Type and Pointer Analysis to-do list

Alan Donovan [email protected]

Overall design

We should re-run the type and pointer analyses periodically, as we do with the indexer.

Version skew: how to mitigate the bad effects of stale URLs in old pages? We could record the file's length/CRC32/mtime in the go/loader, and refuse to decorate it with links unless they match at serving time.

Use the VFS mechanism when (a) enumerating packages and (b) loading them. (Requires planned changes to go/loader.)

Future work: shard this using map/reduce for larger corpora.

Testing: how does one test that a web page "looks right"?

Bugs

(*ssa.Program).Create requires transitively error-free packages. We can make this more robust by making the requirement transitively free of "hard" errors; soft errors are fine.

Markup of compiler errors is slightly buggy because they overlap with other selections (e.g. Idents). Fix.

User Interface

CALLGRAPH:

• Add a search box: given a search node, expand path from each entry point to it.
• Cause hovering over a given node to highlight that node, and all nodes that are logically identical to it.
• Initially expand the callgraph trees (but not their toggle divs).

CALLEES:

• The '(' links are not very discoverable. Highlight them?

Type info:

• In the source viewer's lower pane, use a toggle div around the IMPLEMENTS and METHODSETS lists, like we do in the package view. Only expand them initially if short.
• Include IMPLEMENTS and METHOD SETS information in search index.
• URLs in IMPLEMENTS/METHOD SETS always link to source, even from the package docs view. This makes sense for links to non-exported types, but links to exported types and funcs should probably go to other package docs.
• Suppress toggle divs for empty method sets.

Misc:

• The [X] button in the lower pane is subject to scrolling.
• Should the lower pane be floating? An iframe? When we change document.location by clicking on a link, it will go away. How do we prevent that (a la Gmail's chat windows)?
• Progress/status: for each file, display its analysis status, one of:
  • not in analysis scope
  • type analysis running...
  • type analysis complete (+ optionally: there were type errors in this file) And if PTA requested:
  • type analysis complete; PTA not attempted due to type errors
  • PTA running...
  • PTA complete
• Scroll the selection into view, e.g. the vertical center, or better still, under the pointer (assuming we have a mouse).

More features

Display the REFERRERS relation? (Useful but potentially large.)

Display the INSTANTIATIONS relation? i.e. given a type T, show the set of syntactic constructs that can instantiate it: var x T x := T{...} x = new(T) x = make([]T, n) etc + all INSTANTIATIONS of all S defined as struct{t T} or [n]T (Potentially a lot of information.) (Add this to guru too.)

Optimisations

Each call to addLink takes a (per-file) lock. The locking is fine-grained so server latency isn't terrible, but overall it makes the link computation quite slow. Batch update might be better.

Memory usage is now about 1.5GB for GOROOT + go.tools. It used to be 700MB.

Optimize for time and space. The main slowdown is the network I/O time caused by an increase in page size of about 3x: about 2x from HTML, and 0.7--2.1x from JSON (unindented vs indented). The JSON contains a lot of filenames (e.g. 820 copies of 16 distinct filenames). 20% of the HTML is L%d spans (now disabled). The HTML also contains lots of tooltips for long struct/interface types. De-dup or just abbreviate? The actual formatting is very fast.