Fix generators to check empty field set slice

pkg/generators/golang/builders_generator.go

@@ -240,26 +240,35 @@ func (g *BuildersGenerator) generateStructBuilderSource(typ *concepts.Type) {
 		// {{ $builderCtor }} creates a new builder of '{{ .Type.Name }}' objects.
 		func {{ $builderCtor }}() *{{ $builderName }} {
 			return &{{ $builderName }}{
-				fieldSet_: make([]bool, {{ fieldSetSize .Type }}),
+				fieldSet_: make([]bool, {{ fieldSetSize $.Type }}),
 			}
 		}
 
 		{{ if .Type.IsClass }}
 			// Link sets the flag that indicates if this is a link.
 			func (b *{{ $builderName }}) Link(value bool) *{{ $builderName }} {
+				if len(b.fieldSet_) == 0 {
+					b.fieldSet_ = make([]bool, {{ fieldSetSize $.Type }})
+				}
 				b.fieldSet_[0] = true
 				return b
 			}
 
 			// ID sets the identifier of the object.
 			func (b *{{ $builderName }}) ID(value string) *{{ $builderName }} {
+				if len(b.fieldSet_) == 0 {
+					b.fieldSet_ = make([]bool, {{ fieldSetSize $.Type }})
+				}
 				b.id = value
 				b.fieldSet_[1] = true
 				return b
 			}
 
 			// HREF sets the link to the object.
 			func (b *{{ $builderName }}) HREF(value string) *{{ $builderName }} {
+				if len(b.fieldSet_) == 0 {
+					b.fieldSet_ = make([]bool, {{ fieldSetSize $.Type }})
+				}
 				b.href = value
 				b.fieldSet_[2] = true
 				return b
@@ -302,6 +311,9 @@ func (g *BuildersGenerator) generateStructBuilderSource(typ *concepts.Type) {
 				{{ lineComment .Type.Doc }}
 				{{ if .Link }}
 					func (b *{{ $builderName }}) {{ $setterName }}(value {{ $setterType }}) *{{ $builderName }} {
+						if len(b.fieldSet_) == 0 {
+							b.fieldSet_ = make([]bool, {{ fieldSetSize $.Type }})
+						}
 						b.{{ $fieldName }} = value
 						b.fieldSet_[{{ $fieldIndex }}] = true
 						return b
@@ -310,6 +322,9 @@ func (g *BuildersGenerator) generateStructBuilderSource(typ *concepts.Type) {
 					{{ $elementType := valueType .Type.Element }}
 					{{ if .Type.Element.IsScalar }}
 						func (b *{{ $builderName }}) {{ $setterName }}(values ...{{ $elementType }}) *{{ $builderName }} {
+							if len(b.fieldSet_) == 0 {
+								b.fieldSet_ = make([]bool, {{ fieldSetSize $.Type }})
+							}
 							b.{{ $fieldName }} = make([]{{ $elementType }}, len(values))
 							copy(b.{{ $fieldName }}, values)
 							b.fieldSet_[{{ $fieldIndex }}] = true
@@ -318,6 +333,9 @@ func (g *BuildersGenerator) generateStructBuilderSource(typ *concepts.Type) {
 					{{ else }}
 						{{ $elementBuilderName := builderName .Type.Element }}
 						func (b *{{ $builderName }}) {{ $setterName }}(values ...*{{ selectorType . }}{{ $elementBuilderName }}) *{{ $builderName }} {
+							if len(b.fieldSet_) == 0 {
+								b.fieldSet_ = make([]bool, {{ fieldSetSize $.Type }})
+							}
 							b.{{ $fieldName }} = make([]*{{ selectorType . }}{{ $elementBuilderName }}, len(values))
 							copy(b.{{ $fieldName }}, values)
 							b.fieldSet_[{{ $fieldIndex }}] = true
@@ -330,6 +348,9 @@ func (g *BuildersGenerator) generateStructBuilderSource(typ *concepts.Type) {
 				//
 				{{ lineComment .Type.Doc }}
 				func (b *{{ $builderName }}) {{ $setterName }}(value {{ $setterType }}) *{{ $builderName }} {
+					if len(b.fieldSet_) == 0 {
+						b.fieldSet_ = make([]bool, {{ fieldSetSize $.Type }})
+					}
 					b.{{ $fieldName }} = value
 					{{ if .Type.IsScalar }}
 						b.fieldSet_[{{ $fieldIndex }}] = true

tests/go/builders_test.go

@@ -468,4 +468,52 @@ var _ = Describe("Builder", func() {
 			Expect(builder.Empty()).To(BeTrue())
 		})
 	})
+
+	Describe("Defensive initialization", func() {
+		It("Should not panic when using setter on uninitialized builder struct", func() {
+			// Create builder struct directly without using constructor
+			// This simulates the bug condition where fieldSet_ is uninitialized
+			builder := &amv1.RegistryAuthBuilder{}
+
+			// This should not panic - the setter should defensively initialize fieldSet_
+			Expect(func() {
+				builder.Username("test-user")
+			}).ToNot(Panic())
+
+			// Verify the builder can still build successfully
+			auth, err := builder.Build()
+			Expect(err).ToNot(HaveOccurred())
+			Expect(auth).ToNot(BeNil())
+			Expect(auth.Username()).To(Equal("test-user"))
+		})
+
+		It("Should handle class setters on uninitialized builder", func() {
+			// Test class-specific setters (ID, HREF, Link)
+			builder := &cmv1.ClusterBuilder{}
+
+			Expect(func() {
+				builder.ID("test-id").HREF("test-href")
+			}).ToNot(Panic())
+
+			cluster, err := builder.Build()
+			Expect(err).ToNot(HaveOccurred())
+			Expect(cluster).ToNot(BeNil())
+			Expect(cluster.ID()).To(Equal("test-id"))
+			Expect(cluster.HREF()).To(Equal("test-href"))
+		})
+
+		It("Should handle list setters on uninitialized builder", func() {
+			// Test list attribute setters with GithubIdentityProvider.Teams
+			builder := &cmv1.GithubIdentityProviderBuilder{}
+
+			Expect(func() {
+				builder.Teams("team1", "team2")
+			}).ToNot(Panic())
+
+			provider, err := builder.Build()
+			Expect(err).ToNot(HaveOccurred())
+			Expect(provider).ToNot(BeNil())
+			Expect(provider.Teams()).To(Equal([]string{"team1", "team2"}))
+		})
+	})
 })