Bail out when chain detection is expensive + edge case fix

src/rdf.test.ts

@@ -587,7 +587,7 @@ describe("fromRdfJsDataset", () => {
       );
     });
 
-    it("can parse chained Blank Nodes with a single lnk that end in a dangling Blank Node", () => {
+    it("can parse chained Blank Nodes with a single link that end in a dangling Blank Node", () => {
       const mockDataset: ImmutableDataset = {
         type: "Dataset",
         graphs: { default: {} },

src/rdfjs.internal.ts

@@ -502,9 +502,11 @@ function getCycleBlankNodes(
     )
     .map((quad) => quad.object as RdfJs.BlankNode);
 
-  // If no Blank Nodes are connected to `currentNode`, we're done:
+  // If no Blank Nodes are connected to `currentNode`, and `currentNode` is not
+  // part of a cycle, we're done; the currently traversed Nodes do not form a
+  // cycle:
   if (blankNodeObjects.length === 0) {
-    return traversedBlankNodes;
+    return [];
   }
 
   // Store that we've traversed `currentNode`, then move on to all the Blank

src/resource/solidDataset.test.ts

@@ -167,6 +167,155 @@ describe("responseToSolidDataset", () => {
     });
   });
 
+  it("does not include non-deterministic identifiers when it detects non-cyclic chains of Blank Nodes", async () => {
+    const turtle = `
+      @prefix : <#>.
+      @prefix foaf: <http://xmlns.com/foaf/0.1/>.
+      @prefix vcard: <http://www.w3.org/2006/vcard/ns#>.
+      @prefix acl: <http://www.w3.org/ns/auth/acl#>.
+
+      <> a foaf:PersonalProfileDocument; foaf:maker :me; foaf:primaryTopic :me.
+
+      :me
+        a foaf:Person;
+        vcard:fn "Vincent";
+        acl:trustedApp
+          [
+            acl:mode acl:Append, acl:Control, acl:Read, acl:Write;
+            acl:origin <http://localhost:3000>
+          ],
+          [
+            acl:mode acl:Append, acl:Control, acl:Read, acl:Write;
+            acl:origin <https://penny.vincenttunru.com>
+          ].
+    `;
+
+    const response = new Response(turtle, {
+      headers: {
+        "Content-Type": "text/turtle",
+      },
+    });
+    jest
+      .spyOn(response, "url", "get")
+      .mockReturnValue("https://some.pod/resource");
+    const solidDataset = await responseToSolidDataset(response);
+
+    expect(solidDataset).toStrictEqual({
+      graphs: {
+        default: {
+          "https://some.pod/resource": {
+            predicates: {
+              "http://www.w3.org/1999/02/22-rdf-syntax-ns#type": {
+                namedNodes: [
+                  "http://xmlns.com/foaf/0.1/PersonalProfileDocument",
+                ],
+              },
+              "http://xmlns.com/foaf/0.1/maker": {
+                namedNodes: ["https://some.pod/resource#me"],
+              },
+              "http://xmlns.com/foaf/0.1/primaryTopic": {
+                namedNodes: ["https://some.pod/resource#me"],
+              },
+            },
+            type: "Subject",
+            url: "https://some.pod/resource",
+          },
+          "https://some.pod/resource#me": {
+            predicates: {
+              "http://www.w3.org/1999/02/22-rdf-syntax-ns#type": {
+                namedNodes: ["http://xmlns.com/foaf/0.1/Person"],
+              },
+              "http://www.w3.org/2006/vcard/ns#fn": {
+                literals: {
+                  "http://www.w3.org/2001/XMLSchema#string": ["Vincent"],
+                },
+              },
+              "http://www.w3.org/ns/auth/acl#trustedApp": {
+                blankNodes: [
+                  {
+                    "http://www.w3.org/ns/auth/acl#mode": {
+                      namedNodes: [
+                        "http://www.w3.org/ns/auth/acl#Append",
+                        "http://www.w3.org/ns/auth/acl#Control",
+                        "http://www.w3.org/ns/auth/acl#Read",
+                        "http://www.w3.org/ns/auth/acl#Write",
+                      ],
+                    },
+                    "http://www.w3.org/ns/auth/acl#origin": {
