Add dispatch methods for plugin adapters (#619)

This commit adds some consistent and tested methods for getting the
appropriate plugin adapter for a given Node/Edge address. There are
methods for both static and dynamic adapters.

In the event that more than one plugin adapter matches the given
address, an error is thrown; likewise in the case where there is no
matching adapter.

Test plan: `yarn test`

Relevant to #465

src/app/credExplorer/PagerankTable.js

@@ -14,23 +14,18 @@ import type {
   ScoredConnection,
 } from "../../core/attribution/pagerankNodeDecomposition";
 import type {Connection} from "../../core/attribution/graphToMarkovChain";
-import type {DynamicPluginAdapter} from "../pluginAdapter";
+import {
+  type DynamicPluginAdapter,
+  dynamicDispatchByNode,
+  dynamicDispatchByEdge,
+} from "../pluginAdapter";
 import * as NullUtil from "../../util/null";
 
-// TODO: Factor this out and test it (#465)
 export function nodeDescription(
   address: NodeAddressT,
   adapters: $ReadOnlyArray<DynamicPluginAdapter>
 ): string {
-  const adapter = adapters.find((adapter) =>
-    NodeAddress.hasPrefix(address, adapter.static().nodePrefix())
-  );
-  if (adapter == null) {
-    const result = NodeAddress.toString(address);
-    console.warn(`No adapter for ${result}`);
-    return result;
-  }
-
+  const adapter = dynamicDispatchByNode(adapters, address);
   try {
     return adapter.nodeDescription(address);
   } catch (e) {
@@ -45,14 +40,7 @@ function edgeVerb(
   direction: "FORWARD" | "BACKWARD",
   adapters: $ReadOnlyArray<DynamicPluginAdapter>
 ): string {
-  const adapter = adapters.find((adapter) =>
-    EdgeAddress.hasPrefix(address, adapter.static().edgePrefix())
-  );
-  if (adapter == null) {
-    const result = EdgeAddress.toString(address);
-    console.warn(`No adapter for ${result}`);
-    return result;
-  }
+  const adapter = dynamicDispatchByEdge(adapters, address);
 
   const edgeType = adapter
     .static()

src/app/pluginAdapter.js

@@ -1,6 +1,12 @@
 // @flow
 
-import type {Graph, NodeAddressT, EdgeAddressT} from "../core/graph";
+import {
+  Graph,
+  NodeAddress,
+  EdgeAddress,
+  type NodeAddressT,
+  type EdgeAddressT,
+} from "../core/graph";
 import type {Repo} from "../core/repo";
 
 export type EdgeType = {|
@@ -29,3 +35,53 @@ export interface DynamicPluginAdapter {
   nodeDescription(NodeAddressT): string;
   static (): StaticPluginAdapter;
 }
+
+function findUniqueMatch<T>(
+  xs: $ReadOnlyArray<T>,
+  predicate: (T) => boolean
+): T {
+  const results = xs.filter(predicate);
+  if (results.length > 1) {
+    throw new Error("Multiple entities match predicate");
+  }
+  if (results.length === 0) {
+    throw new Error("No entity matches predicate");
+  }
+  return results[0];
+}
+
+export function staticDispatchByNode(
+  adapters: $ReadOnlyArray<StaticPluginAdapter>,
+  x: NodeAddressT
+): StaticPluginAdapter {
+  return findUniqueMatch(adapters, (a) =>
+    NodeAddress.hasPrefix(x, a.nodePrefix())
+  );
+}
+
+export function staticDispatchByEdge(
+  adapters: $ReadOnlyArray<StaticPluginAdapter>,
+  x: EdgeAddressT
+): StaticPluginAdapter {
+  return findUniqueMatch(adapters, (a) =>
+    EdgeAddress.hasPrefix(x, a.edgePrefix())
+  );
+}
+
+export function dynamicDispatchByNode(
+  adapters: $ReadOnlyArray<DynamicPluginAdapter>,
+  x: NodeAddressT
+): DynamicPluginAdapter {
+  return findUniqueMatch(adapters, (a) =>
+    NodeAddress.hasPrefix(x, a.static().nodePrefix())
+  );
+}
+
+export function dynamicDispatchByEdge(
+  adapters: $ReadOnlyArray<DynamicPluginAdapter>,
+  x: EdgeAddressT
+): DynamicPluginAdapter {
+  return findUniqueMatch(adapters, (a) =>
+    EdgeAddress.hasPrefix(x, a.static().edgePrefix())
+  );
+}

