Support dev servers defined in a mojoconfig file.

Support dev servers defined in a mojoconfig file.

This patch allows one to define local servers to be set up by devtools
(`mojo_run` / `mojo_test`) in a config file. Each server is described as a
dictionary defining the host and the mappings:

    {
      'host': 'https://core.mojoapps.io/',
      'mappings': [
        ('packages/', ['@{BUILD_DIR}/gen/dart-pkg/packages']),
        ('', ['@{BUILD_DIR}']),
      ],
    },

This allows us to support running 'exploded' dart apps, see
https://github.com/domokit/devtools/issues/30 .

This patch also adds an example config file for the setup we will want to use
in the Mojo repo. As of this CL one has to explicitly pass --config-file
mojoconfig to make use of the config file. We will probably want to make
devtools discover this file automatically.

R=qsr@chromium.org

Committed: https://chromium.googlesource.com/external/mojo/+/7b674fecee63ca43a90d32a3405eea5e2707883e

[ppi, 2015-08-03 16:08:30]

Hi Ben,

ptal.

cc: John

[qsr, 2015-08-04 14:06:45]

https://codereview.chromium.org/1259793008/diff/1/mojo/devtools/common/devtoo...
File mojo/devtools/common/devtoolslib/shell_config.py (right):

https://codereview.chromium.org/1259793008/diff/1/mojo/devtools/common/devtoo...
mojo/devtools/common/devtoolslib/shell_config.py:118: return
collections.defaultdict(lambda: None, config_dict)
I do not think you need a defaultdict here.

https://codereview.chromium.org/1259793008/diff/1/mojoconfig
File mojoconfig (right):

https://codereview.chromium.org/1259793008/diff/1/mojoconfig#newcode16
mojoconfig:16: ('packages/', '@{BUILD_DIR}/gen/dart-pkg/packages'),
As discussed, please use a dictionary for the target paths already as you know
you will want this in a near future.

Also document that the ordering matters.

[ppi, 2015-08-04 16:04:51]

https://codereview.chromium.org/1259793008/diff/1/mojo/devtools/common/devtoo...
File mojo/devtools/common/devtoolslib/shell_config.py (right):

https://codereview.chromium.org/1259793008/diff/1/mojo/devtools/common/devtoo...
mojo/devtools/common/devtoolslib/shell_config.py:118: return
collections.defaultdict(lambda: None, config_dict)
On 2015/08/04 14:06:45, qsr wrote:
> I do not think you need a defaultdict here.

Done.

https://codereview.chromium.org/1259793008/diff/1/mojoconfig
File mojoconfig (right):

https://codereview.chromium.org/1259793008/diff/1/mojoconfig#newcode16
mojoconfig:16: ('packages/', '@{BUILD_DIR}/gen/dart-pkg/packages'),
On 2015/08/04 14:06:45, qsr wrote:
> As discussed, please use a dictionary for the target paths already as you know
> you will want this in a near future.
> 
> Also document that the ordering matters.

Done (using a list of paths, not a dictionary, as clarified offline).

[qsr, 2015-08-05 08:06:44]

Documentation for the config file is wrong in the cl documentation.

[qsr, 2015-08-05 08:11:14]

LGTM with nits.

https://codereview.chromium.org/1259793008/diff/40001/mojo/devtools/common/de...
File mojo/devtools/common/devtoolslib/shell_arguments.py (right):

https://codereview.chromium.org/1259793008/diff/40001/mojo/devtools/common/de...
mojo/devtools/common/devtoolslib/shell_arguments.py:186: return shell_args
Why do you both update the reference you are given and returns it? This is kind
of strange.

https://codereview.chromium.org/1259793008/diff/40001/mojo/devtools/common/de...
File mojo/devtools/common/devtoolslib/shell_config.py (right):

https://codereview.chromium.org/1259793008/diff/40001/mojo/devtools/common/de...
mojo/devtools/common/devtoolslib/shell_config.py:154: mojoconfig = None
You can probably move the definition of this variable after the if.

[ppi, 2015-08-05 10:54:01]

Thanks!

Fixed the commit description.

https://codereview.chromium.org/1259793008/diff/40001/mojo/devtools/common/de...
File mojo/devtools/common/devtoolslib/shell_arguments.py (right):

https://codereview.chromium.org/1259793008/diff/40001/mojo/devtools/common/de...
mojo/devtools/common/devtoolslib/shell_arguments.py:186: return shell_args
On 2015/08/05 08:11:13, qsr wrote:
> Why do you both update the reference you are given and returns it? This is
kind
> of strange.

This matches what all other functions do. I'm happy to fix them (probably going
for modifying the passed list and not returning anything), but would prefer not
to make this change in this cl.

https://codereview.chromium.org/1259793008/diff/40001/mojo/devtools/common/de...
File mojo/devtools/common/devtoolslib/shell_config.py (right):

https://codereview.chromium.org/1259793008/diff/40001/mojo/devtools/common/de...
mojo/devtools/common/devtoolslib/shell_config.py:154: mojoconfig = None
On 2015/08/05 08:11:13, qsr wrote:
> You can probably move the definition of this variable after the if.

Done.

[ppi, 2015-08-05 10:57:18]

Committed patchset #4 (id:60001) manually as
7b674fecee63ca43a90d32a3405eea5e2707883e (presubmit successful).