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Fix W3CBaggagePropagator to allow empty baggage values per W3C spec #8468

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Fix W3CBaggagePropagator to allow empty baggage values per W3C spec #8468

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8b5d88a
Fix W3CBaggagePropagator to allow empty baggage values per W3C spec
dahyvuun Jun 10, 2026
7c54f00
Make allowEmpty field final and refactor constructor
dahyvuun Jun 11, 2026
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15 changes: 12 additions & 3 deletions api/all/src/main/java/io/opentelemetry/api/baggage/propagation/Element.java
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Original file line number Diff line number Diff line change
Expand Up @@ -31,6 +31,8 @@ class Element {
}

private final BitSet excluded;
private final boolean allowEmpty;
private boolean seenWhitespace;

@jaydeluca jaydeluca Jun 10, 2026

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i think we want to get rid of this, as right now we are accepting key1= but dropping key1= . The spec says:

Leading and trailing whitespaces (OWS) are allowed and are not considered to be a part of the value.

So i think this test needs to no longer return empty()

@jaydeluca jaydeluca Jun 11, 2026

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this is still not addressed. You can remove this entire seenWhitespace variable and related code branches, and then the extract_value_onlySpaces test needs to be updated to:

  @Test
  void extract_value_onlySpaces() {
    W3CBaggagePropagator propagator = W3CBaggagePropagator.getInstance();

    Context result =
        propagator.extract(Context.root(), ImmutableMap.of("baggage", "key1=     "), getter);
    Baggage expectedBaggage =
        Baggage.builder().put("key1", "").build();
    assertThat(Baggage.fromContext(result)).isEqualTo(expectedBaggage);
  }


private boolean leadingSpace;
private boolean readingValue;
Expand All @@ -40,20 +42,21 @@ class Element {
@Nullable private String value;

static Element createKeyElement() {
return new Element(EXCLUDED_KEY_CHARS);
return new Element(EXCLUDED_KEY_CHARS, /* allowEmpty= */ false);
}

static Element createValueElement() {
return new Element(EXCLUDED_VALUE_CHARS);
return new Element(EXCLUDED_VALUE_CHARS, /* allowEmpty= */ true);
}

/**
* Constructs element instance.
*
* @param excluded characters that are not allowed for this type of an element
*/
private Element(BitSet excluded) {
private Element(BitSet excluded, boolean allowEmpty) {
this.excluded = excluded;
this.allowEmpty = allowEmpty;
reset(0);
}

Expand All @@ -68,6 +71,7 @@ void reset(int start) {
readingValue = false;
trailingSpace = false;
value = null;
seenWhitespace = false;
}

boolean tryTerminating(int index, String header) {
Expand All @@ -77,6 +81,9 @@ boolean tryTerminating(int index, String header) {
if (this.trailingSpace) {
setValue(header);
return true;
} else if (allowEmpty && !seenWhitespace) {
this.value = "";
return true;
} else {
// leading spaces - no content, invalid
return false;
Expand Down Expand Up @@ -110,6 +117,8 @@ private static boolean isWhitespace(char character) {
private boolean tryNextWhitespace(int index) {
if (readingValue) {
markEnd(index);
} else {
seenWhitespace = true;
}
return true;
}
Expand Down
7 changes: 5 additions & 2 deletions api/all/src/test/java/io/opentelemetry/api/baggage/propagation/W3CBaggagePropagatorTest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -208,7 +208,8 @@ void extract_value_empty() {
Context result =
propagator.extract(Context.root(), ImmutableMap.of("baggage", "key1="), getter);

assertThat(Baggage.fromContext(result)).isEqualTo(Baggage.empty());
Baggage expectedBaggage = Baggage.builder().put("key1", "").build();
assertThat(Baggage.fromContext(result)).isEqualTo(expectedBaggage);
}

@Test
Expand All @@ -219,7 +220,9 @@ void extract_value_empty_withMetadata() {
propagator.extract(
Context.root(), ImmutableMap.of("baggage", "key1=;metakey=metaval"), getter);

assertThat(Baggage.fromContext(result)).isEqualTo(Baggage.empty());
Baggage expectedBaggage =
Baggage.builder().put("key1", "", BaggageEntryMetadata.create("metakey=metaval")).build();
assertThat(Baggage.fromContext(result)).isEqualTo(expectedBaggage);
}

@Test
Expand Down
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