Accepts JS sources in prerender_component() and a js_library() as…

… a scripts dependency.

This chooses to generate either a `ts_library()` or `js_library()` based on the sources provided to `prerender_component()`. Whatever is given, is re-exported via `js_reexport()` which propagates both `JSModuleInfo` and `JSEcmaScriptModuleInfo`. This needs to be custom because `js_library()` only returns `JSModuleInfo` while `ts_library()` returns both, but a `js_library()` that depends on a `ts_library()` will drop its dependency's `JSEcmaScriptModuleInfo`, meaning there is no clean way of re-exporting a target which may be a `js_library()` or a `ts_library()`.

common/BUILD.bazel

@@ -3,6 +3,7 @@ load("@npm//@bazel/typescript:index.bzl", "ts_library")
 load("//tools:jasmine.bzl", "jasmine_node_test")
 load("//tools:publish.bzl", "publish_files")
 load(":label_test.bzl", "label_test_suite")
+load(":paths_test.bzl", "paths_test_suite")
 
 publish_files(
     name = "publish_files",
@@ -118,6 +119,20 @@ bzl_library(
 
 label_test_suite(name = "label_test")
 
+bzl_library(
+    name = "paths",
+    srcs = ["paths.bzl"],
+    visibility = ["//visibility:public"],
+)
+
+bzl_library(
+    name = "paths_test_lib",
+    srcs = ["paths_test.bzl"],
+    deps = [":paths"],
+)
+
+paths_test_suite(name = "paths_test")
+
 ts_library(
     name = "runfiles",
     srcs = ["runfiles.ts"],

common/paths.bzl

@@ -0,0 +1,5 @@
+"""Utilities based around file paths."""
+
+def is_js_file(src):
+    """Returns whether or not the given src path is a JavaScript file."""
+    return src.endswith(".js") or src.endswith(".mjs") or src.endswith(".cjs")

common/paths_test.bzl

@@ -0,0 +1,22 @@
+"""Tests for `paths.bzl`."""
+
+load("@bazel_skylib//lib:unittest.bzl", "asserts", "unittest")
+load(":paths.bzl", "is_js_file")
+
+def _is_js_file_impl(ctx):
+    env = unittest.begin(ctx)
+
+    asserts.equals(env, True, is_js_file("foo/bar/baz.js"))
+    asserts.equals(env, True, is_js_file("foo/bar/baz.mjs"))
+    asserts.equals(env, True, is_js_file("foo/bar/baz.cjs"))
+
+    asserts.equals(env, False, is_js_file("foo/bar/baz.ts"))
+    asserts.equals(env, False, is_js_file("foo/bar/baz.d.ts"))
+    asserts.equals(env, False, is_js_file("foo/bar/baz.test"))
+
+    return unittest.end(env)
+
+_is_js_file_test = unittest.make(_is_js_file_impl)
+
+def paths_test_suite(name):
+    unittest.suite(name, _is_js_file_test)

examples/custom_bundling/BUILD.bazel

@@ -33,7 +33,9 @@ ts_library(
 # Manually bundle all scripts.
 rollup_bundle(
     name = "bundle",
-    entry_point = ":page_scripts.ts",
+    # TODO: Need to use `_esm_sources()` to pick out the `.mjs` file and depend
+    # on it directly.
+    entry_point = ":page_scripts.mjs",
     config_file = "rollup.config.js",
     link_workspace_root = True,
     silent = True,

packages/rules_prerender/BUILD.bazel

@@ -64,6 +64,7 @@ bzl_library(
     deps = [
         ":web_resources",
         "//common:label",
+        "//common:paths",
     ],
 )
 
@@ -96,6 +97,7 @@ bzl_library(
     visibility = ["//:__pkg__"],
     deps = [
         ":web_resources",
+        "//common:paths",
         "//packages/renderer:build_vars",
     ],
 )

packages/rules_prerender/prerender_component.bzl

@@ -1,7 +1,14 @@
 """Defines `prerender_component()` functionality."""
 
