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Fix #589: support non-scalar YAML mapping keys #715

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Fix #589: support non-scalar YAML mapping keys #715

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57bdcce
Fix #589: support non-scalar YAML mapping keys in YAMLParser
arimu1 Aug 15, 2026
d1f8bd4
Fix #589: address review feedback for complex YAML mapping keys
arimu1 Aug 15, 2026
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164 changes: 163 additions & 1 deletion yaml/src/main/java/tools/jackson/dataformat/yaml/YAMLParser.java
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Original file line number Diff line number Diff line change
Expand Up @@ -346,16 +346,42 @@ public JsonToken nextToken() throws JacksonException
if (_streamReadContext.inObject()) {
if (_currToken != JsonToken.PROPERTY_NAME) {
if (evt.getEventId() != Event.ID.Scalar) {
_currentAnchor = Optional.empty();
_lastTagEvent = null;
// end is fine
if (evt.getEventId() == Event.ID.MappingEnd) {
_currentAnchor = Optional.empty();
if (!_streamReadContext.inObject()) { // sanity check is optional, but let's do it for now
_reportMismatchedEndMarker('}', ']');
}
_streamReadContext = _streamReadContext.getParent();
return _updateToken(JsonToken.END_OBJECT);
}
// [dataformats-text#589]: complex (non-scalar) mapping keys
if (evt.getEventId() == Event.ID.SequenceStart
|| evt.getEventId() == Event.ID.MappingStart
|| evt.getEventId() == Event.ID.Alias) {
final boolean firstEntry = (_currToken == JsonToken.START_OBJECT);
if (evt.getEventId() == Event.ID.Alias) {
if (!firstEntry) {
_currentAnchor = Optional.empty();
_lastTagEvent = evt;
}
} else {
final Optional<Anchor> newAnchor = ((NodeEvent) evt).getAnchor();
if (newAnchor.isPresent() || !firstEntry) {
_currentAnchor = newAnchor;
}
if (!firstEntry) {
_lastTagEvent = evt;
}
}
final String name = _decodeComplexPropertyName(evt);
_streamReadConstraints.validateNameLength(name.length());
_currentName = name;
_streamReadContext.setCurrentName(name);
return _updateToken(JsonToken.PROPERTY_NAME);
}
_currentAnchor = Optional.empty();
_reportError("Expected a property name (Scalar value in YAML), got this instead: "+evt);
}

Expand Down Expand Up @@ -481,6 +507,142 @@ protected Event nextEvent() {
return _yamlParser.next();
}

/**
* Helper method called when a non-scalar event (Sequence or Mapping start) is encountered
* where a property name is expected -- indicates a "complex key" in YAML terms.
* Consumes the full key structure and converts to a canonical String representation
* (flow-style) so that Jackson's scalar-only property name model can represent it.
*
* @since 3.3
*/
protected String _decodeComplexPropertyName(Event evt) throws JacksonException
{
StringBuilder sb = new StringBuilder(32);
_appendComplexKey(evt, sb, 0);
return sb.toString();
}

private Event _nextComplexKeyEvent()
{
while (true) {
Event evt = nextEvent();
if (evt == null) {
return null;
}
if (evt.getEventId() == Event.ID.Comment) {
continue;
}
return evt;
}
}

private void _appendComplexKey(Event evt, StringBuilder sb, int depth) throws JacksonException
{
final int nestingDepth = _streamReadContext.getNestingDepth() + depth;
switch (evt.getEventId()) {
case Scalar:
_streamReadConstraints.validateNestingDepth(nestingDepth);
_appendComplexKeyScalar(((ScalarEvent) evt).getValue(), sb);
return;
case SequenceStart:
_streamReadConstraints.validateNestingDepth(nestingDepth);
sb.append('[');
_appendComplexKeySequenceContent(sb, depth + 1);
sb.append(']');
return;
case MappingStart:
_streamReadConstraints.validateNestingDepth(nestingDepth);
sb.append('{');
_appendComplexKeyMappingContent(sb, depth + 1);
sb.append('}');
return;
case Alias:
_streamReadConstraints.validateNestingDepth(nestingDepth);
AliasEvent alias = (AliasEvent) evt;
sb.append('*');
sb.append(alias.getAnchor().orElseThrow(() -> new RuntimeException("Alias must be provided.")).getValue());
return;
default:
_reportError("Unexpected YAML event for complex property name, expected Scalar, Sequence or Mapping start, got: "+evt);
}
}

private void _appendComplexKeySequenceContent(StringBuilder sb, int depth) throws JacksonException
{
boolean first = true;
while (true) {
Event evt = _nextComplexKeyEvent();
if (evt == null) {
_reportError("Unexpected end-of-input in complex property name (sequence)");
}
if (evt.getEventId() == Event.ID.SequenceEnd) {
return;
}
if (!first) {
sb.append(", ");
}
first = false;
_appendComplexKey(evt, sb, depth);
}
}

