build: Auto-load ICU data from --with-icu-default-data-dir

configure.py

@@ -450,6 +450,14 @@
         'the icu4c source archive. '
         'v%d.x or later recommended.' % icu_versions['minimum_icu'])
 
+intl_optgroup.add_option('--with-icu-default-data-dir',
+    action='store',
+    dest='with_icu_default_data_dir',
+    help='Path to the icuXXdt{lb}.dat file. If unspecified, ICU data will '
+         'only be read if the NODE_ICU_DATA environment variable or the '
+         '--icu-data-dir runtime argument is used. This option has effect '
+         'only when Node.js is built with --with-intl=small-icu.')
+
 parser.add_option('--with-ltcg',
     action='store_true',
     dest='with_ltcg',
@@ -1391,6 +1399,7 @@ def write_config(data, name):
     locs.add('root')  # must have root
     o['variables']['icu_locales'] = ','.join(str(loc) for loc in locs)
     # We will check a bit later if we can use the canned deps/icu-small
+    o['variables']['icu_default_data'] = options.with_icu_default_data_dir or ''
   elif with_intl == 'full-icu':
     # full ICU
     o['variables']['v8_enable_i18n_support'] = 1

node.gypi

@@ -103,6 +103,13 @@
       'conditions': [
         [ 'icu_small=="true"', {
           'defines': [ 'NODE_HAVE_SMALL_ICU=1' ],
+          'conditions': [
+            [ 'icu_default_data!=""', {
+              'defines': [
+                'NODE_ICU_DEFAULT_DATA_DIR="<(icu_default_data)"',
+              ],
+            }],
+          ],
       }]],
     }],
     [ 'node_no_browser_globals=="true"', {

src/node.cc

@@ -90,6 +90,7 @@
 
 #if defined(NODE_HAVE_I18N_SUPPORT)
 #include <unicode/uvernum.h>
+#include <unicode/utypes.h>
 #endif
 
 
@@ -882,6 +883,25 @@ int InitializeNodeWithArgs(std::vector<std::string>* argv,
   if (per_process::cli_options->icu_data_dir.empty())
     credentials::SafeGetenv("NODE_ICU_DATA",
                             &per_process::cli_options->icu_data_dir);
+
+#ifdef NODE_ICU_DEFAULT_DATA_DIR
+  // If neither the CLI option nor the environment variable was specified,
+  // fall back to the configured default
+  if (per_process::cli_options->icu_data_dir.empty()) {
+    // Check whether the NODE_ICU_DEFAULT_DATA_DIR contains the right data
+    // file and can be read.
+    static const char full_path[] =
+        NODE_ICU_DEFAULT_DATA_DIR "/" U_ICUDATA_NAME ".dat";
+
+    FILE* f = fopen(full_path, "rb");
+
+    if (f != nullptr) {
+      fclose(f);
+      per_process::cli_options->icu_data_dir = NODE_ICU_DEFAULT_DATA_DIR;
+    }
+  }
+#endif  // NODE_ICU_DEFAULT_DATA_DIR
+
   // Initialize ICU.
   // If icu_data_dir is empty here, it will load the 'minimal' data.
   if (!i18n::InitializeICUDirectory(per_process::cli_options->icu_data_dir)) {