Tab completion for Alias

[chewong]

---

Adding @williexu as a reviewer for the interactive portion.

do not merge this PR until azure-cli-2.0.31 is released.

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[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"

[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"

[derekbekoe]

@chewong Ready to review?

[chewong]

@derekbekoe, It's ready for review. I think alias source tests won't pass until azure cli 2.0.31 is released.

[derekbekoe]

What does telemetry have to do with building the collision table?
i.e. Why would a caller want to configure enable_telemetry.

[chewong]

This piece of code was accidentally checked in. Deleting it...

[derekbekoe]

You should use https://docs.python.org/3/library/unittest.mock.html#unittest.mock.patch for this kind of thing rather than just money-patching the value.
Otherwise it doesn't reset properly for each test and there'll be other issues later on.

[derekbekoe]

What's this file for?
Is loading a file during tab completion not slow?

[chewong]

The reason why I changed the tab completion approach is because of the limitation of the parser.

For example, if I have an alias pppp that points to create, and I perform:

az p<tab><tab>

There is no way to know whether we should inject pppp into external tab completion list because we don't know whether create is a first-level command (The parser will have policy,postgres, and provider as subparsers only, but not all the subparsers from the command table).

The alias_tab_completion file stores a json-encoded dictionary that is used during tab completion. Below is an example of the json object.

{
    "create": ["cosmosdb collection",
               "batch job", 
               "network dns record-set ptr", 
               "network vnet-gateway", 
               "sf cluster", 
               "network nsg rule", 
               "monitor autoscale profile".........]
}

Basically, it stores the alias command as the key and all the commands that can potentially go before that alias command as the value (i.e. parent command). That way, we can know when to autocomplete the alias by checking the current commands typed in the terminal.

For example:

az cosmosdb collection p<tab><tab>

check if 'cosmosdb collection' is a parent command of 'create' (alias command of 'pppp').
If so, add the alias to the external tab completion list.

I can take a look if there is any perf issue.

[troydai]

@derekbekoe ?

[derekbekoe]

He didn't want to merge this in before 2.0.31 is shipped.

[troydai]

That was close.

[troydai]

This can be rebase and then merge after CI passes.