+                      namedNodes: ["http://localhost:3000"],
+                    },
+                  },
+                  {
+                    "http://www.w3.org/ns/auth/acl#mode": {
+                      namedNodes: [
+                        "http://www.w3.org/ns/auth/acl#Append",
+                        "http://www.w3.org/ns/auth/acl#Control",
+                        "http://www.w3.org/ns/auth/acl#Read",
+                        "http://www.w3.org/ns/auth/acl#Write",
+                      ],
+                    },
+                    "http://www.w3.org/ns/auth/acl#origin": {
+                      namedNodes: ["https://penny.vincenttunru.com"],
+                    },
+                  },
+                ],
+              },
+            },
+            type: "Subject",
+            url: "https://some.pod/resource#me",
+          },
+        },
+      },
+      internal_resourceInfo: {
+        contentType: "text/turtle",
+        isRawData: false,
+        linkedResources: {},
+        sourceIri: "https://some.pod/resource",
+      },
+      type: "Dataset",
+    });
+  });
+
+  it("does not attempt to detect chains when there are many Blank Nodes, to avoid performance bottlenecks", async () => {
+    function getChainedBlankNode(iteration: number): string {
+      if (iteration === 1000) {
+        return `<https://some.predicate/${iteration}> "Base case"`;
+      }
+      return `<https://some.predicate/${iteration}> [${getChainedBlankNode(
+        iteration + 1
+      )}]`;
+    }
+    const turtle = `
+      @prefix : <#>.
+      @prefix vcard: <http://www.w3.org/2006/vcard/ns#>.
+
+      :me vcard:fn [${getChainedBlankNode(0)}].
+    `;
+
+    const response = new Response(turtle, {
+      headers: {
+        "Content-Type": "text/turtle",
+      },
+    });
+    jest
+      .spyOn(response, "url", "get")
+      .mockReturnValue("https://some.pod/resource");
+
+    const t0 = performance.now();
+    const solidDataset = await responseToSolidDataset(response);
+    const t1 = performance.now();
+
+    // Parsing a document with over 1000 statements will always be somewhat slow
+    // (hence allowing it to take a second), but if it attempts to detect
+    // chains, it will take on the order of >20 seconds.
+    expect(t1 - t0).toBeLessThan(1000);
+    // Blank Nodes should be listed explicitly, rather than as properties on
+    // https://some.pod/resource#me:
+    expect(Object.keys(solidDataset.graphs.default)).not.toStrictEqual([
+      "https://some.pod/resource#me",
+    ]);
+  });
+
   it("throws a meaningful error when the server returned a 403", async () => {
     const response = new Response("Not allowed", { status: 403 });
     jest

src/resource/solidDataset.ts

@@ -233,11 +233,19 @@ export async function responseToSolidDataset(
           solidDataset = addRdfJsQuadToDataset(solidDataset, quad);
         }
       });
-      parser.onComplete(() => {
+      parser.onComplete(async () => {
+        // If a Resource contains more than this number of Blank Nodes,
+        // we consider the detection of chains (O(n^2), I think) to be too
+        // expensive, and just incorporate them as regular Blank Nodes with
+        // non-deterministic, ad-hoc identifiers into the SolidDataset:
+        const maxBlankNodesToDetectChainsFor = 20;
         // Some Blank Nodes only serve to use a set of Quads as the Object for a
         // single Subject. Those Quads will be added to the SolidDataset when
         // their Subject's Blank Node is encountered in the Object position.
-        const chainBlankNodes = getChainBlankNodes(quadsWithBlankNodes);
+        const chainBlankNodes =
+          quadsWithBlankNodes.length <= maxBlankNodesToDetectChainsFor
+            ? getChainBlankNodes(quadsWithBlankNodes)
+            : [];
         const quadsWithoutChainBlankNodeSubjects = quadsWithBlankNodes.filter(
           (quad) =>
             chainBlankNodes.every(