feat: default to latest protobuf rather than pinning (#12)

* feat: use protobuf v27

* chore: update docs

* fix: check in requirements.in

* chore: more docs

* Update release_prep.sh

Author: alexeagle

.github/workflows/release_prep.sh

@@ -23,6 +23,16 @@ cat << EOF
 
 \`\`\`starlark
 bazel_dep(name = "toolchains_protoc", version = "${TAG:1}")
+
+# Optional: choose a version of protoc rather than the latest.
+protoc = use_extension("@toolchains_protoc//protoc:extensions.bzl", "protoc")
+protoc.toolchain(
+    # Creates a repository to satisfy well-known-types dependencies such as
+    # deps=["@com_google_protobuf//:any_proto"]
+    google_protobuf = "com_google_protobuf",
+    # Pin to any version of protoc
+    version = "v26.0",
+)
 \`\`\`
 
 ## Using WORKSPACE

MODULE.bazel

@@ -13,7 +13,7 @@ bazel_dep(name = "platforms", version = "0.0.8")
 protoc = use_extension("//protoc:extensions.bzl", "protoc")
 protoc.toolchain(
     google_protobuf = "com_google_protobuf",
-    version = "v25.3",
+    version = "LATEST",
 )
 use_repo(protoc, "com_google_protobuf", "toolchains_protoc_hub")
 
@@ -23,32 +23,24 @@ bazel_dep(name = "aspect_bazel_lib", version = "1.32.1", dev_dependency = True)
 bazel_dep(name = "buildifier_prebuilt", version = "6.1.2", dev_dependency = True)
 bazel_dep(name = "aspect_rules_py", version = "0.7.1", dev_dependency = True)
 bazel_dep(name = "rules_java", version = "7.4.0", dev_dependency = True)
-bazel_dep(name = "rules_python", version = "0.31.0", dev_dependency = True)
-
-# # Update to include
-# https://github.com/bazelbuild/rules_python/pull/1577
-git_override(
-    module_name = "rules_python",
-    commit = "3edcae33dcc43051ca6f200c2d0cb3692df79d03",
-    remote = "https://github.com/bazelbuild/rules_python.git",
-)
+bazel_dep(name = "rules_python", version = "0.32.2", dev_dependency = True)
+bazel_dep(name = "rules_go", version = "0.48.0", dev_dependency = True)
+bazel_dep(name = "rules_uv", version = "0.10.0", dev_dependency = True)
 
 register_toolchains(
     "//examples/lang_toolchains:all",
     dev_dependency = True,
 )
 
 # Shows how a typical Python user fetches all the dependencies of their app, including the protobuf runtime
-pip = use_extension(
+dev_pip = use_extension(
     "@rules_python//python/extensions:pip.bzl",
     "pip",
     dev_dependency = True,
 )
-pip.parse(
+dev_pip.parse(
     hub_name = "pypi",
     python_version = "3.11",
     requirements_lock = "//examples/lang_toolchains:requirements.txt",
 )
-use_repo(pip, "pypi")
-
-bazel_dep(name = "rules_go", version = "0.48.0")
+use_repo(dev_pip, "pypi")

README.md

@@ -18,17 +18,17 @@ Using Protocol Buffers with Bazel has always been difficult.
 ## Support matrix
 
 Minimum versions:
+
 - Bazel: 7.0.0
 - rules_proto: 6.0.0
 
-| Language | Support | Example or Issue |
-|----------|---------|------------------|
-| Java     | Yes     | [example](./examples/java) |
+| Language | Support | Example or Issue             |
+| -------- | ------- | ---------------------------- |
+| Java     | Yes     | [example](./examples/java)   |
 | Python   | Yes     | [example](./examples/python) |
-| Rust     |         | https://github.com/bazelbuild/rules_rust/issues/2627 |
-| Go       |         | https://github.com/bazelbuild/rules_go/issues/3895 |
+| Go       | Yes     | [example](./examples/go)     |
 
-Your language missing? Please file the upstream issue and send a PR to update this table!
+For all other languages, see https://github.com/bazelbuild/rules_proto/discussions/213
 
 ## Installation
 
@@ -56,43 +56,33 @@ using whatever Bazel rule you chose for interacting with package managers
 - JavaScript: https://www.npmjs.com/package/protobufjs
 - Go: https://pkg.go.dev/google.golang.org/protobuf/runtime
 
-Second, declare the toolchain in a `BUILD` file. It looks like the following
-(where `LANG`, `--flag_to_protoc`, and `runtime` are replaced
+For rulesets that need a "lang toolchain", declare one in a `BUILD` file.
+It looks like the following (where `LANG`, `--flag_to_protoc`, and `runtime` are replaced
 with appropriate values for the language and the label of the runtime you installed).
 
