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Misc. Notes on WebPerl
======================


Links
-----

Other places I've written about WebPerl:

- [Run Perl 5 in the Browser!](https://www.perlmonks.org/?node_id=1220426)
- [WebPerl Regex Tester (beta)](https://www.perlmonks.org/?node_id=1221705)
- [Embedding WebPerl Code Demos into Other Pages](https://www.perlmonks.org/?node_id=1223812)
- [WebPerl now has Experimental Perl 6 Support!](https://www.perlmonks.org/?node_id=1225647)

### Talks

- YAPC::EU 2019 (PerlCon) in Rīga - [talk](https://perlcon.eu/talk/40), [slides](https://goo.gl/QPvUb9) ([PDF](HD_WebPerl_Riga_2019_Slides.pdf)), [Video Link](https://youtu.be/bT17TCMbsdc)
  - Bonus Lightning Talk - [Video Link](https://youtu.be/tenl6JEum5k?t=29642)
- German Perl Workshop 2019 in Munich - [talk](http://act.yapc.eu/gpw2019/talk/7616), [slides in English](https://goo.gl/yM6dff) ([PDF](HD_WebPerl_GPW_2019_Slides.pdf)), talk in German 🇩🇪, [Video Link](https://www.youtube.com/watch?v=EI8js5zf_Pw)
- YAPC::EU 2018 in Glasgow - [lightning talk](http://act.perlconference.org/tpc-2018-glasgow/talk/7475), [Video Link](https://youtu.be/KrGSg7uVZj0?t=29520)

[![DOI 10.5281/zenodo.1400490](https://zenodo.org/badge/DOI/10.5281/zenodo.1400490.svg)](https://doi.org/10.5281/zenodo.1400490)

### "In the Press"

- WebPerl gets another mention in Will Braswell's talk ["The Perl Family Tree: Discover Your Heritage"](https://www.youtube.com/watch?v=ZM-KHZJpy84) at The Perl Conference 2019 in Pittsburgh
- WebPerl gets a mention in Will Braswell's talk ["Perl 11 - The Future of Saint Larry's Language"](https://fosdem.org/2019/schedule/event/perl11/) at FOSDEM '19
- [Perl Advent Calendar 2018, Day 2](http://www.perladvent.org/2018/2018-12-02.html) (by Mark Fowler)
- [Reddit: Your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should (2018-10-22)](https://www.reddit.com/r/programmingcirclejerk/comments/9qerw5/your_scientists_were_so_preoccupied_with_whether/) 😉
- [Hacker News (2018-10-21)](https://news.ycombinator.com/item?id=18269071)
- [Reddit /r/programming (2018-10-21)](https://www.reddit.com/r/programming/comments/9q65tf/run_perl_in_the_browser_with_webperl/)
- [Facebook Group "Perl Programmers" (2018-10-20)](https://www.facebook.com/groups/perlprogrammers/permalink/2141844605848316/)
- [Reddit /r/perl: WebPerl Regex Tester (2018-09-05)](https://www.reddit.com/r/perl/comments/9d5n77/webperl_regex_tester/)

### Prior Art

Several people have built microperl with Emscripten:

- Harsha <https://github.com/moodyharsh/plu>
- Shlomi Fish <https://github.com/shlomif/perl5-for-JavaScript--take2>
- FUJI Goro <https://github.com/gfx/perl.js>


TODOs
-----

1. Testing
	
	- How to best disable individual tests that we know won't work? (qx etc.)
	- How to handle the many tests that call an external Perl?
		- patching t/test.pl's runperl() seems easiest at the moment, and we can use the iframe method from the IDE
	- Continue work on `WebPerl.t`
		- More tests for Unicode support (Perl/JS interface, Perl.eval(), plus Emscripten's virtual FS)
	- Focus on getting the tests running in the browser instead of node.js
	- How to best package tests?
		- If possible, a separate bundle, so that it can be loaded optionally and we don't need to rebuild
		- How does `make test` find and handle all the various modules' `t`s?

2. Misc
	
	- Write up a full RPC example
	- `Future`
		- Would `Future::AsyncAwait` work in WebPerl? (Or maybe with a JS backend?)
		- `Future::HTTP` (probably just as a frontend to XHR?)
	- Improve Perl 6 integration
		- Build a packaged Rakudo.js ourselves instead of borrowing from <https://perl6.github.io/6pad/>
		- Perhaps get an API change or two into Rakudo.js: `STDOUT` currently gets output with HTML escapes
		- See also notes in [Perl 6 Support 🦋](perl6.html)
	- Investigate Emscripten's main loop concept for handling nonblocking sockets?
	- Use Multiplicity for re-starting perl? (Thanks to Nick Clark for the idea)
	- Add Regex::Debugger into regex tester? (Thanks to Renee for the idea)
	- Turn some patches from emperl5 into patches for P5P
	- Submit some patches to Emscripten
		- <https://github.com/kripken/emscripten/pull/7005>
		- <https://github.com/kripken/emscripten/issues/7029>
		- Would we need to patch Perl's signal functions if Emscripten's stubs weren't noisy?
	- Add `Perl.Util` functions for making file uploads and downloads easier
		- Plus an example showing how to use it to run a "legacy" Perl script with inputs and output
	- There is some potential for restructuring:
		- `Perl.glue()` and `Perl.dispatch()` could go into `WebPerl.xs` (?)
		- Parts of `webperl.js` could go into `common_preamble.js` or `WebPerl.xs`,
		  so that `emperl.js` is **runnable on its own in a Web Worker (?)**
		  (see notes in `perlrunner.html` / `e12f1aa25a000`)
		  → this might be interesting for running tests?!
		- `nodeperl_dev_prerun.js` could probably be merged into that as well
	- Could put a `WebPerl` stub on CPAN
		- In theory could write a `WebPerl::Local` that contains the `WebPerl` API, and
		  have various drivers such as `WebPerl::WebDriver` or `WebPerl::JSAny` that
		  runs the code given to WebPerl's `js()`...
	- Regarding the funky syntax highlighting on GitHub: <https://github.com/atom/language-html/issues/88#issuecomment-431361414>

