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

Assisted-by: GLM 5.3

encode.go

@@ -132,6 +132,10 @@ type encoder struct {
 	// their indentation.
 	inlineDepth int
 
+	// valueDepth is the nesting level of boxed containers the value writer
+	// walks, the bound a cyclic map or slice hits instead of the stack.
+	valueDepth int
+
 	// limit is the column at which an inline table is broken; only a
 	// measuring encoder raises it.
 	limit int
@@ -950,9 +954,11 @@ func addArrayValue(doc *tomlDoc, name string, v reflect.Value, path encPath, for
 	return nil
 }
 
-// writeArrayValue writes a value array from its reflect value, its elements
+// writeArrayValue writes a value array from its reflect value. Only the
-// written one by one, each falling back to the boxed path only where the
+// plain scalar kinds reach it: addArrayValue's direct path takes nothing but
-// boxed rules rewrite it.
+// arrays whose elements are scalar kinds without methods, so one writer per
+// element needs no boxing branch and no depth walk of its own; the slices
+// and maps the boxed rules re-write travel the normaliseValue route.
 func (e *encoder) writeArrayValue(v reflect.Value, depth int) error {
 	if atDepthLimit(depth) {
 		return errDepthLimit()
@@ -962,7 +968,7 @@ func (e *encoder) writeArrayValue(v reflect.Value, depth int) error {
 		if i > 0 {
 			e.buf.WriteString(", ")
 		}
-		if err := e.writeArrayElem(v.Index(i), depth+1); err != nil {
+		if err := e.writeScalarValue(v.Index(i)); err != nil {
 			return err
 		}
 	}
@@ -970,129 +976,6 @@ func (e *encoder) writeArrayValue(v reflect.Value, depth int) error {
 	return nil
 }
 
-// writeArrayElem writes one element of a value array. The kinds the boxed
-// rules rewrite are handed to normaliseValue and the boxed writer; the rest
-// write directly, including nested arrays and inline tables.
-func (e *encoder) writeArrayElem(v reflect.Value, depth int) error {
-	if v.Kind() == reflect.Interface {
-		if v.IsNil() {
-			return fmt.Errorf("interpres: cannot encode nil value")
-		}
-		v = v.Elem()
-	}
-	switch v.Kind() {
-	case reflect.Slice, reflect.Array:
-		return e.writeArrayValue(v, depth)
-	case reflect.Map:
-		return e.writeInlineMapFromReflect(v, depth)
-	}
-	if _, isMarshaler := marshalerOf(v); isMarshaler {
-		return e.writeNormalisedElem(v, depth)
-	}
-	if _, isText, err := textValue(v); err != nil || isText {
-		if err != nil {
-			return err
-		}
-		return e.writeNormalisedElem(v, depth)
-	}
-	switch v.Kind() {
-	case reflect.String, reflect.Bool, reflect.Int, reflect.Int8, reflect.Int16,
-		reflect.Int32, reflect.Int64, reflect.Uint, reflect.Uint8, reflect.Uint16,
-		reflect.Uint32, reflect.Uint64, reflect.Float32, reflect.Float64:
-		if t := v.Type(); t != durationType && t != numberType {
-			return e.writeScalarValue(v)
-		}
