feat(typescript): generate tsconfig.json for ts_project

This is an experimental, opt-in feature where ts_project will generate a tsconfig.json file in place of
the user specifying one in the source directory.

I expect a long tail of compatibility bugs since any path appearing in this generated file needs to point from
bazel-out back to the source directory.

Fixes bazel-contrib#2058

packages/typescript/checked_in_ts_project.bzl

@@ -1,7 +1,6 @@
 "checked_in_ts_project rule"
 
 load("@build_bazel_rules_nodejs//:index.bzl", "generated_file_test")
-load("@build_bazel_rules_nodejs//third_party/github.com/bazelbuild/bazel-skylib:rules/write_file.bzl", "write_file")
 load("//packages/typescript:index.bzl", "ts_project")
 
 def checked_in_ts_project(name, src, checked_in_js = None, **kwargs):
@@ -15,16 +14,13 @@ def checked_in_ts_project(name, src, checked_in_js = None, **kwargs):
     if not checked_in_js:
         checked_in_js = src[:-3] + ".js"
 
-    tsconfig = "tsconfig_%s.json" % name
-
-    # workspace is up three dirs (bazel-out/arch/bin) plus number of segments in the package
-    workspace_root = "/".join([".."] * (3 + len(native.package_name().split("/"))))
-
-    # Generate a tsconfig, this is partly an example of how it can be done, per jbedard and toxicable request
-    write_file(
-        name = "_gen_tsconfig_%s" % name,
-        content = [struct(
-            compilerOptions = struct(
+    ts_project(
+        name = name,
+        srcs = [src],
+        declaration = True,
+        # using config means a tsconfig.json file will be generated
+        config = {
+            "compilerOptions": struct(
                 lib = ["es2017", "dom"],
                 strict = True,
                 target = "es2015",
@@ -33,16 +29,7 @@ def checked_in_ts_project(name, src, checked_in_js = None, **kwargs):
                 declaration = True,
                 skipLibCheck = True,
             ),
-            files = ["/".join([workspace_root, native.package_name(), src])],
-        ).to_json()],
-        out = tsconfig,
-    )
-
-    ts_project(
-        name = name,
-        srcs = [src],
-        declaration = True,
-        tsconfig = tsconfig,
+        },
         **kwargs
     )
 

packages/typescript/internal/ts_config.bzl

@@ -14,6 +14,8 @@
 
 "tsconfig.json files using extends"
 
+load("@build_bazel_rules_nodejs//third_party/github.com/bazelbuild/bazel-skylib:rules/write_file.bzl", "write_file")
+
 TsConfigInfo = provider()
 
 def _ts_config_impl(ctx):
@@ -46,3 +48,21 @@ feature from TypeScript, then the Bazel implementation needs to know about that
 extended configuration file as well, to pass them both to the TypeScript compiler.
 """,
 )
+
+def _join(*elements):
+    return "/".join([f for f in elements if f])
+
+# Syntax sugar around skylib's write_file
+def write_tsconfig(name, config, files, out):
+    # workspace is up three dirs (bazel-out/arch/bin) plus number of segments in the package
+    workspace_root = "/".join([".."] * (3 + len(native.package_name().split("/"))))
+
+    amended_config = struct(
+        files = [_join(workspace_root, native.package_name(), f) for f in files],
+        **config
+    )
+    write_file(
+        name = name,
+        content = [amended_config.to_json()],
+        out = out,
+    )

packages/typescript/internal/ts_project.bzl

@@ -2,6 +2,7 @@
 
 load("@build_bazel_rules_nodejs//:providers.bzl", "DeclarationInfo", "NpmPackageInfo", "declaration_info", "js_module_info", "run_node")
 load("@build_bazel_rules_nodejs//internal/linker:link_node_modules.bzl", "module_mappings_aspect")
+load(":ts_config.bzl", "write_tsconfig")
 
