feat: support --noCheck for parallel transpiling without type-checking

examples/isolated_typecheck/BUILD.bazel

@@ -0,0 +1,7 @@
+load("@aspect_rules_ts//ts:defs.bzl", "ts_config")
+
+ts_config(
+    name = "tsconfig",
+    src = "tsconfig.json",
+    visibility = [":__subpackages__"],
+)

examples/isolated_typecheck/backend/BUILD.bazel

@@ -0,0 +1,16 @@
+load("@aspect_bazel_lib//lib:testing.bzl", "assert_outputs")
+load("@aspect_rules_ts//ts:defs.bzl", "ts_project")
+
+ts_project(
+    name = "backend",
+    declaration = True,
+    isolated_typecheck = True,
+    tsconfig = "//examples/isolated_typecheck:tsconfig",
+    deps = ["//examples/isolated_typecheck/core"],
+)
+
+assert_outputs(
+    name = "test_backend_default_outputs",
+    actual = "backend",
+    expected = ["examples/isolated_typecheck/backend/index.js"],
+)

examples/isolated_typecheck/backend/index.ts

@@ -0,0 +1,10 @@
+import type { IntersectionType } from '../core'
+
+// Example object of IntersectionType
+const myObject: IntersectionType = {
+    a: 42,
+    b: 'backend',
+    c: true,
+}
+
+console.log(myObject)

examples/isolated_typecheck/core/BUILD.bazel

@@ -0,0 +1,9 @@
+load("@aspect_rules_ts//ts:defs.bzl", "ts_project")
+
+ts_project(
+    name = "core",
+    declaration = True,
+    isolated_typecheck = True,
+    tsconfig = "//examples/isolated_typecheck:tsconfig",
+    visibility = ["//examples/isolated_typecheck:__subpackages__"],
+)

examples/isolated_typecheck/core/index.ts

@@ -0,0 +1,20 @@
+/**
+ * A file with some non-trivial types, so type-checking it may take some time.
+ * This helps to motivate the example: we'd like to be able to type-check the frontend and backend in parallel with this file.
+ */
+type UnionToIntersection<U> = (U extends any ? (k: U) => void : never) extends (
+    k: infer I
+) => void
+    ? I
+    : never
+
+// Example usage
+type UnionType = { a: number } | { b: string } | { c: boolean }
+
+export type IntersectionType = UnionToIntersection<UnionType>
+
+export const MyIntersectingValue: IntersectionType = {
+    a: 1,
+    b: '2',
+    c: true,
+}

examples/isolated_typecheck/frontend/BUILD.bazel

@@ -0,0 +1,13 @@
+load("@aspect_rules_ts//ts:defs.bzl", "ts_project")
+
+ts_project(
+    name = "frontend",
+    isolated_typecheck = True,
+    tsconfig = {
+        "compilerOptions": {
+            "declaration": True,
+            "isolatedDeclarations": True,
+        },
+    },
+    deps = ["//examples/isolated_typecheck/core"],
+)

examples/isolated_typecheck/frontend/index.ts

@@ -0,0 +1,13 @@
+import type { IntersectionType } from '../core'
+import { MyIntersectingValue } from '../core'
+
+// Example object of IntersectionType
+const myObject: IntersectionType = {
+    a: 42,
+    b: 'frontend',
+    c: true,
+}
+
+const otherObject = MyIntersectingValue
+
+console.log(myObject, otherObject, myObject === otherObject)

examples/isolated_typecheck/tsconfig.json

@@ -0,0 +1,8 @@
+{
+    "compilerOptions": {
+        "isolatedDeclarations": true,
+        "declaration": true
+    },
+    // Workaround https://github.com/microsoft/TypeScript/issues/59036
+    "exclude": []
+}

ts/defs.bzl

@@ -40,6 +40,7 @@ def ts_project(
         assets = [],
         extends = None,
         allow_js = False,
+        isolated_typecheck = False,
         declaration = False,
         source_map = False,
         declaration_map = False,
@@ -153,6 +154,10 @@ def ts_project(
             See https://www.typescriptlang.org/docs/handbook/compiler-options.html#compiler-options
             Typically useful arguments for debugging are `--listFiles` and `--listEmittedFiles`.
 
+        isolated_typecheck: Whether to type-check asynchronously as a separate bazel action.
+            Requires https://devblogs.microsoft.com/typescript/announcing-typescript-5-6/#the---nocheck-option6
+            Requires https://www.typescriptlang.org/docs/handbook/release-notes/typescript-5-5.html#isolated-declarations
+
         transpiler: A custom transpiler tool to run that produces the JavaScript outputs instead of `tsc`.
 
             Under `--@aspect_rules_ts//ts:default_to_tsc_transpiler`, the default is to use `tsc` to produce
@@ -416,6 +421,7 @@ def ts_project(
         incremental = incremental,
         preserve_jsx = preserve_jsx,
         composite = composite,
+        isolated_typecheck = isolated_typecheck,
         declaration = declaration,
         declaration_dir = declaration_dir,
         source_map = source_map,

ts/private/ts_lib.bzl

@@ -87,6 +87,20 @@ https://docs.aspect.build/rulesets/aspect_rules_js/docs/js_library#deps for more
         mandatory = True,
         allow_single_file = [".json"],
     ),
+    "isolated_typecheck": attr.bool(
+        doc = """\
+        Whether type-checking should be a separate action.
+
+        This allows the transpilation action to run without waiting for typings from dependencies.
+
+        Requires a minimum version of typescript 5.6 for the [noCheck](https://www.typescriptlang.org/tsconfig#noCheck)
+        flag which is automatically set on the transpilation action when the typecheck action is isolated.
+
+        Requires [isolatedDeclarations](https://www.typescriptlang.org/tsconfig#isolatedDeclarations)
+        to be set so that declarations can be emitted without dependencies. The use of `isolatedDeclarations` may
+        require significant changes to your codebase and should be done as a pre-requisite to enabling `isolated_typecheck`.
+        """,
+    ),
     "validate": attr.bool(
         doc = """whether to add a Validation Action to verify the other attributes match
             settings in the tsconfig.json file""",