ESM-and-CJS-butting-heads.sh

# this gist is an appendix for the discussion in this article:
# https://medium.com/@osherel/yet-another-look-on-js-require-and-import-e2a6316a161d

#Some setup:
mkdir -p sandbox/packages/a sandbox/packages/c;
cd sandbox;
echo '{"name":"sandbox","version":"1.0.0","workspaces":["packages/*"]}' > package.json;
npm init -y -w -q packages/a;
npm init -y -w -q packages/c;
echo 'export default "a"' > packages/a/index.js;
echo "exports.foo = 'bar'" > packages/c/index.js;
sed -i s/index.js/index.mjs/ packages/a/package.json;

#----------------------------------------------------------------------------------------------
# requiring a single trivial module
cat packages/c/index.js
# yields: exports.foo = 'bar'
 
#in node:
start = process.hrtime.bigint(); require('c'); Number(process.hrtime.bigint() - start) / 1e6

#----------------------------------------------------------------------------------------------
# lets do that in big numbers:
{
  I=0; while [ $I -ne 500 ]; do
    mkdir -p packages/req$I;
    npm init -y -q -w packages/req${I} > /dev/null 2>&1;
    echo  "require('req$(($I + 1))')" > packages/req${I}/index.js;
    [ 0 = $(((I += 1) % 10)) ] && echo -n "$I ";
  done
  echo "require('node:fs')" > packages/req499/index.js;
}

node -p "start = process.hrtime.bigint(); require('req0'); Number(process.hrtime.bigint() - start) / 1e6"
node -p "start = process.hrtime.bigint(); require('req0'); Number(process.hrtime.bigint() - start) / 1e6"
node -p "start = process.hrtime.bigint(); require('req0'); Number(process.hrtime.bigint() - start) / 1e6"

echo "require('node:fs')" > packages/req249/index.js; 

node -p "start = process.hrtime.bigint(); require('req0'); Number(process.hrtime.bigint() - start) / 1e6"
node -p "start = process.hrtime.bigint(); require('req0'); Number(process.hrtime.bigint() - start) / 1e6"
node -p "start = process.hrtime.bigint(); require('req0'); Number(process.hrtime.bigint() - start) / 1e6"

echo "require('node:fs')" > packages/req99/index.js; 

node -p "start = process.hrtime.bigint(); require('req0'); Number(process.hrtime.bigint() - start) / 1e6"
node -p "start = process.hrtime.bigint(); require('req0'); Number(process.hrtime.bigint() - start) / 1e6"
node -p "start = process.hrtime.bigint(); require('req0'); Number(process.hrtime.bigint() - start) / 1e6"

#----------------------------------------------------------------------------------------------
# importing a single trivial module
cat packages/a/index.mjs
# yields: export default "a"

#in node shell:
start = process.hrtime.bigint(); await import('a'); Number(process.hrtime.bigint() - start) / 1e6

#----------------------------------------------------------------------------------------------
# lets do that in big numbers
# this is a 500 deep linerar dependency tree
rm -rf packages/imp* node_modules/imp* packages/req* node_modules/req*
{
  I=0; while [ $I -ne 500 ]; do
    mkdir -p packages/imp${I};
    npm init -y -q -w packages/imp${I} > /dev/null 2>&1;
    sed -i s/index.js/index.mjs/ packages/imp${I}/package.json;
    echo  "import 'imp$(($I + 1))'" > packages/imp${I}/index.mjs;
    [ 0 = $(((I += 1) % 10)) ] && echo -n "$I ";
  done
  echo "import 'node:fs'" > packages/imp499/index.mjs;
}

#in node shell:
start = process.hrtime.bigint(); await import('imp0'); Number(process.hrtime.bigint() - start) / 1e6

echo "import 'node:fs'" > packages/imp249/index.mjs;

node -p "start = process.hrtime.bigint(); import('imp0').then(() => console.log(Number(process.hrtime.bigint() - start) / 1e6))"


echo "import 'node:fs'" > packages/imp99/index.mjs;

node -p "start = process.hrtime.bigint(); import('imp0').then(() => console.log(Number(process.hrtime.bigint() - start) / 1e6))"

#----------------------------------------------------------------------------------------------
# convert the experiment to a flat 1-generation graph with 499 dependencies
{
rm packages/imp0/index.mjs
I=1; while [ $I -ne 499 ]; do
    mkdir -p packages/imp${I};
    echo  "export default 'imp${I}'" > packages/imp${I}/index.mjs;
    [ 0 = "$I" ] || echo  "import 'imp$(($I + 1))'" >> packages/imp0/index.mjs;
    [ 0 = $(((I += 1) % 10)) ] && echo -n "$I ";
  done
  echo "import 'node:fs'" > packages/imp499/index.mjs;
}

node -p "start = process.hrtime.bigint(); import('imp0').then(() => console.log(Number(process.hrtime.bigint() - start) / 1e6))"

#----------------------------------------------------------------------------------------------
# circular dependency
{#circular
mkdir -p packages/l1 packages/l2 packages/l3;
for I in 1 2 3; do
  npm init -w packages/l$I -y > /dev/null 2<&1;
  sed -i s/index.js/index.mjs/ packages/l$I/package.json;
  N=$(( $I % 3 + 1 ))
  echo "import l$N from 'l$N'; export default l$N;" > packages/l$I/index.mjs;
  echo -n "$I ";
done;
}
node -e "import('l1').then(() => console.log('done'))" 
# this fails


# and making it work
{#circular-test
mkdir -p packages/l1 packages/l2 packages/l3;
for I in 1 2 3; do
  npm init -w packages/l$I -y > /dev/null 2<&1;
  sed -i s/index.js/index.mjs/ packages/l$I/package.json;
  N=$(( $I % 3 + 1 ))
  echo "import * as l$N from 'l$N'; console.log('init $I'); export default l$N;" > packages/l$I/index.mjs;
  echo -n "$I ";
done;
}

node -e "import('l1').then(() => console.log('done'))" 
# this works