fix(extract): a fenced answer is not discarded for an earlier object or a brace in prose

Closes #363. The JSON locator behind `extract` took the first object that parsed,
in every port. A draft object in the model's reasoning, an echoed format example
(`{"topic": "<slug>"}`) or prose with a brace (`{a set}`) therefore won, the
complete answer in the following ```json fence was never read, and with its
@required fields missing the reply was reported unusable: silently discarded,
not mis-parsed.

Selection now searches every fenced block first, then the whole reply, and takes
the first object that carries at least one declared field. A fenced object with
none of them (a fenced example) falls through the same way, so it cannot shadow
an unfenced answer either. When no object carries a declared field, the old
first-closed-else-first-open rule decides, so every reply that parsed before
parses the same and all 33 existing corpus cases keep their outcome.

Five new extract-conformance cases, from the issue's rows plus the two
fall-through directions, fail on the old locator and pass in all four engines
(Kotlin runs the Java one): TS 164, Java 298, C# 296, Python 204 extract tests.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01M1mRRB1K2WdYy82kntMQdx

Author: dmealing

CHANGELOG.md

@@ -10,6 +10,22 @@ here.**
 
 ## [Unreleased]
 
+### Fixed
+
+- **`extract` no longer discards a fenced answer that follows an earlier object or a brace in
+  prose ([#363]), in every port.** The JSON locator took the first object that parsed, so a
+  draft object in the model's reasoning, an echoed format example (`{"topic": "<slug>"}`) or
+  plain prose with a brace (`{a set}`) won, and the complete answer in the following
+  ```` ```json ```` fence was never read; with its `@required` fields missing, the reply
+  was reported unusable. The locator now searches fenced blocks first, then the whole reply,
+  and takes the first object that carries at least one declared field. A fenced object with
+  none of them (a fenced example) falls through the same way. When no object carries a
+  declared field, the old first-object rule decides, so every reply that parsed before parses
+  the same. Five new `extract-conformance` cases pin the behaviour in all four engines
+  (Kotlin runs the Java one).
+
+[#363]: https://github.com/metaobjectsdev/metaobjects/issues/363
+
 ## [1.0.6] — 2026-09-23
 
 _Maven Central `8.0.6` only. npm, PyPI and NuGet have no product change and stay at `1.0.5`

docs/CONFORMANCE.md

@@ -31,7 +31,7 @@ regenerate with `ls -d fixtures/<corpus>/*/ | wc -l` for directory-shaped corpor
 | [`fixtures/verify-conformance/`](../fixtures/verify-conformance/) | 31 | ✓ | ✓ | inherits via Java | ✓ | ✓ |
 | [`fixtures/verify-strict-conformance/`](../fixtures/verify-strict-conformance/) | 1 | ✓ | — | — | — | ✓ |
 | [`fixtures/render-conformance/`](../fixtures/render-conformance/) | 15 | ✓ | ✓ | inherits via Java | ✓ | ✓ |
-| [`fixtures/extract-conformance/`](../fixtures/extract-conformance/) | 33 | ✓ | ✓ | inherits the shared JVM engine | ✓ | ✓ |
+| [`fixtures/extract-conformance/`](../fixtures/extract-conformance/) | 38 | ✓ | ✓ | inherits the shared JVM engine | ✓ | ✓ |
 | [`fixtures/output-prompt-conformance/`](../fixtures/output-prompt-conformance/) | 14 | ✓ | ✓ | ✓ | ✓ | ✓ |
 | [`fixtures/persistence-conformance/`](../fixtures/persistence-conformance/) | 33 (27 query + 6 migration) | all 33 | 27 query (migrations TS-only, ADR-0015) | 27 query (via Exposed) | 27 query | 27 query |
 | [`fixtures/api-contract-conformance/`](../fixtures/api-contract-conformance/) | 61 (31 core + 10 tph + 9 m2m + 2 jsonb + 2 write-through + 7 projection) | ✓ (Fastify reference + generated lane) | ✓ (embedded HTTP + JDBC) | ✓ (embedded HTTP + Exposed) | ✓ (HttpListener + Npgsql) | ✓ (FastAPI + pg8000) |

fixtures/extract-conformance/README.md

@@ -44,3 +44,8 @@ Each `fields[]` entry: `name`, `kind` (`STRING|INT|LONG|DOUBLE|BOOLEAN|ENUM|OBJE
 
 FR-011 added the `enum-*`, `nested-object-*`, `array-of-objects`, `xml-nested`, and
 `multi-malformation` cases on top of the original FR-010 ten.
+
+#363 added the three `json-fence-after-*` cases, `json-fenced-example-then-answer` and
+`json-shapeless-object-then-answer` cases: JSON selection searches fenced blocks first, then
+the whole reply, and takes the first object carrying at least one declared field; only when
+none does is the first object taken.

fixtures/extract-conformance/json-fence-after-draft-object/expected.json

@@ -0,0 +1 @@
+{ "empty": false, "states": { "topic": "EXTRACTED", "worth_forming": "EXTRACTED", "reason": "EXTRACTED" }, "data": { "topic": "real", "worth_forming": true, "reason": "r" } }

fixtures/extract-conformance/json-fence-after-draft-object/input.txt

@@ -0,0 +1,4 @@
+{"topic":"draft_idea"}
+```json
+{"topic":"real","worth_forming":true,"reason":"r"}
+```

fixtures/extract-conformance/json-fence-after-draft-object/schema.json

@@ -0,0 +1,4 @@
+{ "format": "JSON", "rootName": "gate", "fields": [
+  { "name": "topic",         "kind": "STRING",  "required": false },
+  { "name": "worth_forming", "kind": "BOOLEAN", "required": true },
+  { "name": "reason",        "kind": "STRING",  "required": true } ] }

fixtures/extract-conformance/json-fence-after-format-echo/expected.json

@@ -0,0 +1 @@
+{ "empty": false, "states": { "topic": "EXTRACTED", "worth_forming": "EXTRACTED", "reason": "EXTRACTED" }, "data": { "topic": "real", "worth_forming": true, "reason": "r" } }

fixtures/extract-conformance/json-fence-after-format-echo/input.txt

@@ -0,0 +1,4 @@
+The format is {"topic": "<slug>"}.
+```json
+{"topic":"real","worth_forming":true,"reason":"r"}
+```

fixtures/extract-conformance/json-fence-after-format-echo/schema.json

@@ -0,0 +1,4 @@
+{ "format": "JSON", "rootName": "gate", "fields": [
+  { "name": "topic",         "kind": "STRING",  "required": false },
+  { "name": "worth_forming", "kind": "BOOLEAN", "required": true },
+  { "name": "reason",        "kind": "STRING",  "required": true } ] }

fixtures/extract-conformance/json-fence-after-prose-brace/expected.json

@@ -0,0 +1 @@
+{ "empty": false, "states": { "topic": "EXTRACTED", "worth_forming": "EXTRACTED", "reason": "EXTRACTED" }, "data": { "topic": "real", "worth_forming": true, "reason": "r" } }