-You can choose a Bazel package where this goes; we recommend `/tools/protoc/BUILD.bazel`.
+You can choose a Bazel package where this goes; we recommend `/tools/toolchains/BUILD.bazel`.
 
 ```starlark
 load("@rules_proto//proto:defs.bzl", "proto_lang_toolchain")
+
 proto_lang_toolchain(
     name = "protoc_LANG_toolchain",
     command_line = "--flag_to_protoc=%s",
     progress_message = "Generating LANG proto_library %{label}",
     runtime = "@some-external//lib",
-)
-```
-
-Finally, in the same `BUILD` file, declare the registration target...
-
-```starlark
-toolchain(
-    name = "protoc_LANG_toolchain.registration",
-    toolchain = ":protoc_LANG_toolchain",
-    # This type should be declared by the language rules:
+    # This target should be declared by the language rules:
     toolchain_type = "@rules_LANG//path/to/proto:toolchain_type",
 )
 ```
 
-...and then register it, either in `MODULE.bazel` or `WORKSPACE`:
+Then register the toolchains, either in `MODULE.bazel` or `WORKSPACE`:
 
 ```starlark
-register_toolchains("//tools/protoc:all")
+register_toolchains("//tools/toolchains:all")
 ```
 
 See `examples` for several language rules like `py_proto_library` and `java_proto_library`.
 
-Note that there is NO dependency on `@com_google_protobuf` anywhere.
-
 ### Troubleshooting
 
 What if you still see that protoc is compiling? This means that there is still a transitive dependency on the
@@ -110,7 +100,7 @@ What if you still see that protoc is compiling? This means that there is still a
 1. That distribution includes the "well known types" such as `timestamp.proto`
 1. The protobuf runtimes for each language are distributed to the appropriate package manager such as npm or PyPI.
 1. Bazel 7 introduced `--incompatible_enable_proto_toolchain_resolution` to allow us fetch `protoc` rather than re-build it!
-  That flag ALSO decouples how each built-in language rule (Java, Python, C++, etc.) locates the runtime.
+   That flag ALSO decouples how each built-in language rule (Java, Python, C++, etc.) locates the runtime.
 
 Thanks to that flag, this repo simply contains a toolchain that resolves those pre-built binaries.
 In the user's repository, there's a small BUILD file where the toolchain is configured.

WORKSPACE.bazel

@@ -5,7 +5,7 @@ load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_jar")
 # Note: this is simpler than using rules_jvm_external with a maven installation,
 # but users would probably get this JAR file that way.
 http_jar(
-    name = "protobuf-java_3_25_3",
-    sha256 = "e90d8ddb963b20a972a6a59b5093ade2b07cbe546cab3279aaf4383260385f58",
-    urls = ["https://repo1.maven.org/maven2/com/google/protobuf/protobuf-java/3.25.3/protobuf-java-3.25.3.jar"],
+    name = "protobuf-java",
+    sha256 = "0532ad1024d62361561acaedb974d7d16889e7670b36e23e9321dd6b9d334ef9",
+    urls = ["https://repo1.maven.org/maven2/com/google/protobuf/protobuf-java/4.27.0-RC3/protobuf-java-4.27.0-RC3.jar"],
 )

examples/java/BUILD

@@ -4,6 +4,6 @@ java_binary(
     main_class = "Main",
     deps = [
         "//examples:foo_java_proto",
-        "@protobuf-java_3_25_3//jar",
+        "@protobuf-java//jar",
     ],
 )

examples/lang_toolchains/BUILD

@@ -1,4 +1,11 @@
 load("@rules_proto//proto:defs.bzl", "proto_lang_toolchain")
+load("@rules_uv//uv:pip.bzl", "pip_compile")
+
+pip_compile(
+    name = "generate_requirements_txt",
+    requirements_in = "requirements.in",
+    requirements_txt = "requirements.txt",
+)
 
