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 #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):
@@ -15,34 +14,20 @@ 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(
-                lib = ["es2017", "dom"],
-                strict = True,
-                target = "es2015",
-                module = "commonjs",
-                removeComments = True,
-                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,
+        tsconfig = {
+            "compilerOptions": {
+                "declaration": True,
+                "lib": ["es2017", "dom"],
+                "module": "commonjs",
+                "removeComments": True,
+                "skipLibCheck": True,
+                "strict": True,
+                "target": "es2015",
+            },
+        },
         **kwargs
     )
 

packages/typescript/internal/ts_config.bzl

@@ -55,3 +55,79 @@ 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])
+
+def _relative_path(tsconfig_path, dest):
+    if dest.is_source:
+        # Calculate a relative path from the directory where we're writing the tsconfig
+        # back to the sources root
+        workspace_root = "/".join([".."] * len(tsconfig_path.dirname.split("/")))
+        return _join(workspace_root, dest.path)
+
+    # TODO: basename isn't exactly correct, there could be a subdir
+    return dest.basename
+
+def _write_tsconfig_rule(ctx):
+    # TODO: is it useful to expand Make variables in the content?
+    content = "\n".join(ctx.attr.content)
+    if ctx.attr.extends:
+        content = content.replace(
+            "__extends__",
+            _relative_path(ctx.outputs.out, ctx.file.extends),
+        )
+    if ctx.attr.files:
+        content = content.replace(
+            "\"__files__\"",
+            str([_relative_path(ctx.outputs.out, f) for f in ctx.files.files]),
+        )
+    ctx.actions.write(
+        output = ctx.outputs.out,
+        content = content,
+    )
+    return [DefaultInfo(files = depset([ctx.outputs.out]))]
+
+write_tsconfig_rule = rule(
+    implementation = _write_tsconfig_rule,
+    attrs = {
+        "content": attr.string_list(),
+        "extends": attr.label(allow_single_file = True),
+        "files": attr.label_list(allow_files = True),
+        "out": attr.output(),
+    },
+)
+
+# Syntax sugar around skylib's write_file
+def write_tsconfig(name, config, files, extends, out):
+    """Wrapper around bazel_skylib's write_file which understands tsconfig paths
+
+    Args:
+        name: name of the resulting write_file rule
+        config: tsconfig dictionary
+        files: list of input .ts files to put in the files[] array
+        extends: a tsconfig.json file to extend from
+        out: the file to write
+    """
+
+    # Allow extends to be a list of labels, as this is what ts_project accepts
+    if type(extends) == type([]):
+        if len(extends):
+            extends = extends[0]
+        else:
+            extends = None
+    if extends:
+        extends = Label(extends)
+        config["extends"] = "__extends__"  #_join(workspace_root, extends.package, extends.name)
+
+    amended_config = struct(
+        files = "__files__",  #[_join(workspace_root, native.package_name(), f) for f in files],
+        **config
+    )
+    write_tsconfig_rule(
+        name = name,
+        files = files,
+        extends = extends,
+        content = [amended_config.to_json()],
+        out = out,
+    )

packages/typescript/internal/ts_project.bzl

@@ -2,7 +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", "TsConfigInfo")
+load(":ts_config.bzl", "TsConfigInfo", "write_tsconfig")
 
 _DEFAULT_TSC = (
     # BEGIN-INTERNAL
@@ -39,11 +39,22 @@ _OUTPUTS = {
 }
 
 def _join(*elements):
-    return "/".join([f for f in elements if f])
+    segments = [f for f in elements if f]
+    if len(segments):
+        return "/".join(segments)
+    return "."
 
 def _ts_project_impl(ctx):
     arguments = ctx.actions.args()
 
+    generated_srcs = False
+    for src in ctx.files.srcs:
+        if src.is_source:
+            if generated_srcs:
+                fail("srcs cannot be a mix of generated files and source files")
+        else:
+            generated_srcs = True
+
     # Add user specified arguments *before* rule supplied arguments
     arguments.add_all(ctx.attr.args)
 
