Factor out `github.porcelain.asEntity` (#246)

@wchargin suggested that the entity-wrapping logic in porcelain
reference handling should be factored out as its own method. This was a
great suggestion; it will be very useful for plugin consumers, and it
also results in better test coverage.

Test plan: The new unit tests are nice. For your own safety, do not
question or quibble with the magnificent foo plugin.

src/plugins/github/porcelain.js

@@ -48,6 +48,8 @@ import {
   REFERENCES_EDGE_TYPE,
 } from "./types";
 
+import {PLUGIN_NAME} from "./pluginName";
+
 import {COMMIT_NODE_TYPE} from "../git/types";
 
 export type Entity =
@@ -67,6 +69,44 @@ function assertEntityType(e: Entity, t: NodeType) {
   }
 }
 
+export function asEntity(
+  g: Graph<NodePayload, EdgePayload>,
+  addr: Address
+): Entity {
+  const type: NodeType = (addr.type: any);
+  if (addr.pluginName !== PLUGIN_NAME) {
+    throw new Error(
+      `Tried to make GitHub porcelain, but got the wrong plugin name: ${stringify(
+        addr
+      )}`
+    );
+  }
+  switch (type) {
+    case "ISSUE":
+      return new Issue(g, addr);
+    case "PULL_REQUEST":
+      return new PullRequest(g, addr);
+    case "COMMENT":
+      return new Comment(g, addr);
+    case "AUTHOR":
+      return new Author(g, addr);
+    case "PULL_REQUEST_REVIEW":
+      return new PullRequestReview(g, addr);
+    case "PULL_REQUEST_REVIEW_COMMENT":
+      return new PullRequestReviewComment(g, addr);
+    case "REPOSITORY":
+      return new Repository(g, addr);
+    default:
+      // eslint-disable-next-line no-unused-expressions
+      (type: empty);
+      throw new Error(
+        `Tried to make GitHub porcelain, but got invalid type: ${stringify(
+          addr
+        )}`
+      );
+  }
+}
+
 export class Porcelain {
   graph: Graph<NodePayload, EdgePayload>;
 
@@ -190,45 +230,12 @@ class Post<
   }
 
   references(): Entity[] {
-    const result: Entity[] = [];
-    this.graph
+    return this.graph
       .neighborhood(this.nodeAddress, {
         edgeType: REFERENCES_EDGE_TYPE,
         direction: "OUT",
       })
-      .forEach(({neighbor}) => {
-        const type: NodeType = (neighbor.type: any);
-        switch (type) {
-          case "ISSUE":
-            result.push(new Issue(this.graph, neighbor));
-            break;
-          case "PULL_REQUEST":
-            result.push(new PullRequest(this.graph, neighbor));
-            break;
-          case "COMMENT":
-            result.push(new Comment(this.graph, neighbor));
-            break;
-          case "AUTHOR":
-            result.push(new Author(this.graph, neighbor));
-            break;
-          case "PULL_REQUEST_REVIEW":
-            result.push(new PullRequestReview(this.graph, neighbor));
-            break;
-          case "PULL_REQUEST_REVIEW_COMMENT":
-            result.push(new PullRequestReviewComment(this.graph, neighbor));
-            break;
-          case "REPOSITORY":
-            result.push(new Repository(this.graph, neighbor));
-            break;
-          default:
-            // eslint-disable-next-line no-unused-expressions
-            (type: empty);
-            throw new Error(
-              `Attempted to parse reference to unknown entity type ${type}`
-            );
-        }
-      });
-    return result;
+      .map(({neighbor}) => asEntity(this.graph, neighbor));
   }
 }
 

src/plugins/github/porcelain.test.js

@@ -1,8 +1,16 @@
 // @flow
 
+import type {Address} from "../../core/address";
 import {parse} from "./parser";
 import exampleRepoData from "./demoData/example-github.json";
-import {Porcelain, Issue, PullRequest, Comment, Author} from "./porcelain";
+import {
+  asEntity,
+  Porcelain,
+  Issue,
+  PullRequest,
+  Comment,
+  Author,
+} from "./porcelain";
 import {
   AUTHOR_NODE_TYPE,
   COMMENT_NODE_TYPE,
@@ -12,6 +20,8 @@ import {
   PULL_REQUEST_REVIEW_COMMENT_NODE_TYPE,
 } from "./types";
 