-	}
-	return e.writeNormalisedElem(v, depth)
-}
-
-// writeNormalisedElem normalises one element through the boxed rules and
-// writes the result.
-func (e *encoder) writeNormalisedElem(v reflect.Value, depth int) error {
-	val, err := normaliseValueAt(v, depth)
-	if err != nil {
-		return err
-	}
-	return e.writeValue(val)
-}
-
-// writeInlineMapFromReflect renders a map from its reflect value as an inline
-// table, the shape the boxed path gives the table elements of a value array:
-// sorted keys, single line when it fits, across lines when it does not.
-func (e *encoder) writeInlineMapFromReflect(v reflect.Value, depth int) error {
-	if e.limit >= noInlineBreak {
-		return e.writeInlineMapFlatReflect(v, depth)
-	}
-	flat := e.flat()
-	err := flat.writeInlineMapFlatReflect(v, depth)
-	if err != nil {
-		flat.release()
-		return err
-	}
-	fits := e.column()+flat.buf.Len() <= e.limit
-	if fits {
-		e.buf.Write(flat.buf.Bytes())
-	}
-	flat.release()
-	if fits {
-		return nil
-	}
-	return e.writeInlineMapMultilineReflect(v, depth)
-}
-
-// writeInlineMapFlatReflect renders the single-line form.
-func (e *encoder) writeInlineMapFlatReflect(v reflect.Value, depth int) error {
-	if v.Type().Key().Kind() != reflect.String {
-		return fmt.Errorf("map key must be string, got %s", v.Type().Key())
-	}
-	keys := make([]string, 0, v.Len())
-	for _, k := range v.MapKeys() {
-		keys = append(keys, k.String())
-	}
-	slices.Sort(keys)
-	e.buf.WriteByte('{')
-	for i, k := range keys {
-		if i > 0 {
-			e.buf.WriteString(", ")
-		}
-		if err := e.writeKey(k); err != nil {
-			return err
-		}
-		e.buf.WriteString(" = ")
-		if err := e.writeArrayElem(v.MapIndex(reflect.ValueOf(k)), depth+1); err != nil {
-			return err
-		}
-	}
-	e.buf.WriteByte('}')
-	return nil
-}
-
-// writeInlineMapMultilineReflect renders the across-lines form.
-func (e *encoder) writeInlineMapMultilineReflect(v reflect.Value, depth int) error {
-	keys := make([]string, 0, v.Len())
-	for _, k := range v.MapKeys() {
-		keys = append(keys, k.String())
-	}
-	slices.Sort(keys)
-	e.buf.WriteString("{\n")
-	e.inlineDepth++
-	for _, k := range keys {
-		e.writeInlineIndent()
-		if err := e.writeKey(k); err != nil {
-			return err
-		}
-		e.buf.WriteString(" = ")
-		if err := e.writeArrayElem(v.MapIndex(reflect.ValueOf(k)), depth+1); err != nil {
-			return err
-		}
-		e.buf.WriteString(",\n")
-	}
-	e.inlineDepth--
-	e.writeInlineIndent()
-	e.buf.WriteByte('}')
-	return nil
-}
-
 // marshalerOf finds the Marshaler a value carries: on the value itself, or on
 // its address, so a pointer-receiver MarshalTOML is found on an addressable
 // struct field or slice element, exactly as textMarshalerOf finds MarshalText.
@@ -1364,7 +1247,13 @@ func textMarshalerOf(v reflect.Value) (encoding.TextMarshaler, bool) {
 	return nil, false
 }
 
