build: add workaround for invalid imports generation in bazel

Applies a workaround for the invalid imports generation issue
in the Bazel `ng_module` rule. Read more about this here:

https://hackmd.io/@devversion/ryCOwIKIS.

Author: devversion

tools/bazel/postinstall-patches.js

@@ -49,3 +49,23 @@ shelljs.sed('-i', 'var indexFile;', `
 if (!shelljs.test('-f', 'node_modules/@angular/bazel/src/ng_package/rollup_bin.js')) {
   shelljs.cat(path.join(__dirname, './rollup_windows_arguments.patch')).exec('patch -p0');
 }
+
+// Workaround for: https://hackmd.io/MlqFp-yrSx-0mw4rD7dnQQ?both. We only want to discard
+// the metadata of files in the bazel managed node modules. That way we keep the default
+// behavior of ngc-wrapped except for dependencies between sources of the library. This makes
+// the "generateCodeForLibraries" flag more accurate in the Bazel environment where previous
+// compilations should not be treated as external libraries. Read more about this in the document.
+shelljs.sed('-i', /if \((this\.options\.generateCodeForLibraries === false)/,
+  `if (filePath.includes('node_modules/') && $1`,
+  'node_modules/@angular/compiler-cli/src/transformers/compiler_host.js');
+// The three replacements below ensure that metadata files can be read by NGC and
+// that metadata files are collected as Bazel action inputs.
+shelljs.sed('-i', /(const NGC_ASSETS = \/[^(]+\()([^)]*)(\).*\/;)/, '$1$2|metadata.json$3',
+  'node_modules/@angular/bazel/src/ngc-wrapped/index.js');
+shelljs.sed('-i', /^((\s*)results = depset\(dep.angular.summaries, transitive = \[results]\))$/,
+  `$1#\n$2results = depset(dep.angular.metadata, transitive = [results])`,
+  'node_modules/@angular/bazel/src/ng_module.bzl');
+shelljs.sed('-i',
+  /^((\s*)results = depset\(target.angular.summaries if hasattr\(target, "angular"\) else \[]\))$/,
+  `$1#\n$2results = depset(target.angular.metadata if hasattr(target, "angular") else [], transitive = [results])`,
+  'node_modules/@angular/bazel/src/ng_module.bzl');

tools/defaults.bzl

@@ -6,8 +6,8 @@ load("@npm_bazel_karma//:defs.bzl", _karma_web_test_suite = "karma_web_test_suit
 load("@npm_bazel_protractor//:index.bzl", _protractor_web_test_suite = "protractor_web_test_suite")
 load("@npm_bazel_typescript//:defs.bzl", _ts_library = "ts_library")
 load("//:packages.bzl", "ANGULAR_LIBRARY_UMDS", "VERSION_PLACEHOLDER_REPLACEMENTS")
-load("//tools/markdown-to-html:index.bzl", _markdown_to_html = "markdown_to_html")
 load("//tools:default_module_name.bzl", "get_default_module_name")
+load("//tools/markdown-to-html:index.bzl", _markdown_to_html = "markdown_to_html")
 
 _DEFAULT_TSCONFIG_BUILD = "//src:bazel-tsconfig-build.json"
 _DEFAULT_TSCONFIG_TEST = "//src:tsconfig-test"
@@ -44,13 +44,32 @@ def ts_library(tsconfig = None, deps = [], testonly = False, **kwargs):
         **kwargs
     )
 
-def ng_module(deps = [], tsconfig = None, module_name = None, testonly = False, **kwargs):
+def ng_module(
+        deps = [],
+        srcs = [],
+        tsconfig = None,
+        module_name = None,
+        flat_module_out_file = None,
+        testonly = False,
+        **kwargs):
     if not tsconfig:
         tsconfig = _getDefaultTsConfig(testonly)
 
     if not module_name and not testonly:
         module_name = get_default_module_name()
 
+    if module_name and not flat_module_out_file:
+        flat_module_out_file = "index"
+
+    # Workaround to avoid a lot of changes to the Bazel build rules. Since
+    # for most targets the flat module out file is "index.js", we cannot
+    # include "index.ts" (if present) as source-file. This would resolve
+    # in a conflict in the metadata bundler. Once we switch to Ivy and
+    # no longer need metadata bundles, we can remove this logic.
+    if flat_module_out_file == "index":
+        if "index.ts" in srcs:
+            srcs.remove("index.ts")
+
     local_deps = [
         # Add tslib because we use import helpers for all public packages.
         "@npm//tslib",
@@ -67,8 +86,10 @@ def ng_module(deps = [], tsconfig = None, module_name = None, testonly = False,
             local_deps = local_deps + [d]
 
     _ng_module(
+        srcs = srcs,
         type_check = _ENABLE_NG_TYPE_CHECKING,
         module_name = module_name,
+        flat_module_out_file = flat_module_out_file,
         deps = local_deps,
         tsconfig = tsconfig,
         testonly = testonly,