feat: support custom dts transpiler (#697)

docs/transpiler.md

@@ -111,16 +111,17 @@ then `load()` from your own macro rather than from `@aspect_rules_ts`.
 
 ## Macro expansion
 
-When `transpiler` is used, then the `ts_project` macro expands to these targets:
+When `no_emit`, `transpiler` or `declaration_transpiler` is set, then the `ts_project` macro expands to these targets:
 
 - `[name]` - the default target which can be included in the `deps` of downstream rules.
     Note that it will successfully build *even if there are typecheck failures* because invoking `tsc` is not needed to produce the default outputs.
     This is considered a feature, as it allows you to have a faster development mode where type-checking is not on the critical path.
-- `[name]_typecheck` - provides typings (`.d.ts` files) as the default output.
+- `[name]_types` - provides typings (`.d.ts` files) as the default outputs.
+    This target is not created if `no_emit` is set.
+- `[name]_typecheck` - provides default outputs asserting type-checking has been run.
     Building this target always causes the typechecker to run.
 - `[name]_typecheck_test` - a [`build_test`] target which simply depends on the `[name]_typecheck` target.
     This ensures that typechecking will be run under `bazel test` with [`--build_tests_only`].
-- `[name]_typings` - internal target which runs the binary from the `tsc` attribute
 -  Any additional target(s) the custom transpiler rule/macro produces.
     (For example, some rules produce one target per TypeScript input file.)
 

examples/transpiler/BUILD.bazel

@@ -1,9 +1,11 @@
 load("@aspect_rules_ts//ts:defs.bzl", "ts_project")
+load("@bazel_skylib//lib:partial.bzl", "partial")
 load("@bazel_skylib//rules:build_test.bzl", "build_test")
 
 # Note, Bazel 6 starlark has lambda so maybe we can stop using partial
 load("@bazel_skylib//rules:write_file.bzl", "write_file")
 load(":babel.bzl", "babel")
+load(":tsc.bzl", "tsc_dts", "tsc_js")
 