+load("@build_bazel_rules_nodejs//:index.bzl", "js_library")
+load(
+    "@build_bazel_rules_nodejs//:providers.bzl",
+    "JSModuleInfo",
+    "JSEcmaScriptModuleInfo",
+)
 load("@npm//@bazel/typescript:index.bzl", "ts_library")
 load("//common:label.bzl", "absolute")
+load("//common:paths.bzl", "is_js_file")
 load(":web_resources.bzl", "web_resources")
 
 def prerender_component(
@@ -31,11 +38,14 @@ def prerender_component(
     
     Args:
         name: The name of this rule.
-        srcs: The TypeScript source files for use in prerendering.
+        srcs: The source files for use in prerendering. May be `*.ts` files or
+            `*.js`/`*.mjs`/`*.cjs`. All source files must be JavaScript, or all
+            source files must be TypeScript. However, mixing the two is not
+            allowed. `*.d.ts` files are also allowed in either case.
         tsconfig: A label referencing a tsconfig.json file or `ts_config()`
-            target. Will be used to compile files in `srcs`.
+            target. Will be used to compile `*.ts` files in `srcs`.
         data: See https://docs.bazel.build/versions/master/be/common-definitions.html.
-        lib_deps: `ts_library()` dependencies for the TypeScript source files.
+        lib_deps: Dependencies for the source files.
         scripts: List of client-side JavaScript libraries which can be included
             in the prerendered HTML.
         styles: List of CSS files or `filegroup()`s of CSS files which can be
@@ -66,26 +76,42 @@ def prerender_component(
     """
 
     prerender_lib = "%s_prerender" % name
-    ts_library(
-        name = prerender_lib,
-        srcs = srcs,
-        tsconfig = tsconfig,
-        data = data,
-        deps = lib_deps + ["%s_prerender" % absolute(dep) for dep in deps],
-        testonly = testonly,
-        visibility = visibility,
-    )
+    if all([src.endswith(".ts") or src.endswith(".d.ts") for src in srcs]):
+        ts_library(
+            name = prerender_lib,
+            srcs = srcs,
+            tsconfig = tsconfig,
+            data = data + styles,
+            deps = lib_deps + ["%s_prerender" % absolute(dep) for dep in deps],
+            testonly = testonly,
+            visibility = visibility,
+        )
+    elif all([is_js_file(src) or src.endswith(".d.ts") for src in srcs]):
+        js_library(
+            name = prerender_lib,
+            srcs = srcs + data + styles, # `data` is included in `srcs`.
+            deps = lib_deps + ["%s_prerender" % absolute(dep) for dep in deps],
+            testonly = testonly,
+            visibility = visibility,
+        )
+    else:
+        fail(" ".join("""
+All sources must be TypeScript (`*.ts`) or all sources must be JavaScript
+(`*.js` / `*.mjs` / `*.cjs`). It is not possible to use some JavaScript sources
+and some TypeScript sources in the same component (excluding `*.d.ts` files,
+which are always allowed).
+        """.strip().split("\n")))
 
     native.alias(
         name = "%s_prerender_for_test" % name,
         actual = ":%s" % prerender_lib,
         testonly = True,
     )
 
