internal/lsp: create new cache for each analysis

Because diagnostics computations happen in parallel, we were getting
concurrent map writes by keeping one cache.

Change-Id: Ifa5adffe14c509168c9f8c5cb012f3fcd3a32441
Reviewed-on: https://go-review.googlesource.com/c/163161
Run-TryBot: Rebecca Stambler <[email protected]>
TryBot-Result: Gobot Gobot <[email protected]>
Reviewed-by: Michael Matloob <[email protected]>

Author: stamblerre

internal/lsp/cache/view.go

@@ -46,9 +46,7 @@ func (v *View) FileSet() *token.FileSet {
 }
 
 func (v *View) GetAnalysisCache() *source.AnalysisCache {
-	if v.analysisCache == nil {
-		v.analysisCache = source.NewAnalysisCache()
-	}
+	v.analysisCache = source.NewAnalysisCache()
 	return v.analysisCache
 }
 

internal/lsp/source/analysis.go

@@ -40,10 +40,6 @@ type analysisKey struct {
 func (c *AnalysisCache) analyze(pkgs []*packages.Package, analyzers []*analysis.Analyzer) []*action {
 	// TODO(matloob): Every time but the first, this needs to re-construct
 	// the invalidated parts of the action graph, probably under a lock?
-	// We'll take care of that later. For now, clear the entire cache!
-	for k := range c.m {
-		delete(c.m, k)
-	}
 
 	// Construct the action graph.
 	var mkAction func(a *analysis.Analyzer, pkg *packages.Package) *action