feat: support --noEmit for type-checking as a validation action

e2e/test/common.bats

@@ -82,6 +82,7 @@ function tsconfig() {
 	local target="ES2020"
 	local module_resolution="node"
 	local composite="false"
+	local no_emit="false"
 	local trace_resolution="false"
 	local extended_diagnostics="false"
 	while (($# > 0)); do
@@ -111,6 +112,10 @@ function tsconfig() {
 			composite="true"
 			shift
 			;;
+		--no-emit)
+			shift
+			no_emit="true"
+			;;
 		--target)
 			shift
 			target="$1"
@@ -139,6 +144,7 @@ function tsconfig() {
         "isolatedModules": $isolated_modules,
         "sourceMap": $source_map,
         "declaration": $declaration,
+        "noEmit": $no_emit,
         "target": "$target",
         "moduleResolution": "$module_resolution",
         "traceResolution": $trace_resolution,
@@ -161,6 +167,9 @@ function ts_project() {
 	local source_map=""
 	local declaration=""
 	local composite=""
+	local transpiler=""
+	local mock_transpiler_disabled="#"
+	local no_emit=""
 	while (($# > 0)); do
 		case "$1" in
 		--path)
@@ -215,6 +224,15 @@ function ts_project() {
 			shift
 			composite="composite = True,"
 			;;
+		--transpiler-mock)
+			shift;
+			transpiler="transpiler = mock,"
+			mock_transpiler_disabled=""
+			;;
+		--no-emit)
+			shift
+			no_emit="no_emit = True,"
+			;;
 		--)
 			shift
 			break
@@ -238,6 +256,7 @@ function ts_project() {
 load("@aspect_rules_ts//ts:defs.bzl", "ts_project")
 ${npm_link_all_packages}load("@npm//:defs.bzl", "npm_link_all_packages")
 ${npm_link_all_packages}npm_link_all_packages(name = "node_modules")
+${mock_transpiler_disabled}load("@aspect_rules_ts//ts/test:mock_transpiler.bzl", "mock")
 
 ts_project(
     name = "${name}",
@@ -250,6 +269,8 @@ ts_project(
     $source_map
     $declaration
     $composite
+    $transpiler
+    $no_emit
 )
 EOF
 }

e2e/test/validation.bats

@@ -0,0 +1,38 @@
+load "common.bats"
+
+setup() {
+    cd $BATS_FILE_TMPDIR
+}
+
+teardown() {
+    bazel shutdown
+    rm -rf $BATS_FILE_TMPDIR/*
+}
+
+
+@test 'When tsc is only used for type-checking with a type-error, should pass when validations are disabled' {
+    workspace
+
+    echo "export const a: string = 1;" > ./source.ts
+    tsconfig --declaration
+    ts_project --transpiler-mock --declaration --src "source.ts"
+
+    run bazel build :foo --norun_validations
+    assert_success
+    run cat bazel-bin/source.js
+    assert_success
+    # Mock transpiler just copies source input to output
+    assert_output -p 'export const a: string = 1;'
+}
+
+@test 'When tsc is only used for type-checking with a type-error, should fail when validations are enabled' {
+    workspace
+
+    echo "export const a: string = 1;" > ./source.ts
+    tsconfig --no-emit
+    ts_project --no-emit --src "source.ts"
+
+    run bazel build :foo --run_validations
+    assert_failure
+    assert_output -p "error TS2322: Type 'number' is not assignable to type 'string'"
+}

examples/no_emit/BUILD.bazel

@@ -0,0 +1,20 @@
+load("@aspect_rules_ts//ts:defs.bzl", "ts_project")
+load("@bazel_skylib//rules:write_file.bzl", "write_file")
+
+write_file(
+    name = "gen_ts",
+    out = "a.ts",
+    content = [
+        "export const a: number = 42",
+    ],
+)
+
+# Shows how to run `tsc` producing no outputs at all.
+# It will use a validation action to type-check the file:
+# https://bazel.build/extending/rules#validation_actions
+# Run bazel with --norun_validations to skip type-checking.
+ts_project(
+    name = "typecheck_only",
+    srcs = ["a.ts"],
+    no_emit = True,
+)

examples/no_emit/tsconfig.json

@@ -0,0 +1,7 @@
+{
+    // Workaround https://github.com/microsoft/TypeScript/issues/59036
+    "exclude": [],
+    "compilerOptions": {
+        "noEmit": true
+    }
+}

