namedgraph opened a new issue, #4091:
URL: https://github.com/apache/jena/issues/4091
## Version
6.0.0 and 6.1.0 (current release). Works in 5.6.0. Still present on `main`
(by code inspection, links below).
Environment: macOS (arm64), OpenJDK 25.0.1 (Homebrew).
## What happened
The `arq` CLI can no longer output the result of a quad `CONSTRUCT { GRAPH …
{ … } }` query (the ARQ syntax extension) in **any** format — the default
output path throws, and the dataset-capable `--results` formats were dropped.
Minimal repro, no data files needed:
```shell
echo 'CONSTRUCT { GRAPH <urn:x:g> { <urn:x:s> <urn:x:p> <urn:x:o> } } WHERE
{}' > quads.rq
apache-jena-5.6.0/bin/arq --query quads.rq # exit 0:
# <urn:x:g> {
# <urn:x:s> <urn:x:p> <urn:x:o> .
# }
apache-jena-6.1.0/bin/arq --query quads.rq # exit 2 (same on 6.0.0):
# org.apache.jena.riot.RiotException: No dataset writer for Turtle_pretty
```
Full stack trace on 6.1.0:
```
org.apache.jena.riot.RiotException: No dataset writer for Turtle_pretty
at
org.apache.jena.riot.RDFWriter.createDatasetWriter$(RDFWriter.java:253)
at org.apache.jena.riot.RDFWriter.write$(RDFWriter.java:263)
at org.apache.jena.riot.RDFWriter.output(RDFWriter.java:222)
at org.apache.jena.riot.RDFWriter.output(RDFWriter.java:161)
at
org.apache.jena.riot.RDFWriterBuilder.output(RDFWriterBuilder.java:213)
at
org.apache.jena.sparql.util.QueryExecUtils.writeDataset(QueryExecUtils.java:282)
at
org.apache.jena.sparql.util.QueryExecUtils.doConstructQuadsQuery(QueryExecUtils.java:250)
at
org.apache.jena.sparql.util.QueryExecUtils.executeQuery(QueryExecUtils.java:124)
at arq.query.lambda$queryExec$0(query.java:248)
at org.apache.jena.system.Txn.exec(Txn.java:82)
at org.apache.jena.system.Txn.executeRead(Txn.java:120)
at arq.query.queryExec(query.java:244)
at arq.query.exec(query.java:161)
at org.apache.jena.cmd.CmdMain.mainMethod(CmdMain.java:98)
at org.apache.jena.cmd.CmdMain.mainRun(CmdMain.java:64)
at org.apache.jena.cmd.CmdMain.mainRun(CmdMain.java:52)
at arq.arq.main(arq.java:31)
```
There is no workaround from the CLI:
- `--results=trig` / `--results=nq` → `Unrecognized output format` in 6.x
(5.6.0 accepted `trig`)
- `--results=text` → the same exception as the default
- `--syntax=arq` changes nothing — parsing and execution succeed (the stack
reaches `doConstructQuadsQuery`); the failure is purely in output-writer
selection
So pipelines that use `arq` for quad CONSTRUCT are pinned to Jena ≤ 5.6.0.
## Analysis
Introduced by the 6.0.0 `ResultsFormat` rewrite (symbol registry → enum):
- The default results format `TEXT` carries `RDFFormat.TURTLE`
([ResultsFormat.java#L43](https://github.com/apache/jena/blob/jena-6.1.0/jena-arq/src/main/java/org/apache/jena/sparql/resultset/ResultsFormat.java#L43)).
- `QueryExecUtils.writeDataset` passes `outputFormat.rdfFormat()` straight
to `RDFWriter`
([QueryExecUtils.java#L278-L284](https://github.com/apache/jena/blob/jena-6.1.0/jena-arq/src/main/java/org/apache/jena/sparql/util/QueryExecUtils.java#L278-L284));
Turtle has no dataset writer → `RiotException`.