 ###
 # See a more full-featured example showing swc and babel at
@@ -90,3 +92,156 @@ build_test(
         "a.js",  # NOTE: does not implement out_dir in this test
     ],
 )
+
+# custom js & dts transpilers, tsc still run for typechecking
+ts_project(
+    name = "custom_transpilers",
+    srcs = ["a.ts"],
+    declaration = True,
+    declaration_transpiler = partial.make(
+        tsc_dts,
+        out_dir = "build-custom_transpilers",
+    ),
+    out_dir = "build-custom_transpilers",
+    source_map = True,
+    transpiler = partial.make(
+        tsc_js,
+        out_dir = "build-custom_transpilers",
+    ),
+)
+
+build_test(
+    name = "custom_transpilers_test",
+    targets = [
+        ":custom_transpilers",
+        ":custom_transpilers_types",
+        ":custom_transpilers_typecheck",
+        "build-custom_transpilers/a.js",
+        "build-custom_transpilers/a.d.ts",
+    ],
+)
+
+# custom js & dts transpilers, noEmit prevents any outputs, typechecking still exists
+ts_project(
+    name = "custom_transpilers-no_emit",
+    srcs = ["a.ts"],
+    declaration_transpiler = tsc_dts,
+    transpiler = tsc_js,
+    tsconfig = {
+        "compilerOptions": {
+            "noEmit": True,
+            "declaration": True,
+            "emitDeclarationOnly": True,
+        },
+    },
+)
+
+build_test(
+    name = "custom_transpilers-no_emit-test",
+    targets = [
+        ":custom_transpilers-no_emit",
+        ":custom_transpilers-no_emit_typecheck",
+    ],
+)
+
+# custom dts transpiler, noEmit prevents any outputs, typechecking still exists
+ts_project(
+    name = "custom_dts_transpiler-no_emit",
+    srcs = ["a.ts"],
+    declaration_transpiler = tsc_dts,
+    tsconfig = {
+        "compilerOptions": {
+            "noEmit": True,
+            "declaration": True,
+            "emitDeclarationOnly": True,
+        },
+    },
+)
+
+build_test(
+    name = "custom_dts_transpiler-no_emit-test",
+    targets = [
+        ":custom_dts_transpiler-no_emit",
+        ":custom_dts_transpiler-no_emit_typecheck",
+    ],
+)
+
+# custom dts transpiler but still invokes tsc for type-checking
+ts_project(
+    name = "custom_dts_transpiler",
+    srcs = ["a.ts"],
+    declaration = True,
+    declaration_transpiler = partial.make(
+        tsc_dts,
+        out_dir = "build-custom_dts_transpiler",
+    ),
+    out_dir = "build-custom_dts_transpiler",
+    source_map = True,
+    transpiler = "tsc",
+)
+
+build_test(
+    name = "custom_dts_transpiler-test",
+    targets = [
+        ":custom_dts_transpiler",
+        ":custom_dts_transpiler_types",
+        ":custom_dts_transpiler_typecheck",
+        "build-custom_dts_transpiler/a.js",
+        "build-custom_dts_transpiler/a.d.ts",
+    ],
+)
+
+# a custom dts transpiler but not actually outputting types
+# should stylle have a _typecheck target
+ts_project(
+    name = "custom_dts_transpiler-no_declarations",
+    srcs = ["a.ts"],
+    declaration_transpiler = partial.make(
+        tsc_dts,
+        out_dir = "build-custom_dts_transpiler-no_declarations",
+    ),
+    out_dir = "build-custom_dts_transpiler-no_declarations",
+    source_map = True,
+    transpiler = "tsc",
+    tsconfig = {
+        "compilerOptions": {
+            "declaration": False,
+        },
+    },
+)
+
+build_test(
+    name = "custom_dts_transpiler-no_declarations-test",
+    targets = [
+        ":custom_dts_transpiler-no_declarations",
+        ":custom_dts_transpiler-no_declarations_typecheck",
+        "build-custom_dts_transpiler-no_declarations/a.js",
+    ],
+)
+
+# custom dts transpiler and only outputting declarations
+ts_project(
+    name = "custom_dts_transpiler-declarations_only",
+    srcs = ["a.ts"],
+    declaration_transpiler = partial.make(
+        tsc_dts,
+        out_dir = "build-custom_dts_transpiler-no_declarations",
+    ),
+    out_dir = "build-custom_dts_transpiler-no_declarations",
+    transpiler = "tsc",
+    tsconfig = {
+        "compilerOptions": {
+            "declaration": True,
+            "emitDeclarationOnly": True,
+        },
+    },
+)
+
+build_test(
+    name = "custom_dts_transpiler-declarations_only-test",
+    targets = [
+        ":custom_dts_transpiler-declarations_only",
+        ":custom_dts_transpiler-declarations_only_typecheck",
+        "build-custom_dts_transpiler-no_declarations/a.d.ts",
+    ],
+)

examples/transpiler/tsc.bzl

@@ -0,0 +1,32 @@
+"Adapter from the TypeScript CLI to the ts_project#transpiler/declaration_transpiler interface"
+
+load("@npm//examples:typescript/package_json.bzl", typescript_bin = "bin")
+
+# tsc configured with --outDir and --emitDeclarationOnly
+def tsc_dts(name, srcs, out_dir, **kwargs):
+    typescript_bin.tsc(
+        name = name,
+        srcs = srcs + ["tsconfig.json"],
+        outs = ["%s/%s" % (out_dir, src.replace(".ts", ".d.ts")) for src in srcs],
+        args = [
+            "-p %s/tsconfig.json" % native.package_name(),
+            "--emitDeclarationOnly",
+            "--outDir %s/%s" % (native.package_name(), out_dir),
+        ],
+        **kwargs
+    )
+
+# tsc configured with --outDir and --declaration false
+def tsc_js(name, srcs, out_dir, **kwargs):
+    typescript_bin.tsc(
+        name = name,
+        srcs = srcs + ["tsconfig.json"],
+        outs = ["%s/%s" % (out_dir, src.replace(".ts", ".js")) for src in srcs],
+        args = [
+            "-p %s/tsconfig.json" % native.package_name(),
+            "--declaration",
+            "false",
+            "--outDir %s/%s" % (native.package_name(), out_dir),
+        ],
+        **kwargs
+    )