+// isTableElementType reports whether a slice of t is an array of tables. A
+// pointer element is looked through, so []*T behaves as []T: the empty-slice
+// decision and the header form agree on the same element type.
 func isTableElementType(t reflect.Type) bool {
+	for t.Kind() == reflect.Pointer {
+		t = t.Elem()
+	}
 	switch t.Kind() {
 	case reflect.Struct:
 		return !isScalarStruct(t) && !isTextMarshalerType(t)
@@ -1395,12 +1284,24 @@ func (e *encoder) writeBlankLine() {
 }
 
 func (e *encoder) emitDoc(doc *tomlDoc, prefix []string) error {
+	// The walk that built the document checked the context on its own
+	// cadence; the emission of a large document is long enough to need the
+	// same checks, or a cancellation that lands after the walk would wait a
+	// full document out.
+	if err := e.checkCtx(); err != nil {
+		return err
+	}
 	if e.opts.layout == LayoutKindGrouped {
 		// Scalars first, then inline sub-tables as value lines, then the
 		// remaining tables as headers, then arrays of tables. Each pass walks
 		// the entries in place; grouping copies of them cost the encoder a
 		// third of its allocations for nothing.
 		for i := range doc.entries {
+			if i%ctxCheckInterval == 0 {
+				if err := e.checkCtx(); err != nil {
+					return err
+				}
+			}
 			kv := &doc.entries[i]
 			if kv.kind != entryScalar {
 				continue
@@ -1413,6 +1314,11 @@ func (e *encoder) emitDoc(doc *tomlDoc, prefix []string) error {
 		// header of this document: a line written after a [header] would be
 		// read back as part of that table.
 		for i := range doc.entries {
+			if i%ctxCheckInterval == 0 {
+				if err := e.checkCtx(); err != nil {
+					return err
+				}
+			}
 			t := &doc.entries[i]
 			if t.kind != entryTable {
 				continue
@@ -1424,6 +1330,11 @@ func (e *encoder) emitDoc(doc *tomlDoc, prefix []string) error {
 			t.emitted = inlined
 		}
 		for i := range doc.entries {
+			if i%ctxCheckInterval == 0 {
+				if err := e.checkCtx(); err != nil {
+					return err
+				}
+			}
 			t := &doc.entries[i]
 			if t.kind != entryTable || t.emitted {
 				continue
@@ -1441,12 +1352,22 @@ func (e *encoder) emitDoc(doc *tomlDoc, prefix []string) error {
 			}
 		}
 		for i := range doc.entries {
+			if i%ctxCheckInterval == 0 {
+				if err := e.checkCtx(); err != nil {
+					return err
+				}
+			}
 			a := &doc.entries[i]
 			if a.kind != entryArray {
 				continue
 			}
 			path := append(append([]string{}, prefix...), a.key)
 			for j, sub := range a.docs {
+				if j%ctxCheckInterval == 0 {
+					if err := e.checkCtx(); err != nil {
+						return err
+					}
+				}
 				e.writeBlankLine()
 				if j == 0 {
 					e.writeComments(a.comments)
@@ -1469,7 +1390,12 @@ func (e *encoder) emitDoc(doc *tomlDoc, prefix []string) error {
 	// own section content; the emitter still writes sub-documents as separate
 	// nested blocks, so a "" sub-keyed scalar following a header for the same
 	// section is impossible in practice (struct fields are visited in order).
-	for _, ent := range doc.entries {
+	for i, ent := range doc.entries {
+		if i%ctxCheckInterval == 0 {
+			if err := e.checkCtx(); err != nil {
+				return err
+			}
+		}
 		switch ent.kind {
 		case entryScalar:
 			if err := e.writeKV(&ent); err != nil {
@@ -1699,9 +1625,15 @@ func (e *encoder) writeValue(val any) error {
 	case float64:
 		return e.writeFloat(v)
 	case time.Time:
+		if err := wholeMinuteOffset(v); err != nil {
+			return err
+		}
 		e.buf.WriteString(offsetString(v))
 		return nil
 	case OffsetDateTime:
+		if err := wholeMinuteOffset(v.Time); err != nil {
+			return err
+		}
 		e.buf.WriteString(v.String())
 		return nil
 	case LocalDateTime:
@@ -1714,19 +1646,19 @@ func (e *encoder) writeValue(val any) error {
 		e.buf.WriteString(v.String())
 		return nil
 	case []any:
-		e.buf.WriteByte('[')
+		if err := e.enterValueDepth(); err != nil {
-		for i, item := range v {
+			return err
-			if i > 0 {
-				e.buf.WriteString(", ")
-			}
-			if err := e.writeValue(item); err != nil {
-				return err
-			}
 		}
-		e.buf.WriteByte(']')
+		err := e.writeValueArray(v)
-		return nil
+		e.valueDepth--
+		return err
 	case map[string]any:
-		return e.writeInlineMap(v)
+		if err := e.enterValueDepth(); err != nil {
+			return err
+		}
+		err := e.writeInlineMap(v)
+		e.valueDepth--
+		return err
 	case nil:
 		return fmt.Errorf("interpres: cannot encode nil value")
 	default:
@@ -1734,6 +1666,32 @@ func (e *encoder) writeValue(val any) error {
 	}
 }
 
+// enterValueDepth counts one level of boxed container nesting. The
+// reflection walk has its own bound, but a tree built by hand and written
+// through the boxed path carries no walk, so the writer bounds itself.
+func (e *encoder) enterValueDepth() error {
+	e.valueDepth++
+	if e.valueDepth > maxEncodeDepth {
+		return errDepthLimit()
+	}
+	return nil
+}
+
+// writeValueArray writes a boxed value array, one writeValue per element.
+func (e *encoder) writeValueArray(v []any) error {
+	e.buf.WriteByte('[')
+	for i, item := range v {
+		if i > 0 {
+			e.buf.WriteString(", ")
+		}
+		if err := e.writeValue(item); err != nil {
+			return err
+		}
+	}
+	e.buf.WriteByte(']')
+	return nil
+}
+
 // writeInlineMap renders m as a TOML inline table, on one line when it fits
 // there and across lines when it does not.
 func (e *encoder) writeInlineMap(m map[string]any) error {

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)
+	}
+}