 # Configure protoc to have the right arguments for generating Python stubs.
 proto_lang_toolchain(
@@ -13,6 +20,6 @@ proto_lang_toolchain(
     name = "protoc_java_toolchain",
     command_line = "--java_out=%s",
     progress_message = "Generating Java proto_library %{label}",
-    runtime = "@protobuf-java_3_25_3//jar",
+    runtime = "@protobuf-java//jar",
     toolchain_type = "@rules_java//java/proto:toolchain_type",
 )

examples/lang_toolchains/requirements.in

@@ -0,0 +1 @@
+protobuf==5.27.0

examples/lang_toolchains/requirements.txt

@@ -1,19 +1,17 @@
-#
-# This file is autogenerated by pip-compile with Python 3.11
-# by the following command:
-#
-#    bazel run //examples/lang_toolchains:requirements.update
-#
-protobuf==5.26.0 \
-    --hash=sha256:2c334550e1cb4efac5c8a3987384bf13a4334abaf5ab59e40479e7b70ecd6b19 \
-    --hash=sha256:6ee9d1aa02f951c5ce10bf8c6cfb7604133773038e33f913183c8b5201350600 \
-    --hash=sha256:7e47c57303466c867374a17b2b5e99c5a7c8b72a94118e2f28efb599f19b4069 \
-    --hash=sha256:82f5870d74c99addfe4152777bdf8168244b9cf0ac65f8eccf045ddfa9d80d9b \
-    --hash=sha256:8eef61a90631c21b06b4f492a27e199a269827f046de3bb68b61aa84fcf50905 \
-    --hash=sha256:a49b6c5359bf34fb7bf965bf21abfab4476e4527d822ab5289ee3bf73f291159 \
-    --hash=sha256:ca825f4eecb8c342d2ec581e6a5ad1ad1a47bededaecd768e0d3451ae4aaac2b \
-    --hash=sha256:dfd29f6eb34107dccf289a93d44fb6b131e68888d090b784b691775ac84e8213 \
-    --hash=sha256:e184175276edc222e2d5e314a72521e10049938a9a4961fe4bea9b25d073c03f \
-    --hash=sha256:efd4f5894c50bd76cbcfdd668cd941021333861ed0f441c78a83d8254a01cc9f \
-    --hash=sha256:f9ecc8eb6f18037e0cbf43256db0325d4723f429bca7ef5cd358b7c29d65f628
+# This file was autogenerated by uv via the following command:
+#    bazel run @@//examples/lang_toolchains:generate_requirements_txt
+--index-url https://pypi.org/simple
+
+protobuf==5.27.0 \
+    --hash=sha256:07f2b9a15255e3cf3f137d884af7972407b556a7a220912b252f26dc3121e6bf \
+    --hash=sha256:2f83bf341d925650d550b8932b71763321d782529ac0eaf278f5242f513cc04e \
+    --hash=sha256:56937f97ae0dcf4e220ff2abb1456c51a334144c9960b23597f044ce99c29c89 \
+    --hash=sha256:587be23f1212da7a14a6c65fd61995f8ef35779d4aea9e36aad81f5f3b80aec5 \
+    --hash=sha256:673ad60f1536b394b4fa0bcd3146a4130fcad85bfe3b60eaa86d6a0ace0fa374 \
+    --hash=sha256:744489f77c29174328d32f8921566fb0f7080a2f064c5137b9d6f4b790f9e0c1 \
+    --hash=sha256:7cb65fc8fba680b27cf7a07678084c6e68ee13cab7cace734954c25a43da6d0f \
+    --hash=sha256:a17f4d664ea868102feaa30a674542255f9f4bf835d943d588440d1f49a3ed15 \
+    --hash=sha256:aabbbcf794fbb4c692ff14ce06780a66d04758435717107c387f12fb477bf0d8 \
+    --hash=sha256:b276e3f477ea1eebff3c2e1515136cfcff5ac14519c45f9b4aa2f6a87ea627c4 \
+    --hash=sha256:f51f33d305e18646f03acfdb343aac15b8115235af98bc9f844bf9446573827b
     # via -r examples/lang_toolchains/requirements.in

protoc/private/prebuilt_protoc_toolchain.bzl

@@ -24,6 +24,8 @@ GOOGLE_PROTOBUF_DEP_EDGES = {
 
 def _prebuilt_protoc_repo_impl(rctx):
     release_version = rctx.attr.version
+    if release_version == "LATEST":
+        release_version = PROTOC_VERSIONS.keys()[0]
 
     filename = "{}-{}-{}.zip".format(
         "protoc",