From 3362eee2c2a6215afc05d4f5b072e7b23be642ab Mon Sep 17 00:00:00 2001
From: Joachim Van Herwegen <joachimvh@gmail.com>
Date: Tue, 1 Dec 2020 16:53:25 +0100
Subject: [PATCH] fix: Always release lock when patching

---
 src/storage/patch/SparqlUpdatePatchHandler.ts | 27 ++++++++++++-------
 .../patch/SparqlUpdatePatchHandler.test.ts    | 16 +++++++++++
 2 files changed, 34 insertions(+), 9 deletions(-)

diff --git a/src/storage/patch/SparqlUpdatePatchHandler.ts b/src/storage/patch/SparqlUpdatePatchHandler.ts
index bf85e4af9..470dfe131 100644
--- a/src/storage/patch/SparqlUpdatePatchHandler.ts
+++ b/src/storage/patch/SparqlUpdatePatchHandler.ts
@@ -65,10 +65,25 @@ export class SparqlUpdatePatchHandler extends PatchHandler {
       throw new NotImplementedHttpError('WHERE statements are not supported');
     }
 
-    // Read the quads of the current representation
     const lock = await this.locker.acquire(identifier);
-    const quads = await this.source.getRepresentation(identifier,
-      { type: [{ value: INTERNAL_QUADS, weight: 1 }]});
+    try {
+      await this.applyPatch(identifier, deletes, inserts);
+    } finally {
+      await lock.release();
+    }
+  }
+
+  private isDeleteInsert(op: Algebra.Operation): op is Algebra.DeleteInsert {
+    return op.type === Algebra.types.DELETE_INSERT;
+  }
+
+  /**
+   * Applies the given deletes and inserts to the resource.
+   */
+  private async applyPatch(identifier: ResourceIdentifier, deletes: Algebra.Pattern[], inserts: Algebra.Pattern[]):
+  Promise<void> {
+    // Read the quads of the current representation
+    const quads = await this.source.getRepresentation(identifier, { type: [{ value: INTERNAL_QUADS, weight: 1 }]});
     const store = new Store<BaseQuad>();
     const importEmitter = store.import(quads.data);
     await new Promise((resolve, reject): void => {
@@ -91,11 +106,5 @@ export class SparqlUpdatePatchHandler extends PatchHandler {
       metadata,
     };
     await this.source.setRepresentation(identifier, representation);
-
-    await lock.release();
-  }
-
-  private isDeleteInsert(op: Algebra.Operation): op is Algebra.DeleteInsert {
-    return op.type === Algebra.types.DELETE_INSERT;
   }
 }
diff --git a/test/unit/storage/patch/SparqlUpdatePatchHandler.test.ts b/test/unit/storage/patch/SparqlUpdatePatchHandler.test.ts
index 20bb3ecab..8180edf44 100644
--- a/test/unit/storage/patch/SparqlUpdatePatchHandler.test.ts
+++ b/test/unit/storage/patch/SparqlUpdatePatchHandler.test.ts
@@ -199,4 +199,20 @@ describe('A SparqlUpdatePatchHandler', (): void => {
     await expect(handle).rejects.toThrow('Only DELETE/INSERT SPARQL update operations are supported');
     expect(order).toEqual([]);
   });
+
+  it('releases the lock if an error occurs while patching.', async(): Promise<void> => {
+    source.getRepresentation = jest.fn(async(): Promise<any> => {
+      order.push('getRepresentation');
+      throw new Error('error');
+    });
+
+    const input = { identifier: { path: 'path' },
+      patch: { algebra: translate(
+        'INSERT DATA { <http://test.com/s1> <http://test.com/p1> <http://test.com/o1>. ' +
+        '<http://test.com/s2> <http://test.com/p2> <http://test.com/o2> }',
+        { quads: true },
+      ) } as SparqlUpdatePatch };
+    await expect(handler.handle(input)).rejects.toThrow('error');
+    expect(order).toEqual([ 'acquire', 'getRepresentation', 'release' ]);
+  });
 });