fix: append query path to path resolved from IPNS name (#3)

If an IPNS name resolves to a CID+path, and the requested URL also
has a path, the resolved path should be the path from the IPNS
record joined with the path from the requested URL, not the other
way round.

Author: achingbrain

packages/verified-fetch/package.json

@@ -90,6 +90,7 @@
     "@helia/json": "^3.0.1",
     "@helia/utils": "^0.0.2",
     "@ipld/car": "^5.3.0",
+    "@libp2p/interface-compliance-tests": "^5.3.2",
     "@libp2p/logger": "^4.0.7",
     "@libp2p/peer-id-factory": "^4.0.7",
     "@sgtpooki/file-type": "^1.0.1",

packages/verified-fetch/src/utils/parse-url-string.ts

@@ -98,15 +98,19 @@ export async function parseUrlString ({ urlString, ipns, logger }: ParseUrlStrin
           resolvedPath = resolveResult?.path
           log.trace('resolved %s to %c', cidOrPeerIdOrDnsLink, cid)
           ipnsCache.set(cidOrPeerIdOrDnsLink, resolveResult, 60 * 1000 * 2)
-        } catch (err) {
+        } catch (err: any) {
           log.error('Could not resolve DnsLink for "%s"', cidOrPeerIdOrDnsLink, err)
-          errors.push(err as Error)
+          errors.push(err)
         }
       }
     }
   }
 
   if (cid == null) {
+    if (errors.length === 1) {
+      throw errors[0]
+    }
+
     throw new AggregateError(errors, `Invalid resource. Cannot determine CID from URL "${urlString}"`)
   }
 
@@ -129,26 +133,37 @@ export async function parseUrlString ({ urlString, ipns, logger }: ParseUrlStrin
     }
   }
 
-  /**
-   * join the path from resolve result & given path.
-   * e.g. /ipns/<peerId>/ that is resolved to /ipfs/<cid>/<path1>, when requested as /ipns/<peerId>/<path2>, should be
-   * resolved to /ipfs/<cid>/<path1>/<path2>
-   */
-  const pathParts = []
+  return {
+    protocol,
+    cid,
+    path: joinPaths(resolvedPath, urlPath),
+    query
+  }
+}
 
-  if (urlPath.length > 0) {
-    pathParts.push(urlPath)
+/**
+ * join the path from resolve result & given path.
+ * e.g. /ipns/<peerId>/ that is resolved to /ipfs/<cid>/<path1>, when requested as /ipns/<peerId>/<path2>, should be
+ * resolved to /ipfs/<cid>/<path1>/<path2>
+ */
+function joinPaths (resolvedPath: string | undefined, urlPath: string): string {
+  let path = ''
+
+  if (resolvedPath != null) {
+    path += resolvedPath
   }
 
-  if (resolvedPath != null && resolvedPath.length > 0) {
-    pathParts.push(resolvedPath)
+  if (urlPath.length > 0) {
+    path = `${path.length > 0 ? `${path}/` : path}${urlPath}`
   }
-  const path = pathParts.join('/')
 
-  return {
-    protocol,
-    cid,
-    path,
-    query
+  // replace duplicate forward slashes
+  path = path.replace(/\/(\/)+/g, '/')
+
+  // strip trailing forward slash if present
+  if (path.startsWith('/')) {
+    path = path.substring(1)
   }
+
+  return path
 }