Alias 0.3.0

[chewong]

---

Alias command spec: https://github.com/chewong/azure-cli-alias-extension/blob/dev/doc/az-alias-command-spec.md

This checklist is used to make sure that common guidelines for a pull request are followed.

General Guidelines

• Have you run ./scripts/ci/test_static.sh locally? (pip install pylint flake8 required)
• Have you run python scripts/ci/test_index.py -q locally?

[azuresdkci]

If this PR is for a new extension or change to an existing extension, use the following to try out the changes in this PR:

docker run -it microsoft/azure-cli:latest
export EXT=<NAME>
pip install --upgrade --target ~/.azure/cliextensions/$EXT "git+https://github.com/chewong/[email protected]#subdirectory=src/$EXT&egg=$EXT"

[troydai]

I don't think we need this. You can break the line to fix in 120 char.

[troydai]

Could you elaborate this?

[chewong]

I don't have access to load_cmd_tbl_func in custom.py (need the entire command table for alias and command validation when the user invokes alias create). This is a mechanism to save/cache the entire command table globally so custom.py can have access to it.

[derekbekoe]

It'd be good to add this comment as an actual comment in the code. No-one is going to come back and look at this comment in this PR to try and understand it.

[troydai]

Is there a way to avoid global?

[chewong]

Added a class called AliasCache to store the reserved commands.

[troydai]

Could you elaborate the logic here in the comments?

[chewong]

The logic here is to not transform named arguments. For example, if you have an alias ls pointing to list, running az vm create -g xxx -n ls should not yield az vm create -g xxx -n list,
I think I can make it less ugly and more readable.

[troydai]

@chewong feel free to merge when @derekbekoe ack this.

[derekbekoe]

You need to remove the completer for --name on the 'az alias create' command other I'll get completions for aliases that already exist which is exactly what I wouldn't want.

[derekbekoe]

What's the point in a class that has only one method, no constructor and even that method is static?

[derekbekoe]

AliasCache.reserved_commands could just be a variable like alias_cache_reserved_commands and cache_reserved_commands could be a regular method?

[derekbekoe]

It'd be good to add this comment as an actual comment in the code. No-one is going to come back and look at this comment in this PR to try and understand it.

[derekbekoe]

Why this name change?

[chewong]

Changed it to AliasExtCommandLoader.

[derekbekoe]

This code is similar to that in alias_event_handler.
Should have a util method to update azext_alias.AliasCache.reserved_commands so you don't have to duplicate this.

[derekbekoe]

Consider a util method called is_alias_create_command(args) since I've seen this used in a few places. I believe that's what args[:2] == ['alias', 'create'] is for?

[derekbekoe]

Pass in a string to CLIError()

Currently, the user will see this for a bad alias file.

# az alias list
alias: Error parsing the configuration file - File contains no alias headers.file: '/root/.azure/alias', line: 1'rg]'. Please fix the problem manually.
Traceback (most recent call last):
  File "/root/.azure/cliextensions/alias/azext_alias/custom.py", line 91, in _get_alias_table
    alias_table.read(GLOBAL_ALIAS_PATH)
  File "/usr/local/lib/python3.6/configparser.py", line 697, in read
    self._read(fp, filename)
  File "/usr/local/lib/python3.6/configparser.py", line 1080, in _read
    raise MissingSectionHeaderError(fpname, lineno, line)
configparser.MissingSectionHeaderError: File contains no section headers.
file: '/root/.azure/alias', line: 1
'rg]\n'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/local/lib/python3.6/site-packages/knack/cli.py", line 197, in invoke
    cmd_result = self.invocation.execute(args)
  File "/usr/local/lib/python3.6/site-packages/azure/cli/core/commands/__init__.py", line 347, in execute
    six.reraise(*sys.exc_info())
  File "/usr/local/lib/python3.6/site-packages/six.py", line 693, in reraise
    raise value
  File "/usr/local/lib/python3.6/site-packages/azure/cli/core/commands/__init__.py", line 319, in execute
    result = cmd(params)
  File "/usr/local/lib/python3.6/site-packages/azure/cli/core/commands/__init__.py", line 180, in __call__
    return super(AzCliCommand, self).__call__(*args, **kwargs)
  File "/usr/local/lib/python3.6/site-packages/knack/commands.py", line 109, in __call__
    return self.handler(*args, **kwargs)
  File "/usr/local/lib/python3.6/site-packages/azure/cli/core/__init__.py", line 420, in default_command_handler
    result = op(**command_args)
  File "/root/.azure/cliextensions/alias/azext_alias/custom.py", line 58, in list_alias
    alias_table = _get_alias_table()
  File "/root/.azure/cliextensions/alias/azext_alias/custom.py", line 96, in _get_alias_table
    raise CLIError()
knack.util.CLIError

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/local/lib/python3.6/runpy.py", line 193, in _run_module_as_main
    "__main__", mod_spec)
  File "/usr/local/lib/python3.6/runpy.py", line 85, in _run_code
    exec(code, run_globals)
  File "/usr/local/lib/python3.6/site-packages/azure/cli/__main__.py", line 39, in <module>
    exit_code = cli_main(az_cli, sys.argv[1:])
  File "/usr/local/lib/python3.6/site-packages/azure/cli/__main__.py", line 29, in cli_main
    return cli.invoke(args)
  File "/usr/local/lib/python3.6/site-packages/knack/cli.py", line 207, in invoke
    exit_code = self.exception_handler(ex)
  File "/usr/local/lib/python3.6/site-packages/azure/cli/core/__init__.py", line 85, in exception_handler
    return handle_exception(ex)
  File "/usr/local/lib/python3.6/site-packages/azure/cli/core/util.py", line 26, in handle_exception
    logger.error(ex.args[0])
IndexError: tuple index out of range

As a quick test, I replaced the empty string with 'Unable to get aliases' and now I see this which is much better:

# az alias list
alias: Error parsing the configuration file - File contains no alias headers.file: '/root/.azure/alias', line: 1'rg]'. Please fix the problem manually.
Unable to get aliases

[chewong]

Replaced this with return get_config_parser() so az alias list and other actions that depends on get_alias_table() will just get an empty alias table.

[derekbekoe]

This validation should happen in a _validators.py file.
See others in the CLI for examples.

[derekbekoe]

Please modify the description in setup.py to conform to https://github.com/Azure/azure-cli-extensions/blob/master/docs/extension_summary_guidelines.md.
Something like "Support for command aliases." would be okay.