BUG: Windows write path with AD file writer plugins

[prjemian]

A problem occurred when staging an area detector HDF file writing plugin and the IOC is running on Windows.

One feature of any of the AD file writers is the ability to control the directory where the file will be written. When the file_path attribute is written, the EPICS IOC will append a / directory separator to the given file path if it does not have one already. The choice of / even happens for Windows IOCs!

The problem in ophyd is two-fold:

1. these are the lines that strip any supplied directory separator if it is the last item in the given file path: https://github.com/bluesky/ophyd/blob/1b9e91be7483d94636ae0bfa14bf13702e07b969/ophyd/areadetector/filestore_mixins.py#L417-L418
2. the ophyd .set() to this signal waits at this line (with no timeout): https://github.com/bluesky/ophyd/blob/1b9e91be7483d94636ae0bfa14bf13702e07b969/ophyd/areadetector/filestore_mixins.py#L432 since the return value will be different than the expected.

Here is the code that fixes the problem for one detector, by making a custom HDF5 Plugin for a Windows IOC (the other support code is added):

class MyHDF5Plugin(FileStoreHDF5IterativeWrite, HDF5Plugin_V34):

    def make_filename(self):
        """Override from ophyd.areadetector.filestore_mixins.FileStorePluginBase"""
        filename = new_short_uid()
        formatter = datetime.datetime.now().strftime
        write_path = formatter(self.write_path_template) + "\\"  # the FIX!
        read_path = formatter(self.read_path_template)
        return filename, read_path, write_path

class MyProcessPlugin(ProcessPlugin):

    pool_max_buffers = None

class MyDexelaDetector(SingleTrigger, DexelaDetector):
    """Dexela detector(s) as used by 9-ID-C USAXS."""

    hdf1 = ADComponent(
        MyHDF5Plugin,
        "HDF1:",
        write_path_template="W:\\USAXS_data\\test\\dexela\\%Y\\%m\\%d\\",
        read_path_template="/share1/USAXS_data/test/dexela/%Y/%m/%d/",
        path_semantics="windows",
    )
    image = ADComponent(ImagePlugin, "image1:")
    proc1 = ADComponent(MyProcessPlugin, "Proc1:")

dexela_det = MyDexelaDetector("9idcDEX:", name="dexela_det")

[mrakitin]

MyProcessPlugin can be replaced by https://github.com/bluesky/ophyd/blob/03585f0b02752d5975da393a889e5c5cecd06fd7/ophyd/areadetector/plugins.py#L1504-L1507

That removes pool_max_buffers via https://github.com/bluesky/ophyd/blob/03585f0b02752d5975da393a889e5c5cecd06fd7/ophyd/areadetector/plugins.py#L1025-L1028

[klauer]

EpicsPathSignal may need some updating to fix this? https://github.com/bluesky/ophyd/blob/03585f0b02752d5975da393a889e5c5cecd06fd7/ophyd/areadetector/paths.py#L87

[prjemian]

On slack.com, it was suggested that #749 might address this directly with a resolution.