+import {PLUGIN_NAME} from "./pluginName";
+
 describe("GitHub porcelain", () => {
   const graph = parse(exampleRepoData);
   const porcelain = new Porcelain(graph);
@@ -23,6 +33,26 @@ describe("GitHub porcelain", () => {
     }
     return result;
   }
+  describe("asEntity", () => {
+    // Note: In the "wrappers" block, we test that the asEntity method works
+    // for each wrapper type. Here, we just test that it fails as expected.
+    it("errors when given an address with the wrong plugin name", () => {
+      const addr: Address = {
+        pluginName: "the magnificent foo plugin",
+        id: "who are you to ask an id of the magnificent foo plugin?",
+        type: "ISSUE",
+      };
+      expect(() => asEntity(graph, addr)).toThrow("wrong plugin name");
+    });
+    it("errors when given an address with a bad node type", () => {
+      const addr: Address = {
+        pluginName: PLUGIN_NAME,
+        id: "if you keep asking for my id you will make me angry",
+        type: "the foo plugin's magnificence extends to many plugins",
+      };
+      expect(() => asEntity(graph, addr)).toThrow("invalid type");
+    });
+  });
   describe("has repository finding", () => {
     it("which works for an existing repository", () => {
       expect(porcelain.repository("sourcecred", "example-github")).toEqual(
@@ -40,6 +70,7 @@ describe("GitHub porcelain", () => {
       expect(repo.url()).toBe("https://github.com/sourcecred/example-github");
       expect(repo.owner()).toBe("sourcecred");
       expect(repo.name()).toBe("example-github");
+      expect(repo).toEqual(asEntity(graph, repo.address()));
     });
     it("Issues", () => {
       const issue = issueOrPRByNumber(1);
@@ -53,6 +84,7 @@ describe("GitHub porcelain", () => {
       expect(issue.node()).toMatchSnapshot();
       expect(issue.address()).toEqual(issue.node().address);
       expect(issue.authors().map((x) => x.login())).toEqual(["decentralion"]);
+      expect(issue).toEqual(asEntity(graph, issue.address()));
     });
     describe("PullRequests", () => {
       it("Merged", () => {
@@ -69,6 +101,7 @@ describe("GitHub porcelain", () => {
         expect(pullRequest.mergeCommitHash()).toEqual(
           "0a223346b4e6dec0127b1e6aa892c4ee0424b66a"
         );
+        expect(pullRequest).toEqual(asEntity(graph, pullRequest.address()));
       });
       it("Unmerged", () => {
         const pullRequest = PullRequest.from(issueOrPRByNumber(9));
@@ -82,6 +115,7 @@ describe("GitHub porcelain", () => {
       expect(reviews).toHaveLength(2);
       expect(reviews[0].state()).toBe("CHANGES_REQUESTED");
       expect(reviews[1].state()).toBe("APPROVED");
+      expect(reviews[0]).toEqual(asEntity(graph, reviews[0].address()));
     });
 
     it("Pull Request Review Comments", () => {
@@ -96,6 +130,7 @@ describe("GitHub porcelain", () => {
       );
       expect(comment.body()).toBe("seems a bit capricious");
       expect(comment.authors().map((a) => a.login())).toEqual(["wchargin"]);
+      expect(comment).toEqual(asEntity(graph, comment.address()));
     });
 
     it("Comments", () => {
@@ -111,6 +146,7 @@ describe("GitHub porcelain", () => {
       expect(comment.node()).toMatchSnapshot();
       expect(comment.address()).toEqual(comment.node().address);
       expect(comment.authors().map((x) => x.login())).toEqual(["decentralion"]);
+      expect(comment).toEqual(asEntity(graph, comment.address()));
     });
 
     it("Authors", () => {
@@ -127,6 +163,7 @@ describe("GitHub porcelain", () => {
       expect(decentralion.subtype()).toBe("USER");
       expect(decentralion.node()).toMatchSnapshot();
       expect(decentralion.address()).toEqual(decentralion.node().address);
+      expect(decentralion).toEqual(asEntity(graph, decentralion.address()));
     });
   });