internal/lsp/source: offer the fast fuzzy matcher as an option

Hook up the new fast SymbolMatcher as an option.

Benchmark ("test" in x/tools): 48ms->21ms (with the new matcher)
Benchmark ("test" in kubernetes): 857ms->199ms (with the new matcher)

Change-Id: Ic638eda1ed10572638f32879dd9b56467ae305ef
Reviewed-on: https://go-review.googlesource.com/c/tools/+/338695
Trust: Robert Findley <rfindley@google.com>
Run-TryBot: Robert Findley <rfindley@google.com>
gopls-CI: kokoro <noreply+kokoro@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Rebecca Stambler <rstambler@golang.org>

gopls/doc/settings.md

@@ -397,6 +397,7 @@ Must be one of:
 
 * `"CaseInsensitive"`
 * `"CaseSensitive"`
+* `"FastFuzzy"`
 * `"Fuzzy"`
 Default: `"Fuzzy"`.
 

internal/lsp/source/api_json.go

@@ -325,6 +325,10 @@ var GeneratedAPIJSON = &APIJSON{
 						Value: "\"CaseSensitive\"",
 						Doc:   "",
 					},
+					{
+						Value: "\"FastFuzzy\"",
+						Doc:   "",
+					},
 					{
 						Value: "\"Fuzzy\"",
 						Doc:   "",

internal/lsp/source/options.go

@@ -543,6 +543,7 @@ type SymbolMatcher string
 
 const (
 	SymbolFuzzy           SymbolMatcher = "Fuzzy"
+	SymbolFastFuzzy       SymbolMatcher = "FastFuzzy"
 	SymbolCaseInsensitive SymbolMatcher = "CaseInsensitive"
 	SymbolCaseSensitive   SymbolMatcher = "CaseSensitive"
 )
@@ -834,6 +835,7 @@ func (o *Options) set(name string, value interface{}, seen map[string]struct{})
 	case "symbolMatcher":
 		if s, ok := result.asOneOf(
 			string(SymbolFuzzy),
+			string(SymbolFastFuzzy),
 			string(SymbolCaseInsensitive),
 			string(SymbolCaseSensitive),
 		); ok {

internal/lsp/source/workspace_symbol.go

@@ -157,6 +157,8 @@ func newSymbolCollector(matcher SymbolMatcher, style SymbolStyle, query string)
 	switch matcher {
 	case SymbolFuzzy:
 		m = parseQuery(query)
+	case SymbolFastFuzzy:
+		m = fuzzy.NewSymbolMatcher(query).Match
 	case SymbolCaseSensitive:
 		m = matchExact(query)
 	case SymbolCaseInsensitive: