Stylo: replace product={gecko,servo} with engine={gecko,servo-2013,servo-2020}

[SimonSapin]

Renaming the variable helped make sure I looked at every use.

Also auto-generate relevant parts of CSSStyleDeclaration.webidl, to make libscript compile accordingly.

---

This change is 

[highfive]

Heads up! This PR modifies the following files:

• @wafflespeanut: python/servo/post_build_commands.py
• @emilio: components/style/properties/properties.mako.rs, components/style/properties/longhands/inherited_table.mako.rs, components/style/properties/longhands/outline.mako.rs, components/style/properties/longhands/box.mako.rs, components/style/properties/shorthands/font.mako.rs and 44 more

[highfive]

Warning

• These commits modify unsafe code. Please review it carefully!
• These commits modify style and layout code, but no tests are modified. Please consider adding a test!

[SimonSapin]

This still needs work in the script crate, to compile in --with-layout-2020 mode.

[emilio]

The new variable name makes more sense, too :)

This looks generally good, let me know when it's ready for a final look.

[emilio]

I was intentionally using remove() so that getting it wrong errored loud, fwiw...

[SimonSapin]

This is intended to catch a typo in the name, right?

My reasoning was that I don’t want to conditionally remove based on the engine, because we’d forget to edit this back when adding that property to the new layout engine.

I also tried not having a property exist at all before it is implemented in layout, but that’s already a lost cause: various parts of the style and script crate already refer to Rust APIs for specific APIs, so I used a pref to disable parsing instead. I’ll do the same here.

[emilio]

This logic reads backwards... You only parse it if it's unimplemented?

I assume that this is what you want and that that pref would always be false, but why making it a pref at all? You could just stash false here and use parse(condition = "not_servo_2020") or such, which would read a bit nicer?

[SimonSapin]

Oh yeah it’s totally backward :] Yes making it always false based on the build-time flag also works, but since there’s a pref for properties this felt more consistent.

[SimonSapin]

Wait no, it’s not backward. The layout logic for this value is unimplemented. We only parse the keyword if the “enable unimplemented syntax” pref is on. I’ve renamed to parse_unimplemented_in_servo_2020 to hopefully clarify.

This pref is basically never intended to be on, but prefs are what already had support in Mako template for disabling parsing of some properties while still generating a Rust type for their values.

[emilio]

Right, my point is that it reads backwards. I understand what it's doing, it just reads "parse if unimplemented_in_servo_2020", which is confusing, I think. Prefixing it with parse_ makes it a bit less confusing I guess.

[SimonSapin]

Alright, this is ready for landing now.

r? @nox for the WebIDL-related commit
r? @emilio for the Stylo-related commit in case you have thoughts, but feel free to delegate to @nox.

[jdm]

�[0m�[0m�[1m�[31merror:�[0m failed to run custom build command for `script v0.0.1 (/repo/components/script)`

Caused by:
  process didn't exit successfully: `/repo/target/debug/build/script-c748da99a214968c/build-script-build` (exit code: 101)
--- stderr
thread 'main' panicked at 'called `Result::unwrap()` on an `Err` value: Os { code: 2, kind: NotFound, message: "No such file or directory" }', src/libcore/result.rs:1051:5
stack backtrace:
   0: backtrace::backtrace::libunwind::trace
             at /cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.29/src/backtrace/libunwind.rs:88
   1: backtrace::backtrace::trace_unsynchronized
             at /cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.29/src/backtrace/mod.rs:66
   2: std::sys_common::backtrace::_print
             at src/libstd/sys_common/backtrace.rs:47
   3: std::sys_common::backtrace::print
             at src/libstd/sys_common/backtrace.rs:36
   4: std::panicking::default_hook::{{closure}}
             at src/libstd/panicking.rs:200
   5: std::panicking::default_hook
             at src/libstd/panicking.rs:214
   6: std::panicking::rust_panic_with_hook
             at src/libstd/panicking.rs:477
   7: std::panicking::continue_panic_fmt
             at src/libstd/panicking.rs:384
   8: rust_begin_unwind
             at src/libstd/panicking.rs:311
   9: core::panicking::panic_fmt
             at src/libcore/panicking.rs:85
  10: core::result::unwrap_failed
             at src/libcore/result.rs:1051
  11: core::result::Result<T,E>::unwrap
             at /rustc/273f42b5964c29dda2c5a349dd4655529767b07f/src/libcore/result.rs:852
  12: build_script_build::main
             at components/script/build.rs:21
  13: std::rt::lang_start::{{closure}}
             at /rustc/273f42b5964c29dda2c5a349dd4655529767b07f/src/libstd/rt.rs:64
  14: std::rt::lang_start_internal::{{closure}}
             at src/libstd/rt.rs:49
  15: std::panicking::try::do_call
             at src/libstd/panicking.rs:296
  16: __rust_maybe_catch_panic
             at src/libpanic_unwind/lib.rs:82
  17: std::panicking::try
             at src/libstd/panicking.rs:275
  18: std::panic::catch_unwind
             at src/libstd/panic.rs:394
  19: std::rt::lang_start_internal
             at src/libstd/rt.rs:48
  20: std::rt::lang_start
             at /rustc/273f42b5964c29dda2c5a349dd4655529767b07f/src/libstd/rt.rs:64
  21: main
  22: __libc_start_main
  23: _start
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

[SimonSapin]

Added a line in script/build.rs to create the $OUT_DIR/build/ directory before copying a file into it. In my local testing the directory was already there from an earlier build.

[nox]

LGTM, feel free to r=me.

[jdm]

@bors-servo r=nox

[bors-servo]

📌 Commit 2cc632e has been approved by nox

[bors-servo]

⌛ Testing commit 2cc632e with merge aa8b9fd...

[bors-servo]

💔 Test failed - status-taskcluster

[SimonSapin]

Removed the unused import, and removed the bit of unit test that runs a Python script that doesn’t exist anymore. (Kept the part where it check that the generated JSON file looks reasonable.)

@bors-servo r=nox

[bors-servo]

📌 Commit 0215d09 has been approved by nox

[bors-servo]

⌛ Testing commit 0215d09 with merge 8e7daa7...

[bors-servo]

☀️ Test successful - linux-rel-css, linux-rel-wpt, status-taskcluster
Approved by: nox
Pushing 8e7daa7 to master...