- No enum constant carries a dataset-capable `RDFFormat`, and the
`trig`/`nquads` name registrations are commented out
([ResultsFormat.java#L167-L169](https://github.com/apache/jena/blob/jena-6.1.0/jena-arq/src/main/java/org/apache/jena/sparql/resultset/ResultsFormat.java#L167-L169))
— so TriG/N-Quads output is unreachable. Unchanged on `main`.
Related regression from the same rewrite: for a plain (triples) CONSTRUCT,
`writeModel` hardcodes `RDFFormat.TURTLE_PRETTY` and ignores the requested
format
([QueryExecUtils.java#L272-L276](https://github.com/apache/jena/blob/jena-6.1.0/jena-arq/src/main/java/org/apache/jena/sparql/util/QueryExecUtils.java#L272-L276)):
```shell
echo 'CONSTRUCT { <urn:x:s> <urn:x:p> <urn:x:o> } WHERE {}' > triples.rq
apache-jena-6.1.0/bin/arq --query triples.rq --results=rdfxml # exit 0:
# <urn:x:s> <urn:x:p> <urn:x:o> .
```
Turtle, not the requested RDF/XML. (5.6.0 rejected the unsupported name
outright with `Unrecognized output format: rdfxml`, exit 5 — 6.x accepts it and
silently ignores it.)
## Self-contained repro script
Downloads 5.6.0 / 6.0.0 / 6.1.0 from archive.apache.org and prints the full
matrix (default quad output, `--results=trig`, `--results=rdfxml`) per version:
<details>
<summary>jena-quad-construct-repro.sh</summary>
```shell
#!/usr/bin/env bash
# Minimal repro: `arq` cannot output quad CONSTRUCT results in Apache Jena
6.x.
# 5.6.0: emits TriG, exit 0
# 6.0.0/6.1.0: org.apache.jena.riot.RiotException: No dataset writer for
Turtle_pretty, exit 2
# Usage: ./jena-quad-construct-repro.sh [workdir] (default
/tmp/jena-quad-repro)
# Requires: curl, tar, Java 21+ (Jena 6.x requirement).
set -uo pipefail
WORK="${1:-/tmp/jena-quad-repro}"
VERSIONS=(5.6.0 6.0.0 6.1.0)
MIRROR=https://archive.apache.org/dist/jena/binaries
mkdir -p "$WORK"
cd "$WORK"
for v in "${VERSIONS[@]}"; do
[ -d "apache-jena-$v" ] && continue
echo "downloading apache-jena-$v ..." >&2
curl -fsSL -o "apache-jena-$v.tar.gz" "$MIRROR/apache-jena-$v.tar.gz"
tar xzf "apache-jena-$v.tar.gz"
done
cat > quads.rq <<'EOF'
CONSTRUCT { GRAPH <urn:x:g> { <urn:x:s> <urn:x:p> <urn:x:o> } } WHERE {}
EOF
cat > triples.rq <<'EOF'
CONSTRUCT { <urn:x:s> <urn:x:p> <urn:x:o> } WHERE {}
EOF
# NB: bin/arq honors a pre-set JENA_HOME when building the classpath, so a
stray
# export runs a DIFFERENT version's jars than the script path suggests — pin
it.
run() {
local v=$1; shift
env JENA_HOME="$WORK/apache-jena-$v" "$WORK/apache-jena-$v/bin/arq" "$@"
}
for v in "${VERSIONS[@]}"; do
echo "================ Apache Jena $v ================"
echo "--- quad CONSTRUCT, default output ---"
run "$v" --query quads.rq 2>&1 | head -4
echo "exit=${PIPESTATUS[0]}"
echo "--- quad CONSTRUCT, --results=trig ---"
run "$v" --query quads.rq --results=trig 2>&1 | head -4
echo "exit=${PIPESTATUS[0]}"
echo "--- triples CONSTRUCT, --results=rdfxml ---"
run "$v" --query triples.rq --results=rdfxml 2>&1 | head -4
echo "exit=${PIPESTATUS[0]}"
echo
done
```
</details>
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