Do not reopen Project explorer on startup

[homocomputeris]

Description

What steps will reproduce the problem?

1. Close Project explorer pane
2. Close Spyder
3. Open Spyder

What is the expected output?
No Project explorer

What do you see instead?
Project explorer is back, however the corresponding checkbox in Projects drop-down menu is unchecked

Please provide any additional information below
I don't know if it's a bug or a feature. Anyway, Spyder should not decide for me what to see. Exists since 3.2.4 at least.

Version and main components

• Spyder Version: 3.2.6
• Python Version: 3.6.4
• Qt Versions: 5.10.0, PyQt5 5.9.2 on Linux

Dependencies

pyflakes >=0.6.0 :  1.6.0 (OK)
pycodestyle >=2.3:  2.3.1 (OK)
pygments >=2.0   :  2.2.0 (OK)
pandas >=0.13.1  :  0.21.0 (OK)
numpy >=1.7      :  1.14.0 (OK)
sphinx >=0.6.6   :  1.6.6 (OK)
rope >=0.9.4     :  0.10.6 (OK)
jedi >=0.9.0     :  0.11.1 (OK)
psutil >=0.3     :  5.4.3 (OK)
nbconvert >=4.0  :  5.3.1 (OK)
sympy >=0.7.3    :  1.1.1 (OK)
cython >=0.21    :  0.27.3 (OK)
qtconsole >=4.2.0:  4.3.1 (OK)
IPython >=4.0    :  6.2.1 (OK)
pylint >=0.25    :  1.8.1 (OK)

[csabella]

@homocomputeris Thanks for the report!

[CAM-Gerlach]

Thanks @csabella , I've seen this one consistently as well (on Windows) but I didn't want to gum up the works reporting it if it only bothered me...looks like that's not the case. Not sure its truly a bug but rather a side effect of consistent behavior (project explorer always opening on opening a project) that we may want to reconsider, though it has certainly bug ged me, heh.

I guess the broader question is when opening a project (which is the routine underlying this), would we then not want to open project explorer if it isn't already open in the previous project? What if no project was open previously? Just save the last known state and go by that?

Just some questions to ponder...

[jitseniesen]

It bothered me as well, to be honest. Can we do the same as we do for the Outline panel? I don't know exactly when the Outline panel appears and disappears, but it does not bother me so the rules for the Outline panel are at least sensible for how I use it.

[CAM-Gerlach]

@jitseniesen

Can we do the same as we do for the Outline panel?

At least on Windows, I haven't observed any funny business with that in any Spyder version I've used (since 3.2.1).

[jitseniesen]

I think doing the same as we do for the Outline panel means that we do not automatically close the Project Explorer panel when a project is closed; instead we leave the Project Explorer panel empty. Conversely, if a project is opened, the Project Explorer is not automatically opened.

On reflection, I think @CAM-Gerlach 's idea in #6292 (comment) is better: when closing a project, remember if the Project Explorer was open. When opening a project, only open the Project Explorer if it was open the last time that a project was closed.

[jitseniesen]

Sorry, I closed the issue by accident