private void _appendComplexKeyMappingContent(StringBuilder sb, int depth) throws JacksonException
{
boolean first = true;
while (true) {
Event keyEvt = _nextComplexKeyEvent();
if (keyEvt == null) {
_reportError("Unexpected end-of-input in complex property name (mapping)");
}
if (keyEvt.getEventId() == Event.ID.MappingEnd) {
return;
}
if (!first) {
sb.append(", ");
}
first = false;
_appendComplexKey(keyEvt, sb, depth);
sb.append(": ");
Event valEvt = _nextComplexKeyEvent();
if (valEvt == null) {
_reportError("Unexpected end-of-input in complex property name (mapping value)");
}
_appendComplexKey(valEvt, sb, depth);
}
}

private void _appendComplexKeyScalar(String value, StringBuilder sb)
{
if (_needsQuotesForComplexKey(value)) {
sb.append('"');
for (int i = 0, len = value.length(); i < len; ++i) {
char c = value.charAt(i);
if (c == '"' || c == '\\') {
sb.append('\\');
}
sb.append(c);
}
sb.append('"');
} else {
sb.append(value);
}
}

private boolean _needsQuotesForComplexKey(String value)
{
if (value.isEmpty()) {
return true;
}
for (int i = 0, len = value.length(); i < len; ++i) {
char c = value.charAt(i);
if (c == ':' || c == ',' || c == '[' || c == ']' || c == '{' || c == '}'
|| c == ' ' || c == '\t' || c == '\n' || c == '\r') {
return true;
}
}
return false;
}

protected JsonToken _decodeScalar(ScalarEvent scalar) throws JacksonException
{
String value = scalar.getValue();
Expand Down
157 changes: 157 additions & 0 deletions yaml/src/test/java/tools/jackson/dataformat/yaml/deser/StreamingYAMLParseTest.java
View file
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Original file line number Diff line number Diff line change
Expand Up @@ -10,6 +10,7 @@

import tools.jackson.core.JsonParser;
import tools.jackson.core.JsonToken;
import tools.jackson.databind.JsonNode;
import tools.jackson.dataformat.yaml.JacksonYAMLParseException;
import tools.jackson.dataformat.yaml.ModuleTestBase;
import tools.jackson.dataformat.yaml.YAMLFactory;
Expand Down Expand Up @@ -663,6 +664,162 @@ public void testYamlParseFailsWhenCodePointLimitVerySmall() throws Exception
}
}

// [dataformats-text#589]: sequence (and mapping) as mapping key
@Test
public void testComplexMappingKeySequence() throws Exception
{
final String YAML = "? [user, 123]\n: name: Ivan\n age: 30\n";
try (JsonParser p = MAPPER.createParser(YAML)) {
assertToken(JsonToken.START_OBJECT, p.nextToken());
assertToken(JsonToken.PROPERTY_NAME, p.nextToken());
assertEquals("[user, 123]", p.currentName());
assertEquals("[user, 123]", p.getString());
assertToken(JsonToken.START_OBJECT, p.nextToken());
assertToken(JsonToken.PROPERTY_NAME, p.nextToken());
assertEquals("name", p.currentName());
assertToken(JsonToken.VALUE_STRING, p.nextToken());
assertEquals("Ivan", p.getString());
assertToken(JsonToken.PROPERTY_NAME, p.nextToken());
assertEquals("age", p.currentName());
assertToken(JsonToken.VALUE_NUMBER_INT, p.nextToken());
assertEquals(30, p.getIntValue());
assertToken(JsonToken.END_OBJECT, p.nextToken());
assertToken(JsonToken.END_OBJECT, p.nextToken());
assertNull(p.nextToken());
}

JsonNode node = MAPPER.readTree(YAML);
assertTrue(node.has("[user, 123]"));
assertEquals("Ivan", node.get("[user, 123]").get("name").asString());
assertEquals(30, node.get("[user, 123]").get("age").asInt());
}

@Test
public void testComplexMappingKeyMapping() throws Exception
{
final String YAML = "? {foo: bar}\n: 42\n";
try (JsonParser p = MAPPER.createParser(YAML)) {
assertToken(JsonToken.START_OBJECT, p.nextToken());
assertToken(JsonToken.PROPERTY_NAME, p.nextToken());
assertEquals("{foo: bar}", p.currentName());
assertToken(JsonToken.VALUE_NUMBER_INT, p.nextToken());
assertEquals(42, p.getIntValue());
assertToken(JsonToken.END_OBJECT, p.nextToken());
assertNull(p.nextToken());
}

JsonNode node = MAPPER.readTree(YAML);
assertTrue(node.has("{foo: bar}"));
assertEquals(42, node.get("{foo: bar}").asInt());
}

