Node.js errors when running emconfigure ./configure when there exists a package.json with type: "module"

[jeremy-code]

Version

emscripten/[email protected]

# emcc -v
emcc (Emscripten gcc/clang-like replacement + linker emulating GNU ld) 4.0.8 (70404efec4458b60b953bc8f1529f2fa112cdfd1)
clang version 21.0.0git (https:/github.com/llvm/llvm-project 23e3cbb2e82b62586266116c8ab77ce68e412cf8)
Target: wasm32-unknown-emscripten
Thread model: posix
InstalledDir: /emsdk/upstream/bin

# node -v
v20.18.0
# which node
/emsdk/node/20.18.0_64bit/bin/node

Description

Suppose you had the following files: configure.ac, dummy.c, and package.json. (Note: this is true even if package.json is not in the root directory, only such that the nearest package.json to cwd has type: module.)

# configure.ac
AC_INIT([dummy], [0.1])
AC_CONFIG_SRCDIR([dummy.c])
AC_PROG_CC
AC_OUTPUT

// dummy.c
int x = 20;

{
  // package.json
  "type": "module"
}

Failing command line in full:

autoreconf && emconfigure ./configure (or any variation that uses autoconf)

Terminal output:

configure: ./configure
checking for gcc... /emsdk/upstream/emscripten/emcc
checking whether the C compiler works... yes
checking for C compiler default output file name... a.out
checking for suffix of executables... 
checking whether we are cross compiling... configure: error: in `/src':
configure: error: cannot run C compiled programs.
If you meant to cross compile, use `--host'.
See `config.log' for more details
emconfigure: error: './configure' failed (returned 77)

Snippet of output of config.log (full output here: https://pastebin.com/mWuRPrUP, or with EMCC_DEBUG=1 here: https://pastebin.com/aDECYhHk)

# config.log
...
configure:2721: checking whether we are cross compiling
configure:2729: /emsdk/upstream/emscripten/emcc -o conftest    conftest.c  >&5
configure:2733: $? = 0
configure:2740: ./conftest
file:///src/conftest:79
  var fs = require('fs');
           ^

ReferenceError: require is not defined in ES module scope, you can use import instead
    at file:///src/conftest:79:12
    at ModuleJob.run (node:internal/modules/esm/module_job:234:25)
    at async ModuleLoader.import (node:internal/modules/esm/loader:473:24)
    at async asyncRunEntryPointWithESMLoader (node:internal/modules/run_main:123:5)

Node.js v20.18.0
configure:2744: $? = 1
configure:2751: error: in `/src':
configure:2753: error: cannot run C compiled programs.
If you meant to cross compile, use `--host'.

Indeed, if you remove the type: module from package.json, config.log will look like this:

configure:2721: checking whether we are cross compiling
configure:2729: /emsdk/upstream/emscripten/emcc -o conftest    conftest.c  >&5
configure:2733: $? = 0
configure:2740: ./conftest
configure:2744: $? = 0
configure:2759: result: no
configure:2764: checking for suffix of object files

and a.wasm, config.status will be generated.

In regards to conftest, this is the the output of /emsdk/upstream/emscripten/emcc -o conftest conftest.c and conftest.c is

/* confdefs.h */
#define PACKAGE_NAME "dummy"
#define PACKAGE_TARNAME "dummy"
#define PACKAGE_VERSION "0.1"
#define PACKAGE_STRING "dummy 0.1"
#define PACKAGE_BUGREPORT ""
#define PACKAGE_URL ""
/* end confdefs.h.  */
#include <stdio.h>
int
main (void)
{
FILE *f = fopen ("conftest.out", "w");
 return ferror (f) || fclose (f) != 0;
 
  ;
  return 0;
}

I believe the reason this occurs is that a feature was added to automatically detect extensionless modules based on the nearest package.json in v21.0.0, and this was backported to 20.10.0. Setting --experimental-default-type=commonjs doesn't seem to fix it though.

I haven't found any solutions for this other than generating a package.json in the build directory with npm init --yes or deleting that type: "module".

[sbc100]

Yeah it kind of sucks that node doesn't support forcing commonjs from the command line.

I guess one possible solution would be to convert all configure tests to use .mjs and ES modules? Would using the .mjs extensions for ES module mode even if type: module were not in the package.json? i.e. does mjs force module mode?

[jeremy-code]

Yeah it kind of sucks that node doesn't support forcing commonjs from the command line.

I guess one possible solution would be to convert all configure tests to use .mjs and ES modules? Would using the .mjs extensions for ES module mode even if type: module were not in the package.json? i.e. does mjs force module mode?

Yeah, I'm empathetic that this issue isn't on Emscripten's end and is more of a quirk of Node.js. Personally, I'm fine with my solution of just running npm init --yes in any directories with a configure script since from what I can tell, while autodetecting module syntax is now unflagged (as of v22.7.0), it's still not recommended due to a bit of overhead and adding type: "module" to ES packages is still recommended.