Fix handling of ProjectName.deps.json file in incremental builds

[dsplaisted]

Fixes #408

The issue was that if the ProjectName.deps.json file was up to date, then the GenerateDepsFile target would be skipped and the deps.json file would not be included in the FileWrites item group, causing it to get deleted by IncrementalClean. This change adds a separate target which always runs which adds the deps.json file to the FileWrites group even if GenerateDepsFile isn't run.

[dsplaisted]

@nguerrera @srivatsn for review

@AndyGerlicher @rainersigwald, Does this look like the right way to correctly handle IncrementalClean?

[rainersigwald]

Don't put this in a separate target, add it to GenerateBuildDependencyFile.

MSBuild will manipulate items that it can statically understand even when it skips a target for being up to date. It wasn't doing that before because it can't predict what the task would have output.

[dsplaisted]

@rainersigwald Thanks for clarifying, I've updated the PR accordingly.

[srivatsn]

@dsplaisted can you fill out the escrow template and tag Matt.

[nguerrera]

I feel like I've seen this output-to-file-writes pattern all over the place (or was it really just here or just impactful here?). Do we need to scrub?

[dsplaisted]

@nguerrera

I feel like I've seen this output-to-file-writes pattern all over the place (or was it really just here or just impactful here?). Do we need to scrub?

I originally added to the FileWrites item to fix #305, where cleaning a project would leave some files in the output folder. Along with that, I added a The_clean_target_removes_all_files_from_the_output_folder test, which I think should catch anything that is missing from FileWrites.

[dsplaisted]

@MattGertz for approval

Scenario

Incremental build (building twice in a row) shouldn't delete files from output directory.

Bug

#408

Workarounds

Rebuild instead of build. The unit testing team is saying this blocks their scenarios too.

Risk

Low - Tests should cover any impacted scenarios

Performance Impact

Low - the change is only writing 3 additional lines to a file that is already written during build, and deleting 3 files during clean

Regression Analysis

This was a regression introduced in #381