feat: on upgrade to 2.0, ask user to select transpiler

This avoids everyone getting the slow 'tsc' option just because they didn't consider their options.

.bazelrc.common

@@ -71,6 +71,7 @@ build:freebsd --nolegacy_external_runfiles
 build:openbsd --nolegacy_external_runfiles
 
 build --@aspect_rules_ts//ts:skipLibCheck=honor_tsconfig
+build --@aspect_rules_ts//ts:default_to_tsc_transpiler
 
 # Turn on --incompatible_strict_action_env which was on by default
 # in Bazel 0.21.0 but turned off again in 0.22.0. Follow

WORKSPACE

@@ -30,6 +30,13 @@ nodejs_register_toolchains(
     node_version = "18.12.0",
 )
 
+load("@aspect_rules_swc//swc:repositories.bzl", "LATEST_SWC_VERSION", "swc_register_toolchains")
+
+swc_register_toolchains(
+    name = "swc",
+    swc_version = LATEST_SWC_VERSION,
+)
+
 # For running our own unit tests
 load("@bazel_skylib//:workspace.bzl", "bazel_skylib_workspace")
 

e2e/test/common.bats

@@ -45,6 +45,7 @@ try-import $BATS_TEST_DIRNAME/.bazelrc
 startup --max_idle_secs=10
 build --worker_verbose
 build --@aspect_rules_ts//ts:skipLibCheck=honor_tsconfig
+build --@aspect_rules_ts//ts:default_to_tsc_transpiler
 EOF
 
 

internal_deps.bzl

@@ -48,3 +48,10 @@ def rules_ts_internal_deps():
             "https://github.com/keith/buildifier-prebuilt/archive/6.1.0.tar.gz",
         ],
     )
+
+    http_archive(
+        name = "aspect_rules_swc",
+        sha256 = "b647c7c31feeb7f9330fff08b45f8afe7de674d3a9c89c712b8f9d1723d0c8f9",
+        strip_prefix = "rules_swc-1.0.1",
+        url = "https://github.com/aspect-build/rules_swc/releases/download/v1.0.1/rules_swc-v1.0.1.tar.gz",
+    )

ts/BUILD.bazel

@@ -51,6 +51,12 @@ string_flag(
     ],
 )
 
+bool_flag(
+    name = "default_to_tsc_transpiler",
+    build_setting_default = False,
+    visibility = ["//visibility:public"],
+)
+
 bool_flag(
     name = "verbose",
     build_setting_default = False,
@@ -94,8 +100,19 @@ config_setting(
     },
 )
 
+config_setting(
+    name = "default_to_tsc_transpiler_flag",
+    flag_values = {
+        ":default_to_tsc_transpiler": "true",
+    },
+)
+
 options(
     name = "options",
+    default_to_tsc_transpiler = select({
+        ":default_to_tsc_transpiler_flag": True,
+        "//conditions:default": False,
+    }),
     skip_lib_check = select(
         {
             "@aspect_rules_ts//ts:skip_lib_check.always": True,

ts/private/options.bzl

@@ -1,8 +1,57 @@
 """A terminal rule collecting verbosity and worker support information"""
 
+transpiler_selection_required = """\
+
+######## Required Transpiler Selection ########
+
+You must select a transpiler for ts_project rules, which produces the .js outputs.
+For more information, see https://docs.aspect.build/rules/aspect_rules_ts/docs/transpiler
+
+1. Use [SWC](https://swc.rs/) for transpiles (recommended)
+
+    This option results in the fastest development round-trip time, however it may have subtle
+    compatibility issues: https://github.com/aspect-build/rules_ts/discussions/398
+
+    Add rules_swc to your Bazel project, following instructions on a recent release:
+    https://github.com/aspect-build/rules_swc/releases
+
+    If you don't need any .swcrc, you can run these commands to fixup your `ts_project` calls:
+
+        npx @bazel/buildozer 'fix movePackageToTop' //...:__pkg__
+        npx @bazel/buildozer 'new_load @aspect_rules_swc//swc:defs.bzl swc' //...:__pkg__
+        npx @bazel/buildozer 'set transpiler swc' //...:%ts_project
+        npx @bazel/buildozer 'fix unusedLoads' //...:__pkg__
+    
+    To use an .swcrc file, see option 3 below.
+
+2. Use [tsc](https://www.typescriptlang.org/docs/handbook/compiler-options.html):
+
+    In rules_ts 1.x, the default value is to have TypeScript do both type-checking and transpilation.
+    However, this is the slowest choice, and we no longer recommend this.
+
+    Note that rules_ts used to recommend a "Persistent Worker" mode to keep the `tsc` process running
+    as a background daemon, however this introduces correctness issues in the build and is no longer
+    recommended.
+
+    Add this to /.bazelrc:
+
+        # Use "tsc" as the transpiler when ts_project has no `transpiler` set.
+        build --@aspect_rules_ts//ts:default_to_tsc_transpiler
+
+3. Use a custom transpiler
+
+    You can set the `transpiler` attribute of each `ts_project` to any rule or macro.
+    This could be swc with some custom arguments, babel, esbuild, or any other tool.
+
+    You may want to create a `ts_project` macro within your repository where your choice is setup,
+    then load() from your own macro rather than from @aspect_rules_ts.
+
+##########################################################
+"""
+
 OptionsInfo = provider(
     doc = "Internal: Provider that carries verbosity and global worker support information.",
-    fields = ["args", "verbose", "supports_workers"],
+    fields = ["args", "default_to_tsc_transpiler", "verbose", "supports_workers"],
 )
 
 def _options_impl(ctx):
@@ -40,11 +89,13 @@ def _options_impl(ctx):
         verbose = verbose,
         args = args,
         supports_workers = ctx.attr.supports_workers,
+        default_to_tsc_transpiler = ctx.attr.default_to_tsc_transpiler,
     )
 
 options = rule(
     implementation = _options_impl,
     attrs = {
+        "default_to_tsc_transpiler": attr.bool(),
         "verbose": attr.bool(),
         "supports_workers": attr.bool(),
         "skip_lib_check": attr.bool(),

ts/private/ts_project.bzl

@@ -10,7 +10,7 @@ load("@aspect_rules_js//npm:providers.bzl", "NpmPackageStoreInfo")
 load(":ts_lib.bzl", "COMPILER_OPTION_ATTRS", "OUTPUT_ATTRS", "STD_ATTRS", _lib = "lib")
 load(":ts_config.bzl", "TsConfigInfo")
 load(":ts_validate_options.bzl", _validate_lib = "lib")
-load(":options.bzl", "OptionsInfo")
+load(":options.bzl", "OptionsInfo", "transpiler_selection_required")
 
 # Forked from js_lib_helpers.js_lib_helpers.gather_files_from_js_providers to not
 # include any sources; only transitive declarations & npm linked packages
@@ -207,6 +207,9 @@ This is an error because Bazel does not run actions unless their outputs are nee
     # library, and determines what files are used by a simple non-provider-aware downstream
     # library. Only the JavaScript outputs are intended for use in non-TS-aware dependents.
     if ctx.attr.transpile:
+        if not options.default_to_tsc_transpiler:
+            fail(transpiler_selection_required)
+
         # Special case case where there are no source outputs and we don't have a custom
         # transpiler so we add output_declarations to the default outputs
         default_outputs = output_sources[:] if len(output_sources) else output_declarations[:]