Make current dependencies optional

[qlquanle]

• The only true dependencies are Python (2.7.X), GSLab Python (4.1.0), PyYAML, and SCons.
• Create switches to implement our automated checks of other software and run example scripts.
  • Comment out lines in SConstruct or SConscript.
  • Add instructions on turning on dependencies in readme.

[yuchuan2016]

I think git-lfs is also a true dependency. Without git-lfs, we even cannot clone this repo.

Some other things:

• Shall we make lyx also a true dependency? I would vote for yes. We need at least one of lyx/tex to run paper_slides directory. We can say in README that users can turn off lyx and turn on tex, but the default one is lyx. (The default software for analysis directory is python)
• Shall we write check_matlab and check_latex in configuration_test.py now?
• Shall we write scanner for latex, similar to lyx now?

@stanfordquan @Shun-Yang , FYI if you have any opinion on above.

[Shun-Yang]

My suggestion is to make git-lfs and lyx as dependency, and postpone writing check_matlab, check_latex and latex_scanner to the end and see if we have time in this sprint to finish them. Of course, if you think they are relatively easy to do, then feel free to get this done now.

[qlquanle]

I vote making a note and delaying check_matlab and check_latex, same for latex_scanner.

I vote making TeX a dependency over LyX (smaller footprint, and a lot more people use TeX anecdotally). I think PIs may prefer LyX though.

[yuchuan2016]

Another potential problem is, if users simply write a Stata do file without turning on the stata dependency in config_global.yaml (say, if they uncomment the stata block in analysis/source/prepare_data/SConcsript, then configuration_test won't check stata requirements. Then the build may fail. This may violate the spirit that we want to catch all errors before users actually run the code.

[yuchuan2016]

@gentzkow , per team discussion, we have several options to specify software dependencies. We want your opinion over these options.

• Use the current structure. Specify dependencies in config_global.yaml. Check requirements only for softwares that have an entry Yes. The disadvantage is users may not be conscious enough to change it when using a new software.
• Add checks as a part of the builders when they are defined in SConstruct by Builder(action = gs.build_xx). Comment out lines that are not required. If a user want to use another builder, they need to uncomment the relevant line, and the builder will automatically do the check.
• Check the extensions of scripts in the repo that will be executed. Turn of the dependencies accordingly. This may involve a decent amount of work.

[gentzkow]

Thanks.

The second option sounds good to me if it can work robustly (i.e., if I uncomment a builder and the software isn't installed I'll always get a nice error; if I don't uncomment a builder but try to run steps that require that software I get an error as well (maybe a bit less nice))

[gentzkow]

(Otherwise, first option is fine)

[yuchuan2016]

Pull request created in #78.