 _DEFAULT_TSC = (
     # BEGIN-INTERNAL
@@ -226,6 +227,7 @@ def _out_paths(srcs, outdir, rootdir, ext):
 def ts_project_macro(
         name = "tsconfig",
         tsconfig = None,
+        config = None,
         srcs = None,
         args = [],
         deps = [],
@@ -349,6 +351,13 @@ def ts_project_macro(
 
         deps: List of labels of other rules that produce TypeScript typings (.d.ts files)
 
+        config: EXPERIMENTAL a dictionary of tsconfig keys.
+
+            If specified, a tsconfig.json file will be generated for this compilation.
+            You may use only one of config or tsconfig
+
+            Each file in srcs will be converted to a relative path in the `files` section.
+
         tsconfig: Label of the tsconfig.json file to use for the compilation.
 
             By default, we add `.json` to the `name` attribute.
@@ -400,26 +409,40 @@ def ts_project_macro(
 
     if srcs == None:
         srcs = native.glob(["**/*.ts", "**/*.tsx"])
-
-    if tsconfig == None:
-        tsconfig = name + ".json"
-
     extra_deps = []
 
-    if validate:
-        validate_options(
-            name = "_validate_%s_options" % name,
-            target = "//%s:%s" % (native.package_name(), name),
-            declaration = declaration,
-            source_map = source_map,
-            declaration_map = declaration_map,
-            composite = composite,
-            incremental = incremental,
-            emit_declaration_only = emit_declaration_only,
-            tsconfig = tsconfig,
-            extends = extends,
+    if config != None:
+        # Usage with a config attribute that generates a tsconfig.json
+        if tsconfig != None:
+            fail("only one of config or tsconfig may be set")
+
+        tsconfig = "tsconfig_%s.json" % name
+        write_tsconfig(
+            name = "_gen_tsconfig_%s" % name,
+            config = config,
+            files = srcs,
+            out = tsconfig,
         )
-        extra_deps.append("_validate_%s_options" % name)
+
+    else:
+        # Usage with a user-defined tsconfig.json file
+        if tsconfig == None:
+            tsconfig = name + ".json"
+
+        if validate:
+            validate_options(
+                name = "_validate_%s_options" % name,
+                target = "//%s:%s" % (native.package_name(), name),
+                declaration = declaration,
+                source_map = source_map,
+                declaration_map = declaration_map,
+                composite = composite,
+                incremental = incremental,
+                emit_declaration_only = emit_declaration_only,
+                tsconfig = tsconfig,
+                extends = extends,
+            )
+            extra_deps.append("_validate_%s_options" % name)
 
     typings_out_dir = declaration_dir if declaration_dir else out_dir
 

packages/typescript/test/ts_project/generated_tsconfig/BUILD.bazel

@@ -0,0 +1,32 @@
+load("@build_bazel_rules_nodejs//:index.bzl", "generated_file_test")
+load("//packages/typescript:index.bzl", "ts_project")
+
+ts_project(
+    name = "compile1",
+    srcs = glob(["*.ts*"]),
+    config = {},
+    out_dir = "1",
+)
+
+generated_file_test(
+    name = "test1",
+    src = "empty_config.js_",
+    generated = ":1/a.js",
+)
+
+ts_project(
+    name = "compile2",
+    srcs = glob(["*.ts*"]),
+    config = {
+        "compilerOptions": {
+            "module": "esnext",
+        },
+    },
+    out_dir = "2",
+)
+
+generated_file_test(
+    name = "test2",
+    src = "esnext.js_",
+    generated = ":2/a.js",
+)

packages/typescript/test/ts_project/generated_tsconfig/a.ts

@@ -0,0 +1 @@
+export const a: string = 'hello world';

packages/typescript/test/ts_project/generated_tsconfig/empty_config.js_

@@ -0,0 +1,3 @@
+"use strict";
+exports.__esModule = true;
+exports.a = 'hello world';

packages/typescript/test/ts_project/generated_tsconfig/esnext.js_

@@ -0,0 +1 @@
+export var a = 'hello world';