examples/transpiler/BUILD.bazel

@@ -29,3 +29,19 @@ ts_project(
     source_map = True,
     transpiler = babel,
 )
+
+# Runs babel to transpile ts -> js
+# and does not produce any declaration outputs.
+# `tsc` is used for type-check only, as a validation action
+# (run bazel with --norun_validations to skip typechecking)
+ts_project(
+    name = "no-emit",
+    srcs = ["big.ts"],
+    no_emit = True,
+    transpiler = babel,
+    tsconfig = {
+        "compilerOptions": {
+            "noEmit": True,
+        },
+    },
+)

examples/typecheck_only/BUILD.bazel

@@ -1,22 +1,19 @@
 """Only type-checks the input file, but does no transpilation or output any typings files.
 
-As such, it cannot run as a Bazel action under `bazel build`, as Bazel will only run actions when
-their outputs are requested.
-
-Therefore this is a test target and should be run with `bazel test`.
+Therefore type-checking is done with a validation action within the `ts_project` rule.
 """
 
-load("@npm//examples:typescript/package_json.bzl", "bin")
+load("@aspect_rules_ts//ts:defs.bzl", "ts_project")
 
-bin.tsc_test(
+ts_project(
     name = "typecheck_only",
-    args = [
-        "--noEmit",
-        "$(location check-me.ts)",
+    srcs = [
+        "check-me.ts",
+        "lib.js",
     ],
-    data = ["check-me.ts"],
-    # It should fail because we made a typing mistake
-    # TypeScript ReturnCode:
-    # OutputGeneratedWithErrors = 2,      // .js and .map generated with semantic errors
-    expected_exit_code = 2,
+    tsconfig = {
+        "compilerOptions": {
+            "noEmit": True,
+        },
+    },
 )

examples/typecheck_only/check-me.ts

@@ -1 +1,2 @@
-const a: number = 'a-string'
+// Ensure importing from .js works
+export * from './lib'

examples/typecheck_only/lib.js

@@ -0,0 +1 @@
+export const a = 42

ts/defs.bzl

@@ -47,6 +47,7 @@ def ts_project(
         preserve_jsx = False,
         composite = False,
         incremental = False,
+        no_emit = False,
         emit_declaration_only = False,
         transpiler = None,
         ts_build_info_file = None,
@@ -215,6 +216,8 @@ def ts_project(
             Instructs Bazel to expect a `.tsbuildinfo` output and a `.d.ts` output for each `.ts` source.
         incremental: Whether the `incremental` bit is set in the tsconfig.
             Instructs Bazel to expect a `.tsbuildinfo` output.
+        no_emit: Whether the `noEmit` bit is set in the tsconfig.
+            Instructs Bazel *not* to expect any outputs. Only a validation action is used.
         emit_declaration_only: Whether the `emitDeclarationOnly` bit is set in the tsconfig.
             Instructs Bazel *not* to expect `.js` or `.js.map` outputs for `.ts` sources.
         ts_build_info_file: The user-specified value of `tsBuildInfoFile` from the tsconfig.
@@ -276,6 +279,7 @@ def ts_project(
         source_map = compiler_options.setdefault("sourceMap", source_map)
         declaration = compiler_options.setdefault("declaration", declaration)
         declaration_map = compiler_options.setdefault("declarationMap", declaration_map)
+        no_emit = compiler_options.setdefault("noEmit", no_emit)
         emit_declaration_only = compiler_options.setdefault("emitDeclarationOnly", emit_declaration_only)
         allow_js = compiler_options.setdefault("allowJs", allow_js)
         if resolve_json_module != None:
@@ -309,14 +313,14 @@ def ts_project(
     typings_out_dir = declaration_dir if declaration_dir else out_dir
     tsbuildinfo_path = ts_build_info_file if ts_build_info_file else name + ".tsbuildinfo"
 