@@ -53,7 +64,11 @@ def _ts_project_impl(ctx):
         "--outDir",
         _join(ctx.bin_dir.path, ctx.label.package, ctx.attr.out_dir),
         "--rootDir",
-        _join(ctx.label.package, ctx.attr.root_dir) if ctx.label.package else ".",
+        _join(
+            ctx.bin_dir.path if generated_srcs else None,
+            ctx.label.package,
+            ctx.attr.root_dir,
+        ),
     ])
     if len(ctx.outputs.typings_outs) > 0:
         declaration_dir = ctx.attr.declaration_dir if ctx.attr.declaration_dir else ctx.attr.out_dir
@@ -363,6 +378,35 @@ def ts_project_macro(
 
             By default, we assume the tsconfig file is named by adding `.json` to the `name` attribute.
 
+            EXPERIMENTAL: generated tsconfig
+
+            Instead of a label, you can pass a dictionary of tsconfig keys.
+
+            In this case, a tsconfig.json file will be generated for this compilation, in the following way:
+            - all top-level keys will be copied by converting the dict to json.
+              So `tsconfig = {"compilerOptions": {"declaration": True}}`
+              will result in a generated `tsconfig.json` with `{"compilerOptions": {"declaration": true}}`
+            - each file in srcs will be converted to a relative path in the `files` section.
+            - the `extends` attribute will be converted to a relative path
+
+            Note that you can mix and match attributes and compilerOptions properties, so these are equivalent:
+
+            ```
+            ts_project(
+                tsconfig = {
+                    "compilerOptions": {
+                        "declaration": True,
+                    },
+                },
+            )
+            ```
+            and
+            ```
+            ts_project(
+                declaration = True,
+            )
+            ```
+
         extends: List of labels of tsconfig file(s) referenced in `extends` section of tsconfig.
 
             Any tsconfig files "chained" by extends clauses must either be transitive deps of the TsConfigInfo
@@ -413,27 +457,58 @@ 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,
-            ts_build_info_file = ts_build_info_file,
-            tsconfig = tsconfig,
+    if type(tsconfig) == type(dict()):
+        # Copy attributes <-> tsconfig properties
+        # TODO: fail if compilerOptions includes a conflict with an attribute?
+        compiler_options = tsconfig.setdefault("compilerOptions", {})
+        source_map = compiler_options.setdefault("sourceMap", source_map)
+        declaration = compiler_options.setdefault("declaration", declaration)
+        declaration_map = compiler_options.setdefault("declarationMap", declaration_map)
+        emit_declaration_only = compiler_options.setdefault("emitDeclarationOnly", emit_declaration_only)
+
+        # These options are always passed on the tsc command line so don't include them
+        # in the tsconfig. At best they're redundant, but at worst we'll have a conflict
+        if "outDir" in compiler_options.keys():
+            out_dir = compiler_options.pop("outDir")
+        if "declarationDir" in compiler_options.keys():
+            declaration_dir = compiler_options.pop("declarationDir")
+        if "rootDir" in compiler_options.keys():
+            root_dir = compiler_options.pop("rootDir")
+
+        # FIXME: need to remove keys that have a None value?
+        write_tsconfig(
+            name = "_gen_tsconfig_%s" % name,
+            config = tsconfig,
+            files = srcs,
             extends = extends,
+            out = "tsconfig_%s.json" % name,
         )
-        extra_deps.append("_validate_%s_options" % name)
+
+        # From here, tsconfig becomes a file, the same as if the
+        # user supplied a tsconfig.json InputArtifact
+        tsconfig = "tsconfig_%s.json" % name
+
+    else:
+        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,
+                ts_build_info_file = ts_build_info_file,
+                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
     tsbuildinfo_path = ts_build_info_file if ts_build_info_file else name + ".tsbuildinfo"

