[#10461] Add docs about custom environment
minor #10470 [server:run] [#10461] Add docs about custom environment (WouterJ)

This PR was merged into the 2.3 branch.

Discussion
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[server:run] [#10461] Add docs about custom environment

| Q             | A
| ------------- | ---
| Fixed tickets | #10461, https://github.com/symfony/symfony-docs/issues/3688
| License       | MIT

It's better to document this specific usecase in the command help.

Commits
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6871a61 [#10461] Add docs about custom environment
fixed CS
[Process] Make Process::start non-blocking on Windows platform
[Process] Fix escaping on Windows

Windows escaping is broken since the last merges.
[Process] fixed fatal errors in getOutput and getErrorOutput when process was not started
bug #10420 [2.3][Process] Make Process::start non-blocking on Windows platform (romainneutron)

This PR was merged into the 2.3 branch.

Discussion
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[2.3][Process] Make Process::start non-blocking on Windows platform

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #9755
| License       | MIT

This PR is a proposition that solves issue #9755.

Let me sum-up what problems we have on Windows platform:
 - We can not use pipes with `proc_open` on Windows because `stream_set_blocking` does not work on this platform, resulting in blocking pipes and a blocking `Process::start` (see https://bugs.php.net/bug.php?id=51800, https://bugs.php.net/bug.php?id=47918 and https://bugs.php.net/bug.php?id=50856).
 - We can not use file handles for both `STDOUT` and `STDERR` as it might produce corrupted content (see https://bugs.php.net/bug.php?id=65650).
 - We currently use file handles for `STDOUT` and pipe for `STDERR` but it makes `Process::start` blocking.

The solution I propose here is to use native redirections, write `STDERR` / `STDOUT` in temporary files, read these files, finally cleanup.
It works pretty well, all tests pass on Windows. Better : [previous tests that were specific to this platform](https://github.com/symfony/symfony/blob/master/src/Symfony/Component/Process/Tests/AbstractProcessTest.php#L720-725) disappear as unix one are now okay :).

The drawback of this is the need of using `taskkill`: When stopping a process (`Process::stop` or in case of a timeout reached) `proc_terminate` does not kill the underlying process properly, only the `cmd` parent. The underlying process run by Process still runs after the `proc_terminate` call, having a lock on the temporary files we're using for getting the output, avoiding PHP to remove them (or any user on system) until the underlying process has finish to run).
So I use the `taskkill` Windows command to terminate the underlying process. This works well but I've to admit it's not pretty. If we do not use this hack, let's face that the underlying process is not stopped.

Last but not least, let's deal with the case we're running on Windows platform with PHP having --enable-sigchild environment (I don't know if it can really happen)
In this case:
 - we can not retrieve the `pid`
 - we can not `taskkill` the underlying process
 - it runs
 - locks remain on temporary files, we might not be able to remove them
We can't really deal with this.

Feedback more than welcome

Commits
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1f5bf32 [Process] Make Process::start non-blocking on Windows platform
fixed typo
[Process] Trow exceptions in case a Process method is supposed to be called after termination
bug #10480 [Process] Fixed fatal errors in getOutput and getErrorOutput when process was not started  (romainneutron)

This PR was merged into the 2.3 branch.

Discussion
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[Process] Fixed fatal errors in getOutput and getErrorOutput when process was not started

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #10022
| License       | MIT

This PR replaces #9452 and address the latest changes.
Side note : I've not updated `getExitCode`, `getExitCodeText` and `isSuccessful` as they were explicitly tested to return null in case the process is not started or terminated. I think it would be a BC break to do that.

Commits
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449fe01 [Process] Trow exceptions in case a Process method is supposed to be called after termination
0ae6858 [Process] fixed fatal errors in getOutput and getErrorOutput when process was not started
[Process] Fix unit tests in sigchild disabled environment
minor #10483 [2.3][Process] Fix unit tests in sigchild disabled environment (romainneutron)

This PR was merged into the 2.3 branch.

Discussion
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[2.3][Process] Fix unit tests in sigchild disabled environment

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| License       | MIT

We've been a bit fast when merging #10480 and tests were broken in the last update I did.

Commits
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5f6ee12 [Process] Fix unit tests in sigchild disabled environment
[Process] fix some typos and refactor some code
bug #10479 [2.3][Process] Fix escaping on Windows (romainneutron)

This PR was merged into the 2.3 branch.

Discussion
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[2.3][Process] Fix escaping on Windows

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| License       | MIT

Windows escaping is broken since the last merges.

After digging more on Windows escaping, I realised some things:
 - We forbid environment variable expansion by escaping `%APPDATA%` to `^%"APPDATA"^%`
 - We explicitly ask for variable expansion at runtime (running the command line with the [`/V:ON`](https://github.com/symfony/symfony/blob/2.3/src/Symfony/Component/Process/Process.php#L235) flag). Running a command containing `!APPDATA!` will be escaped and expanded (our previous rule is easily overriden)
 - On platform that are not windows, we use strong escaping that prevents any variable expansion (`$PATH` will be escaped to `'$PATH'` that is not interpreted as the current PATH)

We have three possibilities:
 - Keep this behavior as this.
 - Prefer a consistent API and use a strong escaping strategy everywhere, but it would result in a BC break (see #8975).
 - Allow environment variable expansion and escape `%APPDATA%` to `"%APPDATA%"`

Any thoughts about this ?

Commits
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0f65f90 [Process] Fix escaping on Windows
minor #10484 [Process] fix some typos and refactor some code (Tobion)

This PR was merged into the 2.3 branch.

Discussion
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[Process] fix some typos and refactor some code

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | -
| License       | MIT

Commits
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b422613 [Process] fix some typos and refactor some code
Added travis_retry to .travis.yml

As stated on their [blog](http://blog.travis-ci.com/2013-05-20-network-timeouts-build-retries/), this is the recommended way.

Example of a failed build because of it:
https://travis-ci.org/symfony/symfony/jobs/17664775
minor #10142 [Tests] Added travis_retry to .travis.yml (lavoiesl)

This PR was submitted for the 2.3-dev branch but it was merged into the 2.3 branch instead (closes #10142).

Discussion
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[Tests] Added travis_retry to .travis.yml

| Q             | A
| ------------- | ---
| Bug fix?      | -
| New feature?  | -
| BC breaks?    | -
| Deprecations? | -
| Tests pass?   | yes
| Fixed tickets | -
| License       | MIT
| Doc PR        | -

As stated on their [blog](http://blog.travis-ci.com/2013-05-20-network-timeouts-build-retries/), this is the recommended way.

Example of a failed build because of it:
https://travis-ci.org/symfony/symfony/jobs/17664775

Commits
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702432a Added travis_retry to .travis.yml
Fixed bug that incorrectly causes the "required" attribute to be omitted from select even though it contains the "multiple" attribute
bug #10491 Fixed bug that incorrectly causes the "required" attribute to be omitted from select even though it contains the "multiple" attribute (fabpot)

This PR was submitted for the 2.4 branch but it was merged into the 2.3 branch instead (closes #10491).

Discussion
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Fixed bug that incorrectly causes the "required" attribute to be omitted from select even though it contains the "multiple" attribute

According to the HTML5 specification the required attribute should be allowed in this case: "A select element with a required attribute and **without** a multiple attribute, and whose size is “1”, must have a child option element."

Related PR: https://github.com/symfony/symfony/pull/9030

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| License       | MIT

Commits
-------

f9aa676 Fixed bug that incorrectly causes the "required" attribute to be omitted from select even though it contains the "multiple" attribute
[Process] Remove unreachable code + avoid skipping tests in sigchild environment