-    tsc_typings_outs = _lib.calculate_typings_outs(srcs, typings_out_dir, root_dir, declaration, composite, allow_js)
-    tsc_typing_maps_outs = _lib.calculate_typing_maps_outs(srcs, typings_out_dir, root_dir, declaration_map, allow_js)
+    tsc_typings_outs = _lib.calculate_typings_outs(srcs, typings_out_dir, root_dir, declaration, composite, allow_js, no_emit)
+    tsc_typing_maps_outs = _lib.calculate_typing_maps_outs(srcs, typings_out_dir, root_dir, declaration_map, allow_js, no_emit)
 
     tsc_js_outs = []
     tsc_map_outs = []
-    if not transpiler or transpiler == "tsc":
-        tsc_js_outs = _lib.calculate_js_outs(srcs, out_dir, root_dir, allow_js, resolve_json_module, preserve_jsx, emit_declaration_only)
-        tsc_map_outs = _lib.calculate_map_outs(srcs, out_dir, root_dir, source_map, preserve_jsx, emit_declaration_only)
+    if no_emit or not transpiler or transpiler == "tsc":
+        tsc_js_outs = _lib.calculate_js_outs(srcs, out_dir, root_dir, allow_js, resolve_json_module, preserve_jsx, no_emit, emit_declaration_only)
+        tsc_map_outs = _lib.calculate_map_outs(srcs, out_dir, root_dir, source_map, preserve_jsx, no_emit, emit_declaration_only)
         tsc_target_name = name
     else:
         # To stitch together a tree of ts_project where transpiler is a separate rule,
@@ -401,6 +405,7 @@ def ts_project(
         typings_outs = tsc_typings_outs,
         typing_maps_outs = tsc_typing_maps_outs,
         buildinfo_out = tsbuildinfo_path if composite or incremental else None,
+        no_emit = no_emit,
         emit_declaration_only = emit_declaration_only,
         tsc = tsc,
         tsc_worker = tsc_worker,

ts/private/ts_lib.bzl

@@ -114,6 +114,9 @@ COMPILER_OPTION_ATTRS = {
     "declaration_map": attr.bool(
         doc = "https://www.typescriptlang.org/tsconfig#declarationMap",
     ),
+    "no_emit": attr.bool(
+        doc = "https://www.typescriptlang.org/tsconfig#noEmit",
+    ),
     "emit_declaration_only": attr.bool(
         doc = "https://www.typescriptlang.org/tsconfig#emitDeclarationOnly",
     ),
@@ -234,8 +237,8 @@ def _validate_tsconfig_dirs(root_dir, out_dir, typings_out_dir):
     if typings_out_dir and typings_out_dir.find("../") != -1:
         fail("typings_out_dir cannot output to parent directory")
 
-def _calculate_js_outs(srcs, out_dir, root_dir, allow_js, resolve_json_module, preserve_jsx, emit_declaration_only):
-    if emit_declaration_only:
+def _calculate_js_outs(srcs, out_dir, root_dir, allow_js, resolve_json_module, preserve_jsx, no_emit, emit_declaration_only):
+    if no_emit or emit_declaration_only:
         return []
 
     exts = {
@@ -253,8 +256,8 @@ def _calculate_js_outs(srcs, out_dir, root_dir, allow_js, resolve_json_module, p
 
     return _to_js_out_paths(srcs, out_dir, root_dir, allow_js, resolve_json_module, exts)
 
-def _calculate_map_outs(srcs, out_dir, root_dir, source_map, preserve_jsx, emit_declaration_only):
-    if not source_map or emit_declaration_only:
+def _calculate_map_outs(srcs, out_dir, root_dir, source_map, preserve_jsx, no_emit, emit_declaration_only):
+    if no_emit or not source_map or emit_declaration_only:
         return []
 
     exts = {
@@ -269,8 +272,8 @@ def _calculate_map_outs(srcs, out_dir, root_dir, source_map, preserve_jsx, emit_
 
     return _to_js_out_paths(srcs, out_dir, root_dir, False, False, exts)
 
-def _calculate_typings_outs(srcs, typings_out_dir, root_dir, declaration, composite, allow_js):
-    if not (declaration or composite):
+def _calculate_typings_outs(srcs, typings_out_dir, root_dir, declaration, composite, allow_js, no_emit):
+    if no_emit or not (declaration or composite):
         return []
 
     exts = {
@@ -283,8 +286,8 @@ def _calculate_typings_outs(srcs, typings_out_dir, root_dir, declaration, compos
 
     return _to_js_out_paths(srcs, typings_out_dir, root_dir, allow_js, False, exts)
 
-def _calculate_typing_maps_outs(srcs, typings_out_dir, root_dir, declaration_map, allow_js):
-    if not declaration_map:
+def _calculate_typing_maps_outs(srcs, typings_out_dir, root_dir, declaration_map, allow_js, no_emit):
+    if no_emit or not declaration_map:
         return []
 
     exts = {