Type and Pointer Analysis to-do list
====================================
Alan Donovan <adonovan@google.com>
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 pacakge 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.
