playwright/browser_patches/README.md
2021-10-18 12:21:02 -07:00

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- [Contributing Browser Patches](#Contributing-browser-patches)
* [1. Setting up local browser checkout](#1-setting-up-local-browser-checkout)
* [2. Developing a new change](#2-developing-a-new-change)
* [3. Exporting your change to playwright repo](#3-exporting-your-change-to-playwright-repo)
* [4. Rolling Playwright to the new browser build](#4-rolling-playwright-to-the-new-browser-build)
- [Cheatsheet](#cheatsheet)
* [Firefox](#firefox)
- [stack trace](#stack-trace)
- [logging](#logging)
* [WebKit](#webkit)
- [Debugging Windows](#degugging-windows)
- [Enable core dumps on Linux](#enable-core-dumps-on-linux)
# Contributing Browser Patches
Firefox and WebKit have additional patches atop to expose necessary capabilities.
Ideally, all these changes should be upstreamed.
For the time being, it is possible to setup a browser checkout
and develop from there.
[WebKit upstream status](webkit/upstream_status.md)
## 1. Setting up local browser checkout
From the `playwright` repo, run the following command:
```bash
$ ./browser_patches/prepare_checkout.sh firefox
```
(you can optionally pass "webkit" for a webkit checkout)
This will create a firefox checkout at `$HOME/firefox`
> **NOTE:** this command downloads GBs of data.
This command will:
- create a `browser_upstream` remote in the checkout
- create a `playwright-build` branch and apply all playwright-required patches to it.
## 2. Developing a new change
You want to create a new branch off the `playwright-build` branch.
Assuming that you're under `$HOME/firefox` checkout:
```bash
$ git checkout -b my-new-feature playwright-build
$ # develop my feature on the my-new-feature branch ....
```
## 3. Exporting your change to playwright repo
Once you're happy with the work you did in the browser-land, you want to export it to the `playwright` repo.
Assuming that you're in the root of the `playwright` repo and that your browser checkout has your feature branch checked out:
```bash
$ ./browser_patches/export.sh firefox
```
This script will:
- create a new patch and put it to the `./browser_patches/firefox/patches/`
- update the `./browser_patches/firefox/UPSTREAM_CONFIG.sh` if necessary
- bump the `./browser_patches/firefox/BUILD_NUMBER` number.
The script will assume Firefox checkout is located at `$HOME/firefox`
Send a PR to the Playwright repo to be reviewed.
## 4. Rolling Playwright to the new browser build
Once the patch has been committed, the build bots will kick in, compile and upload a new browser version to all the platforms. Then you can roll the browser:
```bash
$ node utils/roll_browser.js chromium 123456
```
# Cheatsheet
## See browser stdout/stderr
Set the `DEBUG=pw:browser` environment variable to see it.
## Firefox
### Debug build
When compiling set the `FF_DEBUG_BUILD=1` environment variable.
#### Stack trace
In `//mozglue/misc/StackWalk.cpp` add
```c++
#define MOZ_DEMANGLE_SYMBOLS 1
```
In native code use
```c++
#include "mozilla/StackWalk.h"
// ...
MozWalkTheStack(stderr);
```
If the stack trace is still mangled `cat` it to `tools/rb/fix_linux_stack.py`
#### Logging
Upstream documentation: https://developer.mozilla.org/en-US/docs/Mozilla/Developer_guide/Gecko_Logging
```bash
MOZ_LOG=nsHttp:5
```
Module name is a string passed to the `mozilla::LazyLogModule` of the corresponding component, e.g.:
```c++
LazyLogModule gHttpLog("nsHttp");
```
Inside Juggler, you can use `dump('foo\n')`.
## WebKit
#### Logging
Inside Objective-C you can use [NSLog](https://developer.apple.com/documentation/foundation/1395275-nslog).
```
NSLog(@"Foobar value: %@", value);
```
#### Debugging windows
In `Source\WTF\wtf\win\DbgHelperWin.cpp` replace
```#if !defined(NDEBUG)``` with ```#if 1```
Then regular `WTFReportBacktrace()` works.
#### Enable core dumps on Linux
```bash
mkdir -p /tmp/coredumps
sudo bash -c 'echo "/tmp/coredumps/core-pid_%p.dump" > /proc/sys/kernel/core_pattern'
ulimit -c unlimited
```
Then to read stack traces run the following command:
```bash
# To find out crashing process name
file core-pid_29652.dump
# Point gdb to the local binary of the crashed process and the core file
gdb $HOME/.cache/ms-playwright/webkit-1292/minibrowser-gtk/WebKitWebProcess core-pid_29652
# Inside gdb update .so library search path to the local one
set solib-search-path /home/yurys/.cache/ms-playwright/webkit-1292/minibrowser-gtk
# Finally print backtrace
bt
```