From 854e4f15535536d0b11d0b53f1781fe7f4ccbdf3 Mon Sep 17 00:00:00 2001
From: "Dmitry A. Shashkin" <d.a.shashkin@gmail.com>
Date: Wed, 28 Feb 2024 08:04:44 +1100
Subject: [PATCH] feat: check structs within arrays/slices/maps (#80)

---
 musttag.go                  | 21 ++++++++------
 testdata/src/tests/tests.go | 56 +++++++++++++++++++++++++++++++++++++
 2 files changed, 68 insertions(+), 9 deletions(-)

diff --git a/musttag.go b/musttag.go
index b7e41f3..d791177 100644
--- a/musttag.go
+++ b/musttag.go
@@ -150,16 +150,19 @@ type checker struct {
 }
 
 func (c *checker) parseStruct(typ types.Type) (*types.Struct, bool) {
-	for {
-		// unwrap pointers (if any) first.
-		ptr, ok := typ.(*types.Pointer)
-		if !ok {
-			break
-		}
-		typ = ptr.Elem()
-	}
-
 	switch typ := typ.(type) {
+	case *types.Pointer:
+		return c.parseStruct(typ.Elem())
+
+	case *types.Array:
+		return c.parseStruct(typ.Elem())
+
+	case *types.Slice:
+		return c.parseStruct(typ.Elem())
+
+	case *types.Map:
+		return c.parseStruct(typ.Elem())
+
 	case *types.Named: // a struct of the named type.
 		pkg := typ.Obj().Pkg()
 		if pkg == nil {
diff --git a/testdata/src/tests/tests.go b/testdata/src/tests/tests.go
index 9112dab..bd869be 100644
--- a/testdata/src/tests/tests.go
+++ b/testdata/src/tests/tests.go
@@ -51,6 +51,62 @@ func embeddedType() {
 	json.Marshal(&Foo{}) // want "the given struct should be annotated with the `json` tag"
 }
 
+func nestedArrayType() {
+	type Bar struct {
+		NoTag string
+	}
+	type Foo struct {
+		Bars [5]Bar `json:"bars"`
+	}
+	var foo Foo
+	json.Marshal(foo)    // want "the given struct should be annotated with the `json` tag"
+	json.Marshal(&foo)   // want "the given struct should be annotated with the `json` tag"
+	json.Marshal(Foo{})  // want "the given struct should be annotated with the `json` tag"
+	json.Marshal(&Foo{}) // want "the given struct should be annotated with the `json` tag"
+}
+
+func nestedSliceType() {
+	type Bar struct {
+		NoTag string
+	}
+	type Foo struct {
+		Bars []Bar `json:"bars"`
+	}
+	var foo Foo
+	json.Marshal(foo)    // want "the given struct should be annotated with the `json` tag"
+	json.Marshal(&foo)   // want "the given struct should be annotated with the `json` tag"
+	json.Marshal(Foo{})  // want "the given struct should be annotated with the `json` tag"
+	json.Marshal(&Foo{}) // want "the given struct should be annotated with the `json` tag"
+}
+
+func nestedMapType() {
+	type Bar struct {
+		NoTag string
+	}
+	type Foo struct {
+		Bars map[string]Bar `json:"bars"`
+	}
+	var foo Foo
+	json.Marshal(foo)    // want "the given struct should be annotated with the `json` tag"
+	json.Marshal(&foo)   // want "the given struct should be annotated with the `json` tag"
+	json.Marshal(Foo{})  // want "the given struct should be annotated with the `json` tag"
+	json.Marshal(&Foo{}) // want "the given struct should be annotated with the `json` tag"
+}
+
+func nestedComplexType() {
+	type Bar struct {
+		NoTag string
+	}
+	type Foo struct {
+		Bars **[][]map[string][][5][5]map[string]*Bar `json:"bars"`
+	}
+	var foo Foo
+	json.Marshal(foo)    // want "the given struct should be annotated with the `json` tag"
+	json.Marshal(&foo)   // want "the given struct should be annotated with the `json` tag"
+	json.Marshal(Foo{})  // want "the given struct should be annotated with the `json` tag"
+	json.Marshal(&Foo{}) // want "the given struct should be annotated with the `json` tag"
+}
+
 func recursiveType() {
 	// should not cause panic; see issue #16.
 	type Foo struct {