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

@@ -0,0 +1,43 @@
+"Test that properties in the tsconfig dict are honored"
+
+load("@build_bazel_rules_nodejs//:index.bzl", "generated_file_test")
+load("//packages/typescript:index.bzl", "ts_project")
+
+ts_project(
+    tsconfig = {
+        "compilerOptions": {
+            "declaration": True,
+            "declarationDir": "types",
+            "declarationMap": True,
+            "module": "esnext",
+            "outDir": "out",
+            "rootDir": "src",
+            "sourceMap": True,
+            "types": [],
+        },
+    },
+)
+
+generated_file_test(
+    name = "test",
+    src = "expected.js_",
+    generated = ":out/a.js",
+)
+
+generated_file_test(
+    name = "test_map",
+    src = "expected.js.map_",
+    generated = ":out/a.js.map",
+)
+
+generated_file_test(
+    name = "test_dts",
+    src = "expected.d.ts_",
+    generated = ":types/a.d.ts",
+)
+
+generated_file_test(
+    name = "test_dtsmap",
+    src = "expected.d.ts.map_",
+    generated = ":types/a.d.ts.map",
+)

packages/typescript/test/ts_project/generated_tsconfig/config/expected.d.ts.map_

@@ -0,0 +1 @@
+{"version":3,"file":"a.d.ts","sourceRoot":"","sources":["../../../../../../../../../../packages/typescript/test/ts_project/generated_tsconfig/config/src/a.ts"],"names":[],"mappings":"AAAA,eAAO,MAAM,CAAC,EAAE,MAAsB,CAAC"}

packages/typescript/test/ts_project/generated_tsconfig/config/expected.d.ts_

@@ -0,0 +1,2 @@
+export declare const a: string;
+//# sourceMappingURL=a.d.ts.map

packages/typescript/test/ts_project/generated_tsconfig/config/expected.js.map_

@@ -0,0 +1 @@
+{"version":3,"file":"a.js","sourceRoot":"","sources":["../../../../../../../../../../packages/typescript/test/ts_project/generated_tsconfig/config/src/a.ts"],"names":[],"mappings":"AAAA,MAAM,CAAC,IAAM,CAAC,GAAW,aAAa,CAAC"}

packages/typescript/test/ts_project/generated_tsconfig/config/expected.js_

@@ -0,0 +1,2 @@
+export var a = 'hello world';
+//# sourceMappingURL=a.js.map

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

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

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

@@ -0,0 +1,43 @@
+"Test that attributes set on ts_project are honored"
+
+load("@build_bazel_rules_nodejs//:index.bzl", "generated_file_test")
+load("//packages/typescript:index.bzl", "ts_project")
+
+ts_project(
+    declaration = True,
+    declaration_dir = "types",
+    declaration_map = True,
+    out_dir = "out",
+    root_dir = "src",
+    source_map = True,
+    tsconfig = {
+        "compilerOptions": {
+            "module": "esnext",
+            "types": [],
+        },
+    },
+)
+
+generated_file_test(
+    name = "test",
+    src = "expected.js_",
+    generated = ":out/a.js",
+)
+
+generated_file_test(
+    name = "test_map",
+    src = "expected.js.map_",
+    generated = ":out/a.js.map",
+)
+
+generated_file_test(
+    name = "test_dts",
+    src = "expected.d.ts_",
+    generated = ":types/a.d.ts",
+)
+
+generated_file_test(
+    name = "test_dtsmap",
+    src = "expected.d.ts.map_",
+    generated = ":types/a.d.ts.map",
+)

packages/typescript/test/ts_project/generated_tsconfig/config_attrs/expected.d.ts.map_

@@ -0,0 +1 @@
+{"version":3,"file":"a.d.ts","sourceRoot":"","sources":["../../../../../../../../../../packages/typescript/test/ts_project/generated_tsconfig/config_attrs/src/a.ts"],"names":[],"mappings":"AAAA,eAAO,MAAM,CAAC,EAAE,MAAsB,CAAC"}