Allow custom retainable temporary directories in CLIRunner.isolated_filesystem

[DasIch]

I would like to propose two changes to CLIRunner.isolated_filesystem, which I believe would significantly improve the experience of debugging tests using it:

1. Add an argument that allows users to specify the temporary directory.
2. Add an argument indicating that the temporary directory shouldn't be deleted (if an exception occurs).

The current behavior of isolated_filesystem of creating a random temporary directory without allowing specifying a specific directory or even a (partial) name and deleting it no matter what, makes it impossible to inspect the directory in case of test failures to gather more information. Even if the directory wouldn't be deleted, it's difficult to find.

By allowing the user to define a temporary directory, it's possible to take advantage of mechanisms such as py.test's tmpdir fixture or other systems to separate setup code from the actual test and to make the directory known to the user for inspection.

[untitaker]

Totally agree on 1, will merge a PR doing this. Not sure we need 2 as separate arg, we could assume user cleans up themselves if they pass their own directory.

Off topic, I'd like to see a click-contrib package that integrates Click's testing tools more tightly with pytest.

On 29 July 2015 00:16:57 CEST, "Daniel Neuhäuser" notifications@github.com wrote:

I would like to propose two changes to CLIRunner.isolated_filesystem,
which I believe would significantly improve the experience of debugging
tests using it:

1. Add an argument that allows users to specify the temporary
   directory.
2. Add an argument indicating that the temporary directory shouldn't be
   deleted (if an exception occurs).

The current behavior of isolated_filesystem of creating a random
temporary directory without allowing specifying a specific directory or
even a (partial) name and deleting it no matter what, makes it
impossible to inspect the directory in case of test failures to gather
more information. Even if the directory wouldn't be deleted, it's
difficult to find.

By allowing the user to define a temporary directory, it's possible to
take advantage of mechanisms such as py.test's tmpdir
fixture or other systems to
separate setup code from the actual test and to make the directory
known to the user for inspection.

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