Speedup GetSpellingSuggestion

[dzbarsky]

Noticed we weren't using buffers while trying the Kibana repro.

Before:

➜  kibana git:(main) ✗ time ../typescript-go/tsgo -p tsconfig.json -pprofDir /tmp/pprof                    
tsconfig.json:3:3 - error TS5090: Non-relative paths are not allowed. Did you forget a leading './'?

3   "compilerOptions": {
    ~~~~~~~~~~~~~~~~~
tsconfig.json:3:3 - error TS5102: Option 'baseUrl' has been removed. Please remove it from your configuration.
  Use '"paths": {"*": ["./*"]}' instead.

3   "compilerOptions": {
    ~~~~~~~~~~~~~~~~~

Found 2 errors in the same file, starting at: tsconfig.json:3

CPU profile: /tmp/pprof/92848-cpuprofile.pb.gz
Memory profile: /tmp/pprof/92848-memprofile.pb.gz
../typescript-go/tsgo -p tsconfig.json -pprofDir /tmp/pprof  273.49s user 45.88s system 299% cpu 1:46.77 total

After:

../typescript-go/tsgo -p tsconfig.json -pprofDir /tmp/pprof  237.25s user 40.39s system 286% cpu 1:36.83 total

[jakebailey]

This should only matter in erroring code. Are you silencing a whole bunch of errors?

[dzbarsky]

I'm not sure? The output above shows the only 2 errors that are reported.

[jakebailey]

If possible I'd print something out each time he function is called and count how often it is, or look around for ts-ignores/ts-expect-error.

I think we can totally accept an optimization like this, but we certainly aren't expecting the diagnostic code paths to be hot.

[dzbarsky]

There are around 3.1K ts-expect-error but I see GetSpellingSuggestion called around 750K times. I checked how many options were considered for each call (i.e. how many calls we executed to compute levenshtein distance, not just how many were provided):

count=751877 min=0 max=1060 avg=41.9747

A majority of calls only execute up to 2-3 computations, but for some reason there's 122K calls that consider exactly 175 possibilities...

Freq.   # of distances computed
325284 0
129899 1
122505 175
59133 2
26471 3
17585 26
14454 4
7951 211
7901 7
6482 47
5141 5
4515 87
4057 6
1774 375
1191 8
 935 538
 920 555
 890 9
 870 584
 832 514
 819 486
 807 431
 790 551
 790 522

[jakebailey]

That many ignored errors is terrifying; I would strongly suggest converting those to casts or similar.

But, would be good to improve nevertheless...

[RyanCavanaugh]

There are around 3.1K ts-expect-error

Can you characterize these for us? Why so many? We only compute spelling suggestions we can't find an identifier or property with that name -- situations that should be very, very uncommon in theory (and usually have straightforward type-side fixes available, e.g. declare missingVar: any).