do not add parents to simple paths (#2502)

pipeline/relation_embedder/path_concatenator/src/main/scala/weco/pipeline/path_concatenator/PathOps.scala

@@ -11,6 +11,9 @@ object PathOps {
 
     lazy val isCircular: Boolean =
       path.indexOf("/") != -1 && firstNode == lastNode
+
+    lazy val isSimple: Boolean =
+      path.indexOf("/") == -1
   }
   def concatenatePaths(parentPath: String, childPath: String): String = {
     val childRoot = childPath.firstNode

pipeline/relation_embedder/path_concatenator/src/main/scala/weco/pipeline/path_concatenator/PathsService.scala

@@ -26,7 +26,7 @@ class PathsService(elasticClient: ElasticClient, index: Index)(
   import PathOps._
 
   def getParentPath(path: String): Future[Option[String]] = {
-    if (path.isCircular) {
+    if (path.isCircular || path.isSimple) {
       Future(None)
     } else {
       val request: SearchRequest = requestBuilder.parentPath(path)

pipeline/relation_embedder/path_concatenator/src/test/scala/weco/pipeline/path_concatenator/PathsServiceTest.scala

@@ -12,9 +12,8 @@ import weco.akka.fixtures.Akka
 import weco.catalogue.internal_model.work.generators.WorkGenerators
 import scala.concurrent.ExecutionContext.Implicits.global
 
-/**
-  * Tests covering the PathsService, which fetches data from Elasticsearch
-  * in order to support the PathConcatenator.
+/** Tests covering the PathsService, which fetches data from Elasticsearch in
+  * order to support the PathConcatenator.
   *
   * These tests require a running ElasticSearch Instance.
   */
@@ -33,7 +32,7 @@ class PathsServiceTest
   private def service(index: Index) =
     new PathsService(
       elasticClient = elasticClient,
-      index = index,
+      index = index
     )
 
   describe("The PathService parentPath getter") {
@@ -43,11 +42,12 @@ class PathsServiceTest
         work(path = "grandparent/parent"),
         work(path = "parent/child")
       )
-      withLocalMergedWorksIndex { index =>
-        insertIntoElasticsearch(index, works: _*)
-        whenReady(service(index).getParentPath("parent/child")) {
-          _ shouldBe Some("grandparent/parent")
-        }
+      withLocalMergedWorksIndex {
+        index =>
+          insertIntoElasticsearch(index, works: _*)
+          whenReady(service(index).getParentPath("parent/child")) {
+            _ shouldBe Some("grandparent/parent")
+          }
       }
     }
 
@@ -60,11 +60,12 @@ class PathsServiceTest
         work(path = "grandparent/parent/brother"),
         work(path = "parent/sister")
       )
-      withLocalMergedWorksIndex { index =>
-        insertIntoElasticsearch(index, works: _*)
-        whenReady(service(index).getParentPath("parent/sister")) {
-          _ shouldBe Some("grandparent/parent")
-        }
+      withLocalMergedWorksIndex {
+        index =>
+          insertIntoElasticsearch(index, works: _*)
+          whenReady(service(index).getParentPath("parent/sister")) {
+            _ shouldBe Some("grandparent/parent")
+          }
       }
     }
 
@@ -77,11 +78,12 @@ class PathsServiceTest
         work(path = "parent"),
         work(path = "parent/child")
       )
-      withLocalMergedWorksIndex { index =>
-        insertIntoElasticsearch(index, works: _*)
-        whenReady(service(index).getParentPath("parent/child")) {
-          _ shouldBe empty
-        }
+      withLocalMergedWorksIndex {
+        index =>
+          insertIntoElasticsearch(index, works: _*)
+          whenReady(service(index).getParentPath("parent/child")) {
+            _ shouldBe empty
+          }
       }
     }
 
@@ -90,11 +92,30 @@ class PathsServiceTest
         work(path = "a/b/c/d/e"),
         work(path = "e/f/g/h/i")
       )
-      withLocalMergedWorksIndex { index =>
-        insertIntoElasticsearch(index, works: _*)
-        whenReady(service(index).getParentPath("e/f/g/h/i")) {
-          _ shouldBe Some("a/b/c/d/e")
-        }
+      withLocalMergedWorksIndex {
+        index =>
+          insertIntoElasticsearch(index, works: _*)
+          whenReady(service(index).getParentPath("e/f/g/h/i")) {
+            _ shouldBe Some("a/b/c/d/e")
+          }
+      }
+    }
+
+    it("does not add a parent to a root-only path") {
+      // When the requested path consists of a single node, it is the root of its own tree,
+      // and cannot have a parent.
+      // An earlier iteration of this service would get confused by the trailing slash in
+      // a path in a different tree.
+      val works: List[Work[Merged]] = List(
+        work(path = "parent"),
+        work(path = "a/completely/different/tree/")
+      )
+      withLocalMergedWorksIndex {
+        index =>
+          insertIntoElasticsearch(index, works: _*)
+          whenReady(service(index).getParentPath("parent")) {
+            _ shouldBe empty
+          }
       }
     }
 