src/app/pluginAdapter.test.js

@@ -0,0 +1,101 @@
+// @flow
+
+import {
+  Graph,
+  NodeAddress,
+  EdgeAddress,
+  type NodeAddressT,
+} from "../core/graph";
+import {
+  type StaticPluginAdapter,
+  type DynamicPluginAdapter,
+  staticDispatchByNode,
+  staticDispatchByEdge,
+  dynamicDispatchByNode,
+  dynamicDispatchByEdge,
+} from "./pluginAdapter";
+
+describe("app/pluginAdapter", () => {
+  function example() {
+    const staticFooAdapter: StaticPluginAdapter = {
+      name: () => "foo",
+      nodePrefix: () => NodeAddress.fromParts(["foo"]),
+      edgePrefix: () => EdgeAddress.fromParts(["foo"]),
+      nodeTypes: () => [],
+      edgeTypes: () => [],
+      load: (_unused_repo) => Promise.resolve(dynamicFooAdapter),
+    };
+    const dynamicFooAdapter: DynamicPluginAdapter = {
+      graph: () => new Graph(),
+      nodeDescription: (x: NodeAddressT) => NodeAddress.toString(x),
+      static: () => staticFooAdapter,
+    };
+    const staticBarAdapter: StaticPluginAdapter = {
+      name: () => "bar",
+      nodePrefix: () => NodeAddress.fromParts(["bar"]),
+      edgePrefix: () => EdgeAddress.fromParts(["bar"]),
+      nodeTypes: () => [],
+      edgeTypes: () => [],
+      load: (_unused_repo) => Promise.resolve(dynamicBarAdapter),
+    };
+    const dynamicBarAdapter: DynamicPluginAdapter = {
+      graph: () => new Graph(),
+      nodeDescription: (x) => NodeAddress.toString(x),
+      static: () => staticBarAdapter,
+    };
+    const statics = [staticFooAdapter, staticBarAdapter];
+    const dynamics = [dynamicFooAdapter, dynamicBarAdapter];
+    return {
+      statics,
+      dynamics,
+      staticFooAdapter,
+      dynamicFooAdapter,
+    };
+  }
+
+  describe("dispatching", () => {
+    describe("error handling", () => {
+      // Just testing staticDispatchByNode is fine, as they all call the same
+      // implementation
+      it("errors if it cannot match", () => {
+        const {statics} = example();
+        const zod = NodeAddress.fromParts(["zod"]);
+        expect(() => staticDispatchByNode(statics, zod)).toThrowError(
+          "No entity matches"
+        );
+      });
+      it("errors if there are multiple matches", () => {
+        const {staticFooAdapter} = example();
+        const statics = [staticFooAdapter, staticFooAdapter];
+        const foo = NodeAddress.fromParts(["foo"]);
+        expect(() => staticDispatchByNode(statics, foo)).toThrowError(
+          "Multiple entities match"
+        );
+      });
+    });
+    it("staticDispatchByNode works", () => {
+      const {statics, staticFooAdapter} = example();
+      const fooSubnode = NodeAddress.fromParts(["foo", "sub"]);
+      expect(staticDispatchByNode(statics, fooSubnode)).toBe(staticFooAdapter);
+    });
+    it("staticDispatchByEdge works", () => {
+      const {statics, staticFooAdapter} = example();
+      const fooSubedge = EdgeAddress.fromParts(["foo", "sub"]);
+      expect(staticDispatchByEdge(statics, fooSubedge)).toBe(staticFooAdapter);
+    });
+    it("dynamicDispatchByNode works", () => {
+      const {dynamics, dynamicFooAdapter} = example();
+      const fooSubnode = NodeAddress.fromParts(["foo", "sub"]);
+      expect(dynamicDispatchByNode(dynamics, fooSubnode)).toBe(
+        dynamicFooAdapter
+      );
+    });
+    it("dynamicDispatchByEdge works", () => {
+      const {dynamics, dynamicFooAdapter} = example();
+      const fooSubedge = EdgeAddress.fromParts(["foo", "sub"]);
+      expect(dynamicDispatchByEdge(dynamics, fooSubedge)).toBe(
+        dynamicFooAdapter
+      );
+    });
+  });
+});