strict_library",
+)
+
+package(
+    default_applicable_licenses = [],
+    default_visibility = ["//jax:jax_extend_users"],
+)
+
+pytype_strict_library(
+    name = "extend",
+    srcs = ["__init__.py"],
+    deps = [
+        ":core",
+        ":linear_util",
+        ":random",
+        ":source_info_util",
+    ],
+)
+
+pytype_strict_library(
+    name = "core",
+    srcs = ["core.py"],
+    deps = ["//jax:abstract_arrays"],
+)
+
+pytype_strict_library(
+    name = "linear_util",
+    srcs = ["linear_util.py"],
+    deps = ["//jax:core"],
+)
+
+pytype_strict_library(
+    name = "random",
+    srcs = ["random.py"],
+    deps = ["//jax"],
+)
+
+pytype_strict_library(
+    name = "source_info_util",
+    srcs = ["source_info_util.py"],
+    deps = ["//jax:source_info_util"],
+)