@@ -104,14 +125,15 @@ class PathsServiceTest
         work(path = "grandfather/parent"),
         work(path = "parent/child")
       )
-      withLocalMergedWorksIndex { index =>
-        insertIntoElasticsearch(index, works: _*)
+      withLocalMergedWorksIndex {
+        index =>
+          insertIntoElasticsearch(index, works: _*)
 
-        val future = service(index).getParentPath("parent/child")
+          val future = service(index).getParentPath("parent/child")
 
-        whenReady(future.failed) {
-          _ shouldBe a[RuntimeException]
-        }
+          whenReady(future.failed) {
+            _ shouldBe a[RuntimeException]
+          }
       }
     }
   }
@@ -124,11 +146,12 @@ class PathsServiceTest
         expectedWork,
         work(path = "parent/child/grandchild")
       )
-      withLocalMergedWorksIndex { index =>
-        insertIntoElasticsearch(index, works: _*)
-        whenReady(service(index).getWorkWithPath("parent/child")) {
-          _ shouldBe expectedWork
-        }
+      withLocalMergedWorksIndex {
+        index =>
+          insertIntoElasticsearch(index, works: _*)
+          whenReady(service(index).getWorkWithPath("parent/child")) {
+            _ shouldBe expectedWork
+          }
       }
     }
 
@@ -137,27 +160,29 @@ class PathsServiceTest
         work(path = "parent/child"),
         work(path = "parent/child")
       )
-      withLocalMergedWorksIndex { index =>
-        insertIntoElasticsearch(index, works: _*)
-
-        service(index)
-          .getWorkWithPath("parent/child")
-          .failed
-          .futureValue shouldBe a[RuntimeException]
+      withLocalMergedWorksIndex {
+        index =>
+          insertIntoElasticsearch(index, works: _*)
+
+          service(index)
+            .getWorkWithPath("parent/child")
+            .failed
+            .futureValue shouldBe a[RuntimeException]
       }
     }
 
     it("throws an exception if no work can be found") {
       val works: List[Work[Merged]] = List(
         work(path = "hello/world")
       )
-      withLocalMergedWorksIndex { index =>
-        insertIntoElasticsearch(index, works: _*)
-
-        service(index)
-          .getWorkWithPath("parent/child")
-          .failed
-          .futureValue shouldBe a[RuntimeException]
+      withLocalMergedWorksIndex {
+        index =>
+          insertIntoElasticsearch(index, works: _*)
+
+          service(index)
+            .getWorkWithPath("parent/child")
+            .failed
+            .futureValue shouldBe a[RuntimeException]
       }
     }
   }
@@ -169,26 +194,32 @@ class PathsServiceTest
         work(path = "grandparent/parent"),
         work(path = "parent/child/grandchild1"),
         work(path = "parent/child/grandchild2"),
-        work(path = "grandparent/parent/child/grandchild3"), // ignored - it has already been resolved up to grandparent
-        work(path = "child/grandchild3") // ignored - could be child of a different parent
+        work(path =
+          "grandparent/parent/child/grandchild3"
+        ), // ignored - it has already been resolved up to grandparent
+        work(path =
+          "child/grandchild3"
+        ) // ignored - could be child of a different parent
       )
-      withLocalMergedWorksIndex { index =>
-        insertIntoElasticsearch(index, works: _*)
-        whenReady(service(index).getChildWorks("grandparent/parent")) {
-          _ should contain theSameElementsAs List(works(2), works(3))
-        }
+      withLocalMergedWorksIndex {
+        index =>
+          insertIntoElasticsearch(index, works: _*)
+          whenReady(service(index).getChildWorks("grandparent/parent")) {
+            _ should contain theSameElementsAs List(works(2), works(3))
+          }
       }
     }
     it("Returns an empty list if there are no children") {
       val works: List[Work[Merged]] = List(
         work(path = "grandparent"),
         work(path = "grandparent/parent")
       )
-      withLocalMergedWorksIndex { index =>
-        insertIntoElasticsearch(index, works: _*)
-        whenReady(service(index).getChildWorks("grandparent/parent")) {
-          _ shouldBe empty
-        }
+      withLocalMergedWorksIndex {
+        index =>
+          insertIntoElasticsearch(index, works: _*)
+          whenReady(service(index).getChildWorks("grandparent/parent")) {
+            _ shouldBe empty
+          }
       }
     }
   }