3. See Also
	
	- <https://github.com/haukex/webperl/issues>
	- <https://github.com/haukex/webperl/pulls>
	- See also `TODO`s in the source tree by grepping for `TODO`
	  or using the included `findtodo.sh`.


SSL
---

	$ openssl req -x509 -nodes -days 365 -newkey rsa:2048 -keyout selfsigned.key -out selfsigned.crt
	...
	Common Name (e.g. server FQDN or YOUR name) []: localhost
	...
	$ plackup --enable-ssl --ssl-key-file=selfsigned.key --ssl-cert-file=selfsigned.crt web/webperl.psgi
	# then go to https://localhost:5000 and accept the certificate warning

Possible Improvements
---------------------

- More efficient JS/C/Perl glue
- Test/Support sockets/WebSockets
	- for example, can we compile a DBD:: module to connect to a DB on the server?
- A RPC module for communicating between client and server Perls
	- I think it's probably best to not have WebPerl prescribe a specific RPC mechanism,
	  since there's a big variety and many are pretty simple to implement using e.g. jQuery
- Support some of the Emscripten C API (like wget?)
- Try to shrink the download size more (exclude more modules, ...?)


Limitations
-----------

- Only works in browsers with WebAssembly support
  (asm.js requires aligned memory access, and Perl apparently has quite a few places with unaligned access)
- 32-bit ints
- No `system`, `qx`, `fork`, `kill`, `wait`, `waitpid`, threads, etc.
	- Theoretically, we could link in BusyBox to get a shell and utilities (??)
	- (`system` and `qx` support could theoretically be added by patching `pp_system`/`pp_backtick` in `pp_sys.c`)
- No signals (except `SIGALRM`)
- In the current configuration, `exit` is not supported, and therefore `atexit` handlers aren't supported
  (see discussion in [Using WebPerl](using.html), and `NO_EXIT_RUNTIME` in the Emscripten documentation -
  currently it seems to make the most sense to build with `NO_EXIT_RUNTIME=1`)
- Static linking, requires rebuild to add modules
  (Emscripten apparently only supports asm.js dynamic linking when dynamic memory growth is disabled, which is not very useful)


Release Checklist
-----------------

- Update `Changes.md` with all changes since last release
  
  As an example, to list changes since a specific version, excluding the regex tester:
  
      $ git log --stat v0.05-beta.. -- . ':!web/regex_tester.html' ':!.gitignore'
  
	- Also make sure that the documentation in `using.md` etc. mentions when features were added/deprecated

- Update version numbers everywhere; use `grep` to find them, for example:
  
      $ grep -Er --exclude-dir=hostperl --exclude-dir=.git --exclude-dir=emperl5 --exclude=emperl.* '0\.[01][0-9]' .
      $ ( cd emperl5; grep -Er '0\.[01][0-9]' `git diff --numstat --diff-filter=ACMRT v5.28.1 HEAD | cut -f3` )
  
  At a minimum there is:
	- `web/webperl.js` - `Perl.WebPerlVersion`
	- `emperl5/ext/WebPerl/lib/WebPerl.pm` - `$VERSION`
	- `pages/index.md` and `pages/using.md` - download links

- Update [Subresource Integrity](https://developer.mozilla.org/en-US/docs/Web/Security/Subresource_Integrity) values as needed, e.g.:
  
      $ perl -wMstrict -MDigest::SRI=sri -le 'print sri "SHA-256","web/webperl.js"'

- Build and create dist, e.g. `build/build.pl --reconfig --dist=webperl_prebuilt_v0.07-beta`

- Test all build results, both from `file://...` and `http://localhost`

- Add tags, the `webperl` repo gets an annotated tag such as `v0.07-beta`,
  and the `emperl5` repo gets an unannotated tag such as `webperl_v0.07-beta`,
  then `git push --tags`

- Create a release on GitHub and upload the `webperl_prebuilt_*.zip` as an asset

- Uploading to AWS S3:
	1. `for X in emperl.* webperl.js; do gzip -v -9 $X && mv -v $X.gz $X ; done`
	2. Upload them with the appropriate `Content-Type` (see e.g. `web/webperl.psgi`) and a `Content-Encoding` of `gzip`

- If there was a `pages_for_vX.XX` branch of `gh-pages`, don't forget to merge that


***

Copyright (c) 2018 Hauke Daempfling (haukex@zero-g.net)
at the Leibniz Institute of Freshwater Ecology and Inland Fisheries (IGB),
Berlin, Germany, <http://www.igb-berlin.de>

Please see the ["Legal" page](legal.html) for details.

***

You can find the source for this page at
<https://github.com/haukex/webperl/blob/gh-pages/notes.md>