-    ts_library(
+    js_reexport(
         name = "%s_scripts" % name,
-        srcs = [],
-        deps = scripts + ["%s_scripts" % absolute(dep) for dep in deps],
+        srcs = scripts,
+        deps = ["%s_scripts" % absolute(dep) for dep in deps],
         testonly = testonly,
         visibility = visibility,
     )
@@ -103,3 +129,72 @@ def prerender_component(
         visibility = visibility,
         deps = resources + ["%s_resources" % absolute(dep) for dep in deps],
     )
+
+def _js_reexport_impl(ctx):
+    # TODO
+    # for dep in ctx.attr.deps:
+    #     if JSEcmaScriptModuleInfo in dep:
+    #         print("%s - %s" % (ctx.label, dep[JSEcmaScriptModuleInfo]))
+    js_srcs = [src for src in ctx.files.srcs if is_js_file(src.path)]
+
+    merged_js_module_info = JSModuleInfo(
+        direct_sources = depset(js_srcs,
+            transitive = [src[JSModuleInfo].direct_sources
+                          for src in ctx.attr.srcs
+                          if JSModuleInfo in src],
+        ),
+        sources = depset(js_srcs,
+            transitive = [dep[JSModuleInfo].sources
+                          for dep in ctx.attr.srcs + ctx.attr.deps
+                          if JSModuleInfo in dep],
+        ),
+    )
+
+    merged_js_ecma_script_module_info = JSEcmaScriptModuleInfo(
+        direct_sources = depset(js_srcs,
+            transitive = [src[JSEcmaScriptModuleInfo].direct_sources
+                          for src in ctx.attr.srcs
+                          if JSEcmaScriptModuleInfo in src],
+        ),
+        sources = depset(js_srcs,
+            transitive = [dep[JSEcmaScriptModuleInfo].sources
+                          for dep in ctx.attr.srcs + ctx.attr.deps
+                          if JSEcmaScriptModuleInfo in dep],
+        ),
+    )
+
+    # TODO: Remove
+    output_group_info = OutputGroupInfo(
+        js_module_info_direct_sources = depset(js_srcs,
+            transitive = [src[JSModuleInfo].direct_sources
+                          for src in ctx.attr.srcs
+                          if JSModuleInfo in src],
+        ),
+        js_ecma_script_module_info_direct_sources = depset(js_srcs,
+            transitive = [src[JSEcmaScriptModuleInfo].direct_sources
+                          for src in ctx.attr.srcs
+                          if JSEcmaScriptModuleInfo in src],
+        ),
+    )
+
+    return [
+        merged_js_module_info,
+        merged_js_ecma_script_module_info,
+        output_group_info,
+    ]
+
+# TODO: Rename? It's not really a reexport?
+# TODO: Move to own file?
+js_reexport = rule(
+    implementation = _js_reexport_impl,
+    attrs = {
+        "srcs": attr.label_list(
+            default = [],
+            allow_files = True,
+        ),
+        "deps": attr.label_list(
+            mandatory = True,
+            providers = [JSModuleInfo],
+        ),
+    },
+)

packages/rules_prerender/prerender_pages.bzl

@@ -1,5 +1,10 @@
 """Defines `prerender_pages()` functionality."""
 
+load(
+    "@build_bazel_rules_nodejs//:providers.bzl",
+    "JSEcmaScriptModuleInfo",
+    "JSModuleInfo",
+)
 load("@npm//@bazel/postcss:index.bzl", "postcss_binary")
 load("@npm//@bazel/rollup:index.bzl", "rollup_bundle")
 load(":multi_inject_resources.bzl", "multi_inject_resources")
@@ -122,18 +127,24 @@ def prerender_pages(
         testonly = True,
     )
 
+    _esm_sources(
+        name = "%s_scripts" % name,
+        dep = "%s_scripts" % prerender_name,
+        testonly = testonly,
+    )
+
     bundle = "%s_bundle" % name
     if bundle_js:
         # Bundle all client-side scripts at `%{name}_bundle.js`.
         rollup_bundle(
             name = bundle,
-            entry_point = ":%s_scripts.ts" % prerender_name,
+            entry_point = ":%s_scripts" % name,
             config_file = "//packages/rules_prerender:rollup-default.config.js",
             link_workspace_root = True,
             silent = True,
             testonly = testonly,
             deps = [
-                ":%s_scripts" % prerender_name,
+                ":%s_scripts" % name,
                 "@npm//@rollup/plugin-node-resolve",
             ],
         )
@@ -175,3 +186,33 @@ def prerender_pages(
             ":%s_resources" % prerender_name,
         ],
     )
+
+def _esm_sources_impl(ctx):
+    providers = []
+
+    # Propagate providers of dependencies.
+    if JSEcmaScriptModuleInfo in ctx.attr.dep:
+        providers.append(ctx.attr.dep[JSEcmaScriptModuleInfo])
+    if JSModuleInfo in ctx.attr.dep:
+        providers.append(ctx.attr.dep[JSModuleInfo])
+
+    # Use direct sources as `DefaultInfo`, prefering `JSEcmaScriptModuleInfo`.
+    if JSEcmaScriptModuleInfo in ctx.attr.dep:
+        providers.append(DefaultInfo(
+            files = ctx.attr.dep[JSEcmaScriptModuleInfo].direct_sources,
+        ))
+    elif JSModuleInfo in ctx.attr.dep:
+        providers.append(
+            DefaultInfo(files = ctx.attr.dep[JSModuleInfo].direct_sources),
+        )
+    else:
+        fail("Dependency (%s) does provides neither JSEcmaScriptModuleInfo nor JSModuleInfo. It must provide at least one." % ctx.attr.dep.label)
+
+    return providers
+
+_esm_sources = rule(
+    implementation = _esm_sources_impl,
+    attrs = {
+        "dep": attr.label(mandatory = True),
+    },
+)

