Simpler CLI targets

[ahopkins]

This simplifies the CLI experience, but should continue to work as it currently does.

Currently, to serve a directory:

sanic /some/path --simple

And, a factory:

sanic path.to.server:create_app --factory

Without the --simple or --factory flags it would fail. This PR will look at the targets passed. If it is a directory, then launch simple server. If it is a function, try calling it.

These are now all possible:

sanic path.to.server:app

sanic /some/path

sanic path.to.server:create_app

The main motivation behind this is the ongoing discussion to encourage the CLI usage more and more.

[Tronic]

I have a feeling that this is too ambiguous. Many things could be either module or path, e.g.

c:\directory   # unless it checks that after colon only certain characters are used
module.app  # unless it checks that module.app is not a file or directory

Maybe with stronger heuristics for the corner cases, combined with Path(...).exists(). For improving usability, it might also be useful to check by default for app in the module without having to specify that, i.e. sanic mymodule to run mymodule:app.

[ahopkins]

Yes, it already does these things.

For improving usability, it might also be useful to check by default for app in the module without having to specify that, i.e. sanic mymodule to run mymodule:app.

This would assume people use app. I'm not opposed. I have added this change.

[ahopkins]

FTR, passing a file will not work. Only a directory.

[ahopkins]

@Tronic

1. The implied paths should only be used to serve a directory (i) if it is an existing directory, and (ii) has at least one path seperator in it. This should help to differentiate between a directory that happens to be named as a module. Also, no : splitting if the input startswith C:\. This should help clear up some ambiguity.
2. sanic somemodule will look for app that is a Sanic instance as per your suggestion.

[codecov]

Codecov Report

Patch coverage: 57.142% and project coverage change: -0.240 ⚠️

Comparison is base (1a63b9b) 88.912% compared to head (7de036c) 88.673%.

❗ Current head 7de036c differs from pull request most recent head e479cc1. Consider uploading reports for the commit e479cc1 to get more accurate results

Additional details and impacted files

@@              Coverage Diff              @@
##              main     #2700       +/-   ##
=============================================
- Coverage   88.912%   88.673%   -0.240%     
=============================================
  Files           92        87        -5     
  Lines         7017      6860      -157     
  Branches      1196      1180       -16     
=============================================
- Hits          6239      6083      -156     
- Misses         533       536        +3     
+ Partials       245       241        -4     

Impacted Files	Coverage Δ
sanic/worker/loader.py	84.705% <57.142%> (-9.961%)	⬇️

... and 13 files with indirect coverage changes

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[Tronic]

Doing a full review later. The logic is quite complicated and needs some more thought to see that it handles all use cases correctly.