From 807cc6ad2809cbede5c3c0a26617c5f5b8ecbf29 Mon Sep 17 00:00:00 2001
From: Lucas Bremgartner <lucas@bremis.ch>
Date: Wed, 12 Jan 2022 20:19:11 +0100
Subject: [PATCH] Fix false positives where errors are returned

Fixes: #5
---
 errchkjson.go              | 6 ++++++
 testdata/src/nosafe/a.go   | 9 +++++++++
 testdata/src/standard/a.go | 9 +++++++++
 3 files changed, 24 insertions(+)

diff --git a/errchkjson.go b/errchkjson.go
index 6c6dd77..4d6d45e 100644
--- a/errchkjson.go
+++ b/errchkjson.go
@@ -43,6 +43,12 @@ func (e *errchkjson) run(pass *analysis.Pass) (interface{}, error) {
 				return true
 			}
 
+			// if the error is returned, it is the caller's responsibility to check
+			// the return value.
+			if _, ok := n.(*ast.ReturnStmt); ok {
+				return false
+			}
+
 			ce, ok := n.(*ast.CallExpr)
 			if ok {
 				fn, _ := typeutil.Callee(pass.TypesInfo, ce).(*types.Func)
diff --git a/testdata/src/nosafe/a.go b/testdata/src/nosafe/a.go
index dd07e1b..e51d811 100644
--- a/testdata/src/nosafe/a.go
+++ b/testdata/src/nosafe/a.go
@@ -612,3 +612,12 @@ func NotJSONMarshal() {
 	f := func() bool { return false }
 	_ = f()
 }
+
+// Issue 5
+type T struct {
+	s string
+}
+
+func (t T) MarshalJSON() ([]byte, error) {
+	return json.Marshal(t.s) // not an error because it is the caller's responsibility to check the error
+}
diff --git a/testdata/src/standard/a.go b/testdata/src/standard/a.go
index 9fae0fd..a9e1a7b 100644
--- a/testdata/src/standard/a.go
+++ b/testdata/src/standard/a.go
@@ -612,3 +612,12 @@ func NotJSONMarshal() {
 	f := func() bool { return false }
 	_ = f()
 }
+
+// Issue 5
+type T struct {
+	f64 float64
+}
+
+func (t T) MarshalJSON() ([]byte, error) {
+	return json.Marshal(t.f64) // not an error because it is the caller's responsibility to check the error
+}