Add support for py_binary tools (#10)

Also adds tests for Python toolchains and their `python3` binary.

bazel_env.bzl

@@ -176,7 +176,7 @@ _tool = rule(
     implementation = _tool_impl,
     attrs = {
         "target": attr.label(
-            allow_single_file = True,
+            allow_files = True,
             cfg = _flip_output_dir,
             executable = True,
         ),

examples/BUILD.bazel

@@ -1,12 +1,14 @@
 load("@buildozer//:buildozer.bzl", "BUILDOZER_LABEL")
 load("@bazel_env.bzl", "bazel_env")
+load("@rules_python//python:py_binary.bzl", "py_binary")
 
 # `bazel run //:bazel_env` prints a summary and setup steps.
 bazel_env(
     name = "bazel_env",
     toolchains = {
         "cc_toolchain": "@bazel_tools//tools/cpp:current_cc_toolchain",
         "jdk": "@rules_java//toolchains:current_host_java_runtime",
+        "python": "@rules_python//python:current_py_toolchain",
     },
     tools = {
         # Tool paths can reference the Make variables provided by toolchains.
@@ -18,6 +20,8 @@ bazel_env(
         "jar": "$(JAVABASE)/bin/jar",
         "java": "$(JAVA)",
         "jq": ":jq",
+        "python": "$(PYTHON3)",
+        "python_tool": ":python_tool",
     },
 )
 
@@ -30,6 +34,17 @@ alias(
     }),
 )
 
+py_binary(
+    name = "python_tool",
+    srcs = ["python_tool.py"],
+    deps = [":python_tool_lib"],
+)
+
+py_library(
+    name = "python_tool_lib",
+    srcs = ["python_tool_lib.py"],
+)
+
 # Lines below are not part of the example, they are used to test the example.
 
 sh_test(

examples/MODULE.bazel

@@ -13,13 +13,20 @@ bazel_dep(name = "buildifier_prebuilt", version = "6.4.0")
 bazel_dep(name = "buildozer", version = "7.1.2")
 bazel_dep(name = "rules_go", version = "0.47.1")
 bazel_dep(name = "rules_java", version = "7.5.0")
+bazel_dep(name = "rules_python", version = "0.32.2")
 bazel_dep(name = "platforms", version = "0.0.10")
 
 # Don't update the versions below, they are only used to verify the hermeticity of bazel_env.
 
 go_sdk = use_extension("@rules_go//go:extensions.bzl", "go_sdk")
 go_sdk.download(version = "1.20.14")
 
+python = use_extension("@rules_python//python/extensions:python.bzl", "python")
+python.toolchain(
+    is_default = True,
+    python_version = "3.11.8",
+)
+
 http_file = use_repo_rule("@bazel_tools//tools/build_defs/repo:http.bzl", "http_file")
 
 http_file(

examples/bazel_env_test.sh

@@ -9,9 +9,10 @@ build_workspace_directory="$(dirname "$(readlink -f MODULE.bazel)")"
 function assert_cmd_output() {
   local -r cmd="$1"
   local -r expected_output="$2"
+  local -r extra_path="${3:-}"
 
   local -r bazel_env="$build_workspace_directory/bazel-out/bazel_env-opt/bin/bazel_env/bin"
-  local -r actual_output="$(PATH="$bazel_env:/bin" $cmd 2>&1 | head -n 1 || true)"
+  local -r actual_output="$(PATH="$bazel_env:/bin$extra_path" $cmd 2>&1 | head -n 1 || true)"
 
   # Allow for wildcard matching first.
   if [[ $actual_output == $expected_output ]]; then
@@ -55,17 +56,20 @@ expected_output='
 ✅ direnv added bazel-out/bazel_env-opt/bin/bazel_env/bin to PATH
 
 Tools available in PATH:
-  * bazel-cc:   $(CC)
-  * buildifier: @buildifier_prebuilt//:buildifier
-  * buildozer:  @@buildozer~~buildozer_binary~buildozer_binary//:buildozer.exe
-  * go:         @rules_go//go
-  * jar:        $(JAVABASE)/bin/jar
-  * java:       $(JAVA)
-  * jq:         :jq
+  * bazel-cc:    $(CC)
+  * buildifier:  @buildifier_prebuilt//:buildifier
+  * buildozer:   @@buildozer~~buildozer_binary~buildozer_binary//:buildozer.exe
+  * go:          @rules_go//go
+  * jar:         $(JAVABASE)/bin/jar
+  * java:        $(JAVA)
+  * jq:          :jq
+  * python:      $(PYTHON3)
+  * python_tool: :python_tool
 
 Toolchains available at stable relative paths:
   * cc_toolchain: bazel-out/bazel_env-opt/bin/bazel_env/toolchains/cc_toolchain
-  * jdk:          bazel-out/bazel_env-opt/bin/bazel_env/toolchains/jdk'
+  * jdk:          bazel-out/bazel_env-opt/bin/bazel_env/toolchains/jdk
+  * python:       bazel-out/bazel_env-opt/bin/bazel_env/toolchains/python'
 
 diff <(echo "$expected_output") <(echo "$status_out") || exit 1
 
@@ -82,8 +86,12 @@ assert_cmd_output "go version" "go version go1.20.14 $(uname|tr '[:upper:]' '[:l
 assert_cmd_output "jar --version" "jar 17.0.8.1"
 assert_cmd_output "java --version" "openjdk 17.0.8.1 2023-08-24 LTS"
 assert_cmd_output "jq --version" "jq-1.5"
+assert_cmd_output "python --version" "Python 3.11.8"
+# Bazel's Python launcher requires a system installation of python3.
+assert_cmd_output "python_tool" "python_tool version 0.0.1" ":$(dirname "$(which python3)")"
 
 #### Toolchains ####
 
 [[ -d "$build_workspace_directory/bazel-out/bazel_env-opt/bin/bazel_env/toolchains/cc_toolchain" ]]
 assert_cmd_output "$build_workspace_directory/bazel-out/bazel_env-opt/bin/bazel_env/toolchains/jdk/bin/java --version" "openjdk 17.0.8.1 2023-08-24 LTS"
+assert_cmd_output "$build_workspace_directory/bazel-out/bazel_env-opt/bin/bazel_env/toolchains/python/bin/python3 --version" "Python 3.11.8"

examples/python_tool.py

@@ -0,0 +1,4 @@
+from python_tool_lib import print_version
+
+if __name__ == "__main__":
+    print_version()

examples/python_tool_lib.py

@@ -0,0 +1,2 @@
+def print_version():
+    print("python_tool version 0.0.1")