fix nil-aware ok return in jws header accessors (#1818)

* fix nil-aware ok return in jws header accessors

* make headers nil-accessor subtests parallel

Author: lestrrat

jws/headers_gen.go

@@ -0,0 +1,41 @@
+package jws_test
+
+import (
+	"testing"
+
+	"github.com/lestrrat-go/jwx/v3/jws"
+	"github.com/stretchr/testify/require"
+)
+
+// A freshly constructed Headers must report ok=false on every typed
+// accessor for a field that has never been set. This is a regression
+// guard for the genjws generator where slice/interface accessors used
+// to unconditionally return ok=true.
+func TestHeaders_NilAccessorsReportNotPresent(t *testing.T) {
+	t.Parallel()
+
+	testcases := []struct {
+		name string
+		get  func(jws.Headers) (any, bool)
+	}{
+		{"Algorithm", func(h jws.Headers) (any, bool) { v, ok := h.Algorithm(); return v, ok }},
+		{"ContentType", func(h jws.Headers) (any, bool) { v, ok := h.ContentType(); return v, ok }},
+		{"Critical", func(h jws.Headers) (any, bool) { v, ok := h.Critical(); return v, ok }},
+		{"JWK", func(h jws.Headers) (any, bool) { v, ok := h.JWK(); return v, ok }},
+		{"JWKSetURL", func(h jws.Headers) (any, bool) { v, ok := h.JWKSetURL(); return v, ok }},
+		{"KeyID", func(h jws.Headers) (any, bool) { v, ok := h.KeyID(); return v, ok }},
+		{"Type", func(h jws.Headers) (any, bool) { v, ok := h.Type(); return v, ok }},
+		{"X509CertChain", func(h jws.Headers) (any, bool) { v, ok := h.X509CertChain(); return v, ok }},
+		{"X509CertThumbprint", func(h jws.Headers) (any, bool) { v, ok := h.X509CertThumbprint(); return v, ok }},
+		{"X509CertThumbprintS256", func(h jws.Headers) (any, bool) { v, ok := h.X509CertThumbprintS256(); return v, ok }},
+		{"X509URL", func(h jws.Headers) (any, bool) { v, ok := h.X509URL(); return v, ok }},
+	}
+
+	for _, tc := range testcases {
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+			_, ok := tc.get(jws.NewHeaders())
+			require.False(t, ok)
+		})
+	}
+}

jws/headers_nil_test.go

@@ -165,7 +165,7 @@ func generateHeaders(obj *codegen.Object) error {
 			o.L("}")
 			o.L("return *(h.%s), true", f.Name(false))
 		} else {
-			o.L("return h.%s, true", f.Name(false))
+			o.L("return h.%[1]s, h.%[1]s != nil", f.Name(false))
 		}
 		o.L("}") // func (h *stdHeaders) %s() %s
 	}