packages/rules_prerender/prerender_pages_unbundled.bzl

@@ -1,10 +1,10 @@
 """Defines `prerender_pages_unbundled()` functionality."""
 
-load("@build_bazel_rules_nodejs//:index.bzl", "nodejs_binary")
+load("@build_bazel_rules_nodejs//:index.bzl", "js_library", "nodejs_binary")
 load("@npm//@bazel/typescript:index.bzl", "ts_library")
 load("//common:label.bzl", "absolute", "file_path_of")
 load(":entry_points.bzl", "script_entry_point", "style_entry_point")
-load(":prerender_component.bzl", "prerender_component")
+load(":prerender_component.bzl", "prerender_component", "js_reexport")
 load(":prerender_resources.bzl", "prerender_resources")
 load(":web_resources.bzl", "WebResourceInfo", "web_resources")
 
@@ -58,9 +58,9 @@ def prerender_pages_unbundled(
     Outputs:
         %{name}: A `web_resources()` target containing all the files generated
             by the `src` file at their corresponding locations.
-        %{name}_scripts: A `ts_library()` rule containing all the client-side
+        %{name}_scripts: A `js_library()` rule containing all the client-side
             scripts used by the page. This includes a generated file
-            `%{name}_scripts.ts` which acts as an entry point, importing all
+            `%{name}_scripts.js` which acts as an entry point, importing all
             scripts that were included in the page via `includeScript()`.
         %{name}_styles: A `filegroup()` containing all the CSS styles used by
             the page.
@@ -116,7 +116,11 @@ def prerender_pages_unbundled(
 
     # Execute the runner to generate annotated resources.
     annotated = "%s_annotated" % name
-    js_src = ".ts".join(src.split(".ts")[:-1]) + ".js"
+    js_src = (
+        ".ts".join(src.split(".ts")[:-1]) + ".js"
+        if src.endswith(".ts")
+        else src
+    )
     prerender_resources(
         name = annotated,
         entry_point = file_path_of(absolute(js_src)),
@@ -136,7 +140,7 @@ def prerender_pages_unbundled(
 
     # Generate the entry point importing all included scripts.
     client_scripts = "%s_scripts" % name
-    script_entry = "%s.ts" % client_scripts
+    script_entry = "%s.js" % client_scripts
     script_entry_point(
         name = "%s_entry" % client_scripts,
         metadata = metadata,
@@ -145,7 +149,7 @@ def prerender_pages_unbundled(
     )
 
     # Reexport all included scripts at `%{name}_scripts`.
-    ts_library(
+    js_reexport(
         name = client_scripts,
         srcs = [script_entry],
         deps = [":%s" % component_scripts],

packages/rules_prerender/prerender_resources.bzl

@@ -1,6 +1,7 @@
 """Defines `prerender_resources()` functionality."""
 
 load("@build_bazel_rules_nodejs//:index.bzl", "nodejs_binary")
+load("//common:paths.bzl", "is_js_file")
 load("//packages/renderer:build_vars.bzl", "RENDERER_RUNTIME_DEPS")
 load(":web_resources.bzl", "WebResourceInfo")
 
@@ -60,7 +61,7 @@ def prerender_resources(
         visibility: See https://docs.bazel.build/versions/master/be/common-definitions.html.
     """
     # Validate `entry_point`.
-    if "/" not in entry_point or not entry_point.endswith(".js"):
+    if "/" not in entry_point or not is_js_file(entry_point):
         fail(("`entry_point` (%s) *must* be a workspace-relative path of the"
                 + " format: \"path/to/pkg/file.js\"") % entry_point)