Tolerate missing ';' in message body (#218)

While still producing an error, see:
#200

Author: Alfus

ast/field.go

@@ -543,19 +543,21 @@ func NewMapFieldNode(mapType *MapTypeNode, name *IdentNode, equals *RuneNode, ta
 	if tag == nil {
 		panic("tag is nil")
 	}
-	if semicolon == nil {
-		panic("semicolon is nil")
-	}
-	numChildren := 5
+	numChildren := 4
 	if opts != nil {
 		numChildren++
 	}
+	if semicolon != nil {
+		numChildren++
+	}
 	children := make([]Node, 0, numChildren)
 	children = append(children, mapType, name, equals, tag)
 	if opts != nil {
 		children = append(children, opts)
 	}
-	children = append(children, semicolon)
+	if semicolon != nil {
+		children = append(children, semicolon)
+	}
 
 	return &MapFieldNode{
 		compositeNode: compositeNode{

ast/ranges.go

@@ -339,16 +339,17 @@ func NewReservedIdentifiersNode(keyword *KeywordNode, names []*IdentNode, commas
 	if keyword == nil {
 		panic("keyword is nil")
 	}
-	if semicolon == nil {
-		panic("semicolon is nil")
-	}
 	if len(names) == 0 {
 		panic("must have at least one name")
 	}
 	if len(commas) != len(names)-1 {
 		panic(fmt.Sprintf("%d names requires %d commas, not %d", len(names), len(names)-1, len(commas)))
 	}
-	children := make([]Node, 0, len(names)*2+1)
+	numChildren := len(names) * 2
+	if semicolon != nil {
+		numChildren++
+	}
+	children := make([]Node, 0, numChildren)
 	children = append(children, keyword)
 	for i, name := range names {
 		if i > 0 {
@@ -362,7 +363,9 @@ func NewReservedIdentifiersNode(keyword *KeywordNode, names []*IdentNode, commas
 		}
 		children = append(children, name)
 	}
-	children = append(children, semicolon)
+	if semicolon != nil {
+		children = append(children, semicolon)
+	}
 	return &ReservedNode{
 		compositeNode: compositeNode{
 			children: children,

parser/ast.go

@@ -135,6 +135,15 @@ func newEnumElements(semicolons []*ast.RuneNode, elements []ast.EnumElement) []a
 	return elems
 }
 
+func newMessageElements(semicolons []*ast.RuneNode, elements []ast.MessageElement) []ast.MessageElement {
+	elems := make([]ast.MessageElement, 0, len(semicolons)+len(elements))
+	for _, semicolon := range semicolons {
+		elems = append(elems, ast.NewEmptyDeclNode(semicolon))
+	}
+	elems = append(elems, elements...)
+	return elems
+}
+
 type nodeWithEmptyDecls[T ast.Node] struct {
 	Node       T
 	EmptyDecls []*ast.EmptyDeclNode
@@ -182,3 +191,12 @@ func toEnumElements[T ast.EnumElement](nodes nodeWithEmptyDecls[T]) []ast.EnumEl
 	}
 	return elements
 }
+
+func toMessageElements[T ast.MessageElement](nodes nodeWithEmptyDecls[T]) []ast.MessageElement {
+	elements := make([]ast.MessageElement, 1+len(nodes.EmptyDecls))
+	elements[0] = nodes.Node
+	for i, emptyDecl := range nodes.EmptyDecls {
+		elements[i+1] = emptyDecl
+	}
+	return elements
+}

parser/parser_test.go

@@ -266,6 +266,92 @@ func TestLenientParse_SemicolonLess(t *testing.T) {
 									int32 bar = 1 [foo = 1];
 								}`,
 		},
+		"message-field": {
+			Error: `syntax = "proto3";
+							message Foo {
+								int32 bar = 1
+							}`,
+			NoError: `syntax = "proto3";
+								message Foo {
+									;
+									int32 bar = 1;;
+								}`,
+		},
+		"message-field-cardinality": {
+			Error: `syntax = "proto3";
+							message Foo {
+								repeated int32 bar = 1
+							}`,
+			NoError: `syntax = "proto3";
+								message Foo {
+									repeated int32 bar = 1;
+								}`,
+		},
+		"message-field-options": {
+			Error: `syntax = "proto3";
+							message Foo {
+								int32 bar = 1 [foo = 1]
+							}`,
+			NoError: `syntax = "proto3";
+								message Foo {
+									int32 bar = 1 [foo = 1];
+								}`,
+		},
+		"message-reserved": {
+			Error: `syntax = "proto3";
+							message Foo {
+								reserved "FOO"
+							}`,
+			NoError: `syntax = "proto3";
+								message Foo {
+									;
+									reserved "FOO";;
+								}`,
+		},
+		"message-options": {
+			Error: `syntax = "proto3";
+							message Foo {
+								option (foo) = 1
+							}`,
+			NoError: `syntax = "proto3";
+								message Foo {
+									;
+									option (foo) = 1;;
+								}`,
+		},
+		"message-map-field": {
+			Error: `syntax = "proto3";
+							message Foo {
+								map<string, int32> bar = 1
+							}`,
+			NoError: `syntax = "proto3";
+								message Foo {
+									;
+									map<string, int32> bar = 1;;
+								}`,
+		},
+		"message-map-field-options": {
+			Error: `syntax = "proto3";
+							message Foo {
+								map<string, int32> bar = 1 [foo = 1]
+							}`,
+			NoError: `syntax = "proto3";
+								message Foo {
+									;
+									map<string, int32> bar = 1 [foo = 1];;
+								}`,
+		},
+		"message-option": {
+			Error: `syntax = "proto3";
+							message Foo {
+								option (foo) = 1
+							}`,
+			NoError: `syntax = "proto3";
+								message Foo {
+									;
+									option (foo) = 1;;
+								}`,
+		},
 	}
 	for name, input := range inputs {
 		name, input := name, input