fix(encode): pointer table arrays, whole-minute offsets and emission checks

Assisted-by: GLM 5.3

encode_test.go

@@ -67,7 +67,7 @@ func TestMarshalFloatSpecials(t *testing.T) {
 	}
 }
 
-func TestMarshalFloatNormalizesNegativeZero(t *testing.T) {
+func TestMarshalFloatNormalisesNegativeZero(t *testing.T) {
 	// The output contract normalises negative zero to "0.0".
 	type Cfg struct {
 		Z float64 `toml:"z"`
@@ -2284,3 +2284,115 @@ func TestEmitFieldComments(t *testing.T) {
 		}
 	})
 }
+
+// errWriter fails every write with a fixed error.
+type errWriter struct{ err error }
+
+func (w errWriter) Write([]byte) (int, error) { return 0, w.err }
+
+// TestMarshalWrite covers the streaming entry: the happy path with options
+// and a failing writer.
+func TestMarshalWrite(t *testing.T) {
+	var buf bytes.Buffer
+	err := MarshalWrite(&buf, map[string]any{"b": 2, "a": 1})
+	if err != nil {
+		t.Fatalf("MarshalWrite: %v", err)
+	}
+	// A map carries no order, so the writer uses the sorted one.
+	if buf.String() != "a = 1\nb = 2\n" {
+		t.Errorf("output = %q", buf.String())
+	}
+	writeErr := errors.New("boom")
+	if err := MarshalWrite(errWriter{writeErr}, map[string]any{"a": 1}); !errors.Is(err, writeErr) {
+		t.Errorf("err = %v, want the write error wrapped", err)
+	}
+}
+
+// TestMarshalRejectsUnsupportedKinds pins the clear error a field of a kind
+// TOML cannot carry raises, through the struct walk.
+func TestMarshalRejectsUnsupportedKinds(t *testing.T) {
+	tests := []struct {
+		name  string
+		value any
+	}{
+		{"func", struct {
+			F func() `toml:"f"`
+		}{}},
+		{"chan", struct {
+			C chan int `toml:"c"`
+		}{}},
+		{"complex", struct {
+			Z complex128 `toml:"z"`
+		}{}},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			_, err := Marshal(tt.value)
+			if err == nil {
+				t.Fatalf("Marshal accepted %#v", tt.value)
+			}
+			if !strings.Contains(err.Error(), "cannot encode") {
+				t.Errorf("err = %v, want the cannot-encode complaint", err)
+			}
+		})
+	}
+}
+
+// TestMarshalOmitsEmptyPointerTableSlice pins that an empty slice of pointer
+// tables is omitted, the rule its non-pointer form already follows.
+func TestMarshalOmitsEmptyPointerTableSlice(t *testing.T) {
+	type item struct {
+		N int `toml:"n"`
+	}
+	out, err := Marshal(struct {
+		Items []*item `toml:"items"`
+	}{})
+	if err != nil {
+		t.Fatalf("Marshal: %v", err)
+	}
+	if len(out) != 0 {
+		t.Errorf("output = %q, want the empty array of tables omitted", out)
+	}
+}
+
+// TestMarshalRejectsNonWholeMinuteOffset pins that a zone offset carrying
+// seconds is refused instead of silently losing them.
+func TestMarshalRejectsNonWholeMinuteOffset(t *testing.T) {
+	z := time.FixedZone("", 57*60+44)
+	_, err := Marshal(struct {
+		Stamp time.Time `toml:"stamp"`
+	}{Stamp: time.Date(1890, 1, 1, 12, 0, 0, 0, z)})
+	if err == nil || !strings.Contains(err.Error(), "not a whole number of minutes") {
+		t.Errorf("err = %v, want the whole-minute offset complaint", err)
+	}
+	_, err = Marshal(struct {
+		Stamp OffsetDateTime `toml:"stamp"`
+	}{Stamp: OffsetDateTime{time.Date(1890, 1, 1, 12, 0, 0, 0, z)}})
+	if err == nil || !strings.Contains(err.Error(), "not a whole number of minutes") {
+		t.Errorf("err = %v, want the whole-minute offset complaint for the wrapper", err)
+	}
+}
+
+// cancelOnMarshal cancels the context the encode runs under, the moment its
+// method is called, so the emission that follows is already past the walk's
+// own checks.
+type cancelOnMarshal struct {
+	cancel context.CancelFunc
+}
+
+func (c cancelOnMarshal) MarshalTOML() (any, error) {
+	c.cancel()
+	return int64(1), nil
+}
+
+// TestMarshalContextCancelsDuringEmission pins that a context cancelled
+// between the walk and the emission stops the encode instead of writing the
+// whole document out.
+func TestMarshalContextCancelsDuringEmission(t *testing.T) {
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	value := map[string]any{"k": cancelOnMarshal{cancel}}
+	if _, err := MarshalContext(ctx, value); !errors.Is(err, context.Canceled) {
+		t.Errorf("err = %v, want the cancellation", err)
+	}
+}