Refactor GH parser to expose a functional api (#145)

Our GitHub parser is implemented via a `GithubParser` class which builds
the GitHub graph. This is a convenient implementation, but an awkward
API. This commit refactors the module so that it exposes a clean `parse`
function, which ingests the GitHub JSON data and returns as completed
graph.

Test plan:
The unit tests have been re-written to use the new public API. All the
snapshots are unchanged, and flow passes. Additionally, I ran `yarn
start` and verified that the GithubGraphFetcher for the Artifact plugin
is still working.

src/plugins/artifact/editor/GithubGraphFetcher.js

@@ -9,7 +9,7 @@ import type {
   NodePayload as GithubNodePayload,
   EdgePayload as GithubEdgePayload,
 } from "../../github/types";
-import {GithubParser} from "../../github/parser";
+import {parse} from "../../github/parser";
 
 type Props = {
   settings: Settings,
@@ -32,9 +32,7 @@ export class GithubGraphFetcher extends React.Component<Props> {
     const {repoOwner, repoName, githubApiToken} = this.props.settings;
     fetchGithubRepo(repoOwner, repoName, githubApiToken)
       .then((json) => {
-        const parser = new GithubParser(`${repoOwner}/${repoName}`);
-        parser.addData(json);
-        return Promise.resolve(parser.graph);
+        return Promise.resolve(parse(`${repoOwner}/${repoName}`, json));
       })
       .then((graph) => {
         this.props.onCreateGraph(graph);

src/plugins/artifact/editor/adapters/githubPluginAdapter.test.js

@@ -5,7 +5,7 @@ import {shallow} from "enzyme";
 import enzymeToJSON from "enzyme-to-json";
 import stringify from "json-stable-stringify";
 
-import {GithubParser} from "../../../github/parser";
+import {parse} from "../../../github/parser";
 import exampleRepoData from "../../../github/demoData/example-repo.json";
 import adapter from "./githubPluginAdapter";
 
@@ -13,9 +13,7 @@ require("../testUtil").configureEnzyme();
 
 describe("githubPluginAdapter", () => {
   it("operates on the example repo", () => {
-    const parser = new GithubParser("sourcecred/example-repo");
-    parser.addData(exampleRepoData);
-    const graph = parser.graph;
+    const graph = parse("sourcecred/example-repo", exampleRepoData);
 
     const result = graph
       .getNodes()

src/plugins/github/parser.js

@@ -30,7 +30,16 @@ import {PLUGIN_NAME} from "./pluginName";
 import {Graph, edgeID} from "../../core/graph";
 const stringify = require("json-stable-stringify");
 
-export class GithubParser {
+export function parse(
+  repositoryName: string,
+  repositoryJSON: RepositoryJSON
+): Graph<NodePayload, EdgePayload> {
+  const parser = new GithubParser(repositoryName);
+  parser.addData(repositoryJSON);
+  return parser.graph;
+}
+
+class GithubParser {
   repositoryName: string;
   graph: Graph<NodePayload, EdgePayload>;
 

src/plugins/github/parser.test.js

@@ -1,15 +1,15 @@
 // @flow
 
 import {AUTHORS_EDGE_TYPE, CONTAINS_EDGE_TYPE} from "./types";
-
-import {GithubParser} from "./parser";
+import type {NodePayload, EdgePayload} from "./types";
+import {parse} from "./parser";
+import type {RepositoryJSON, PullRequestJSON, IssueJSON} from "./graphql";
+import {Graph} from "../../core/graph";
 import exampleRepoData from "./demoData/example-repo.json";
 
 describe("GithubParser", () => {
   describe("whole repo parsing", () => {
-    const parser = new GithubParser("sourcecred/example-repo");
-    parser.addData(exampleRepoData);
-    const graph = parser.graph;
+    const graph = parse("sourcecred/example-repo", exampleRepoData);
 
     it("parses the entire example-repo as expected", () => {
       expect(graph).toMatchSnapshot();
@@ -66,38 +66,70 @@ describe("GithubParser", () => {
     });
   });
 
+  function getIssue(n: number): IssueJSON {
+    const issues = exampleRepoData.repository.issues.nodes;
+    const selected = issues.filter((x) => x.number === n);
+    if (selected.length !== 1) {
+      throw new Error(`Failure finding issue #${n}`);
+    }
+    return selected[0];
+  }
+  function getPR(n: number): PullRequestJSON {
+    const pulls = exampleRepoData.repository.pullRequests.nodes;
+    const selected = pulls.filter((x) => x.number === n);
+    if (selected.length !== 1) {
+      throw new Error(`Failure finding PR #${n}`);
+    }
+    return selected[0];
+  }
+  type ExampleInput = {
+    issues?: number[],
+    prs?: number[],
+  };
+  function parseExample({
+    issues: issueNums = [],
+    prs: prNums = [],
+  }: ExampleInput): Graph<NodePayload, EdgePayload> {
+    const issues = issueNums.map(getIssue);
+    const pullRequests = prNums.map(getPR);
+    const exampleData: RepositoryJSON = {
+      repository: {
+        id: exampleRepoData.repository.id,
+        issues: {
+          nodes: issues,
+          pageInfo: {
+            hasNextPage: false,
+            endCursor: null,
+          },
+        },
+        pullRequests: {
+          nodes: pullRequests,
+          pageInfo: {
+            hasNextPage: false,
+            endCursor: null,
+          },
+        },
+      },
+    };
+    return parse("sourcecred/example-repo", exampleData);
+  }
+
   describe("issue parsing", () => {
     it("parses a simple issue (https://github.com/sourcecred/example-repo/issues/1)", () => {
-      const issue1 = exampleRepoData.repository.issues.nodes[0];
-      expect(issue1.number).toBe(1);
-      const parser = new GithubParser("sourcecred/example-repo");
-      parser.addIssue(issue1);
-      expect(parser.graph).toMatchSnapshot();
+      expect(parseExample({issues: [1]})).toMatchSnapshot();
     });
 
     it("parses an issue with comments (https://github.com/sourcecred/example-repo/issues/6)", () => {
-      const issue6 = exampleRepoData.repository.issues.nodes[3];
-      expect(issue6.number).toBe(6);
-      const parser = new GithubParser("sourcecred/example-repo");
-      parser.addIssue(issue6);
-      expect(parser.graph).toMatchSnapshot();
+      expect(parseExample({issues: [6]})).toMatchSnapshot();
     });
   });
 
   describe("pull request parsing", () => {
     it("parses a simple pull request (https://github.com/sourcecred/example-repo/pull/3)", () => {
-      const pr3 = exampleRepoData.repository.pullRequests.nodes[0];
-      expect(pr3.number).toBe(3);
-      const parser = new GithubParser("sourcecred/example-repo");
-      parser.addPullRequest(pr3);
-      expect(parser.graph).toMatchSnapshot();
+      expect(parseExample({prs: [3]})).toMatchSnapshot();
     });
     it("parses a pr with review comments (https://github.com/sourcecred/example-repo/pull/3)", () => {
-      const pr5 = exampleRepoData.repository.pullRequests.nodes[1];
-      expect(pr5.number).toBe(5);
-      const parser = new GithubParser("sourcecred/example-repo");
-      parser.addPullRequest(pr5);
-      expect(parser.graph).toMatchSnapshot();
+      expect(parseExample({prs: [5]})).toMatchSnapshot();
     });
   });
 });