linters: avoid crash when analyzing function call

When encountering a statement such as:

	go functionName()

The identifier is not a local symbol but should be looked up in the
current package. Do not consider that all these statements will refer to
local variables.

The only way to do this is to run a second analyzer that depends on the
first one. Store all unresolved methods and functions into
a indirectCalls struct. Reuse that result in the second analyzer to
resolve the function declarations and check their bodies for the
defer log.PanicHandler() statement.

Fix one newly reported issues.

Signed-off-by: Robin Jarry <robin@jarry.cc>
Reviewed-by: Tim Culverhouse <tim@timculverhouse.com>

2 files changed, 52 insertions, 19 deletions

diff --git a/contrib/linters.go b/contrib/linters.go
index 7876cab6..41655a67 100644
--- a/contrib/linters.go
+++ b/contrib/linters.go
@@ -4,18 +4,36 @@ import (
 	"go/ast"
 	"go/token"
 	"go/types"
+	"reflect"
 
 	"golang.org/x/tools/go/analysis"
 )
 
+type indirectCalls struct {
+	methods   map[token.Pos]string
+	functions map[string]token.Pos
+}
+
 var PanicAnalyzer = &analysis.Analyzer{
-	Name: "panic",
-	Doc:  "finds goroutines that do not initialize the panic handler",
-	Run:  runPanic,
+	Name:       "panic",
+	Doc:        "finds goroutines that do not initialize the panic handler",
+	Run:        runPanic,
+	ResultType: reflect.TypeOf(&indirectCalls{}),
+}
+
+var PanicIndirectAnalyzer = &analysis.Analyzer{
+	Name:     "panicindirect",
+	Doc:      "finds functions called as goroutines that do not initialize the panic handler",
+	Run:      runPanicIndirect,
+	Requires: []*analysis.Analyzer{PanicAnalyzer},
 }
 
 func runPanic(pass *analysis.Pass) (interface{}, error) {
-	methods := make(map[token.Pos]string)
+	var calls indirectCalls
+
+	calls.methods = make(map[token.Pos]string)
+	calls.functions = make(map[string]token.Pos)
+
 	for _, file := range pass.Files {
 		ast.Inspect(file, func(n ast.Node) bool {
 			g, ok := n.(*ast.GoStmt)
@@ -38,11 +56,14 @@ func runPanic(pass *analysis.Pass) (interface{}, error) {
 				if ok {
 					f, ok := sel.Obj().(*types.Func)
 					if ok {
-						methods[f.Pos()] = f.Name()
+						calls.methods[f.Pos()] = f.Name()
 					}
 				}
 			case *ast.Ident:
 				block = inlineFuncBody(e)
+				if block == nil {
+					calls.functions[e.Name] = e.NamePos
+				}
 			}
 
 			if block == nil {
@@ -56,22 +77,28 @@ func runPanic(pass *analysis.Pass) (interface{}, error) {
 			return true
 		})
 	}
+
+	return &calls, nil
+}
+
+func runPanicIndirect(pass *analysis.Pass) (interface{}, error) {
+	calls := pass.ResultOf[PanicAnalyzer].(*indirectCalls)
+
 	for _, file := range pass.Files {
-		ast.Inspect(file, func(n ast.Node) bool {
-			f, ok := n.(*ast.FuncDecl)
-			if !ok {
-				return false
-			}
-			_, found := methods[f.Name.Pos()]
-			if !found {
-				return false
-			}
-			delete(methods, f.Name.Pos())
-			if !isPanicHandlerInstall(f.Body.List[0]) {
-				pass.Report(panicDiag(f.Body.Pos()))
+		for _, decl := range file.Decls {
+			if f, ok := decl.(*ast.FuncDecl); ok {
+				if _, ok := calls.methods[f.Name.Pos()]; ok {
+					delete(calls.methods, f.Name.Pos())
+				} else if _, ok := calls.functions[f.Name.Name]; ok {
+					delete(calls.functions, f.Name.Name)
+				} else {
+					continue
+				}
+				if !isPanicHandlerInstall(f.Body.List[0]) {
+					pass.Report(panicDiag(f.Body.Pos()))
+				}
 			}
-			return false
-		})
+		}
 	}
 
 	return nil, nil
@@ -86,6 +113,9 @@ func panicDiag(pos token.Pos) analysis.Diagnostic {
 }
 
 func inlineFuncBody(s *ast.Ident) *ast.BlockStmt {
+	if s.Obj == nil || s.Obj.Decl == nil {
+		return nil
+	}
 	d, ok := s.Obj.Decl.(*ast.AssignStmt)
 	if !ok {
 		return nil
@@ -121,6 +151,7 @@ type analyzerPlugin struct{}
 func (*analyzerPlugin) GetAnalyzers() []*analysis.Analyzer {
 	return []*analysis.Analyzer{
 		PanicAnalyzer,
+		PanicIndirectAnalyzer,
 	}
 }
 
diff --git a/worker/jmap/push.go b/worker/jmap/push.go
index 34a90ca4..2f7b05e6 100644
--- a/worker/jmap/push.go
+++ b/worker/jmap/push.go
@@ -16,6 +16,8 @@ import (
 )
 
 func (w *JMAPWorker) monitorChanges() {
+	defer log.PanicHandler()
+
 	events := push.EventSource{
 		Client:  w.client,
 		Handler: w.handleChange,