x/tools/go/packages: provide alternative to deprecated LoadAllSyntax

[dominikh]

A fair number of tools will need the equivalent of the now deprecated LoadAllSyntax constant. Instead of forcing everyone to write their own bitwise OR of 9 constants, it would be nice if we could provide a constant for this. Unfortunately we can't call it NeedEverything, as LoadAllSyntax doesn't include NeedExportsFile, and including it unnecessarily probably causes unnecessary work by the compiler.

/cc @matloob

[matloob]

I'm actually a bit surprised by this. There are that many tools that need to be able to see (almost) all the fields on the package struct? My instinct is to avoid adding a NeedX field that has more than one bit set if we can avoid doing so

[dominikh]

It's possible that the tools I looked at used LoadAllSyntax out of convenience, not necessity.

However, intuitively, it seems to me that all tools that do full-fledged source based analysis will need the majority of fields in Package. They will need ASTs, they will need to resolve imports, and they will need type information. This amounts to LoadAllSyntax. Tools that need this amount of information include go/analysis runners, pre-go/analysis linters (golint, errcheck, ...) and, to a degree, code manipulation tools like goreturns, though these may not need NeedDeps, but then I'd argue that LoadAllSyntax ^ NeedDeps is easier than ORing 8 constants.

Am I missing something? Do most tools actually need much less information than I am thinking?

[matloob]

I think you're right that tools need this information. However I'd prefer to leave things as is unless we find a more pressing need for a LoadAllSyntax alternative. I think it's reasonable for tool authors to think through whether they need all the fields, and if they do, or-ing the 8 constants.

[dominikh]

I don't personally need this anymore, and I haven't seen anyone else ask for it. @matloob should we close this?

[matloob]

Yeah closing sounds good.