@Test
public void testComplexMappingKeyImplicitFlow() throws Exception
{
final String YAML = "[user, 123]: 42\n";
try (JsonParser p = MAPPER.createParser(YAML)) {
assertToken(JsonToken.START_OBJECT, p.nextToken());
assertToken(JsonToken.PROPERTY_NAME, p.nextToken());
assertEquals("[user, 123]", p.currentName());
assertToken(JsonToken.VALUE_NUMBER_INT, p.nextToken());
assertEquals(42, p.getIntValue());
assertToken(JsonToken.END_OBJECT, p.nextToken());
assertNull(p.nextToken());
}
}

@Test
public void testComplexMappingKeyNested() throws Exception
{
final String YAML = "? {outer: {inner: x}}\n: 42\n";
try (JsonParser p = MAPPER.createParser(YAML)) {
assertToken(JsonToken.START_OBJECT, p.nextToken());
assertToken(JsonToken.PROPERTY_NAME, p.nextToken());
assertEquals("{outer: {inner: x}}", p.currentName());
assertToken(JsonToken.VALUE_NUMBER_INT, p.nextToken());
assertEquals(42, p.getIntValue());
assertToken(JsonToken.END_OBJECT, p.nextToken());
assertNull(p.nextToken());
}
}

@Test
public void testComplexMappingKeyEmptyCollections() throws Exception
{
final String YAML = "? []\n: empty-seq\n? {}\n: empty-map\n";
try (JsonParser p = MAPPER.createParser(YAML)) {
assertToken(JsonToken.START_OBJECT, p.nextToken());

assertToken(JsonToken.PROPERTY_NAME, p.nextToken());
assertEquals("[]", p.currentName());
assertToken(JsonToken.VALUE_STRING, p.nextToken());
assertEquals("empty-seq", p.getString());

assertToken(JsonToken.PROPERTY_NAME, p.nextToken());
assertEquals("{}", p.currentName());
assertToken(JsonToken.VALUE_STRING, p.nextToken());
assertEquals("empty-map", p.getString());

assertToken(JsonToken.END_OBJECT, p.nextToken());
assertNull(p.nextToken());
}
}

@Test
public void testComplexMappingKeyQuotedSpecials() throws Exception
{
final String YAML = "? [\"a:b\", \"c,d\", has space]\n: ok\n";
try (JsonParser p = MAPPER.createParser(YAML)) {
assertToken(JsonToken.START_OBJECT, p.nextToken());
assertToken(JsonToken.PROPERTY_NAME, p.nextToken());
assertEquals("[\"a:b\", \"c,d\", \"has space\"]", p.currentName());
assertToken(JsonToken.VALUE_STRING, p.nextToken());
assertEquals("ok", p.getString());
assertToken(JsonToken.END_OBJECT, p.nextToken());
assertNull(p.nextToken());
}
}

@Test
public void testComplexMappingKeyAliasInKey() throws Exception
{
final String YAML = "? &key1 [user, 123]\n: first\n? *key1\n: second\n";
try (JsonParser p = MAPPER.createParser(YAML)) {
assertToken(JsonToken.START_OBJECT, p.nextToken());

assertToken(JsonToken.PROPERTY_NAME, p.nextToken());
assertEquals("[user, 123]", p.currentName());

assertToken(JsonToken.VALUE_STRING, p.nextToken());
assertEquals("first", p.getString());

assertToken(JsonToken.PROPERTY_NAME, p.nextToken());
assertEquals("*key1", p.currentName());

assertToken(JsonToken.VALUE_STRING, p.nextToken());
assertEquals("second", p.getString());

assertToken(JsonToken.END_OBJECT, p.nextToken());
assertNull(p.nextToken());
}
}

@Test
public void testComplexMappingKeyObjectAnchorDeferredOnFirstEntry() throws Exception
{
final String YAML = "&obj1\n? [user, 123]\n: 42\n";
YAMLParser yp = (YAMLParser) MAPPER.createParser(YAML);
assertToken(JsonToken.START_OBJECT, yp.nextToken());
assertEquals("obj1", yp.getObjectId());
assertToken(JsonToken.PROPERTY_NAME, yp.nextToken());
assertEquals("[user, 123]", yp.currentName());
assertToken(JsonToken.VALUE_NUMBER_INT, yp.nextToken());
assertEquals(42, yp.getIntValue());
assertToken(JsonToken.END_OBJECT, yp.nextToken());
assertNull(yp.nextToken());
yp.close();
}

// In Jackson 3.x, non-Number token should NOT throw exception for parser.getNumberType()
// (like in 2.x) but just return `null`
private void _verifyGetNumberTypeFail(JsonParser p, String token) throws Exception
Expand Down