tools: allow single JS file for --link-module

The description for the --link-module configuration option is as
follows:
$ ./configure --help | grep -A 5 'link-module'
  --link-module=LINKED_MODULE
                      Path to a JS file to be bundled in the binary as a
                      builtin. This module will be referenced by path
                      without extension; e.g. /root/x/y.js will be
                      referenced via require('root/x/y'). Can be used
                      multiple times

This lead me to think that it was possible to specify a file like this:
$ ./configure --link-module=something.js
$ NODE_DEBUG=mkcodecache make -j8

This will lead to a compilation error as an entry in the source_ map in
node_javascript.cc will end up having an empty string as its key:
source_.emplace("", UnionBytes{_raw, 105});

This will then be used by CodeCacheBuilder when it iterates over the
module ids, which will lead to the following compilation errors:

/node/out/Release/obj/gen/node_code_cache.cc:12:23: warning:
ISO C++17 does not allow a decomposition group to be
empty [-Wempty-decomposition]
static const uint8_t [] = {
                      ^
/node/out/Release/obj/gen/node_code_cache.cc:12:22: warning:
decomposition declarations are a C++17 extension [-Wc++17-extensions]
static const uint8_t [] = {
                     ^~
/node/out/Release/obj/gen/node_code_cache.cc:12:1: error:
decomposition declaration cannot be declared 'static'
static const uint8_t [] = {
^~~~~~
/node/out/Release/obj/gen/node_code_cache.cc:12:22: error:
decomposition declaration cannot be declared with type 'const uint8_t'
(aka 'const unsigned char'); declared type must be 'auto' or
reference to 'auto'
static const uint8_t [] = {
                     ^
/node/out/Release/obj/gen/node_code_cache.cc:12:22: error:
excess elements in scalar initializer
static const uint8_t [] = {
                     ^
/node/out/Release/obj/gen/node_code_cache.cc:660:7: error:
expected expression
      ,
      ^
/node/out/Release/obj/gen/node_code_cache.cc:661:24: error:
no matching function for call to 'arraysize'
      static_cast<int>(arraysize()), policy
                       ^~~~~~~~~
../src/util.h:667:18: note: candidate function template not viable:
requires 1 argument, but 0 were provided
constexpr size_t arraysize(const T (&)[N]) {
                 ^
2 warnings and 5 errors generated.

This commit suggests that passing a single file be allowed by modifying
tools/js2c.py.

PR-URL: https://github.com/nodejs/node/pull/28443
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>

1 files changed, 2 insertions, 1 deletions

diff --git a/tools/js2c.py b/tools/js2c.py
index 0189dd7629..1346b2a870 100755
--- a/tools/js2c.py
+++ b/tools/js2c.py
@@ -261,7 +261,8 @@ def NormalizeFileName(filename):
     split = ['internal'] + split
   else:  # `lib/**/*.js` so drop the 'lib' part
     split = split[1:]
-  filename = '/'.join(split)
+  if len(split):
+    filename = '/'.join(split)
   return os.path.splitext(filename)[0]