GitHub: Mint cred only for merged PRs (#1933)

This commit modifies the GitHub createGraph method so that it now
returns a WeightedGraph, and that WeightedGraph sets weight 0 for any
pull request which hasn't been merged.

This improves Cred robustness, since it's easy to (non-maliciously)
create a bunch of unmerged PRs, but getting them merged is a signal of
quality.

Test plan: Unit tests added.

src/plugins/github/__snapshots__/createGraph.test.js.snap

@@ -3320,3 +3320,12 @@ Array [
   },
 ]
 `;
+
+exports[`plugins/github/createGraph example weights matches snapshot 1`] = `
+Object {
+  "edgeWeights": Map {},
+  "nodeWeights": Map {
+    "NsourcecredgithubPULLsourcecred-testexample-github9" => 0,
+  },
+}
+`;

src/plugins/github/cliPlugin.js

@@ -9,8 +9,11 @@ import type {CacheProvider} from "../../backend/cache";
 import type {CliPlugin, PluginDirectoryContext} from "../../cli/cliPlugin";
 import type {PluginDeclaration} from "../../analysis/pluginDeclaration";
 import type {ReferenceDetector} from "../../core/references/referenceDetector";
-import type {WeightedGraph} from "../../core/weightedGraph";
+import {
-import {Graph} from "../../core/graph";
+  type WeightedGraph,
+  merge as mergeWeightedGraph,
+} from "../../core/weightedGraph";
+import {merge as mergeWeights} from "../../core/weights";
 import {RelationalView} from "./relationalView";
 import {createGraph} from "./createGraph";
 import {declaration} from "./declaration";
@@ -87,15 +90,16 @@ export class GithubCliPlugin implements CliPlugin {
     for (const repoId of config.repoIds) {
       repositories.push(await fetchGithubRepoFromCache(repoId, {token, cache}));
     }
-    const graph = Graph.merge(
+    const wg = mergeWeightedGraph(
       repositories.map((r) => {
         const rv = new RelationalView();
         rv.addRepository(r);
         return createGraph(rv);
       })
     );
-    const weights = weightsForDeclaration(declaration);
+    const pluginDefaultWeights = weightsForDeclaration(declaration);
-    return {graph, weights};
+    const weights = mergeWeights([wg.weights, pluginDefaultWeights]);
+    return {graph: wg.graph, weights};
   }
 
   async referenceDetector(

src/plugins/github/createGraph.js

@@ -2,23 +2,27 @@
 
 import * as NullUtil from "../../util/null";
 import {Graph} from "../../core/graph";
+import {type WeightedGraph} from "../../core/weightedGraph";
+import {type Weights, empty as emptyWeights} from "../../core/weights";
 import * as GitNode from "../git/nodes";
 import * as N from "./nodes";
 import * as R from "./relationalView";
 import {createEdge} from "./edges";
 import {ReactionContent$Values as Reactions} from "./graphqlTypes";
 
-export function createGraph(view: R.RelationalView): Graph {
+export function createGraph(view: R.RelationalView): WeightedGraph {
   const creator = new GraphCreator();
   creator.addData(view);
-  return creator.graph;
+  return {graph: creator.graph, weights: creator.weights};
 }
 
 class GraphCreator {
   graph: Graph;
+  weights: Weights;
 
   constructor() {
     this.graph = new Graph();
+    this.weights = emptyWeights();
   }
 
   addData(view: R.RelationalView) {
@@ -46,6 +50,10 @@ class GraphCreator {
         this.graph.addEdge(
           createEdge.mergedAs(pull.address(), commit, commitTimestamp)
         );
+      } else {
+        const addr = N.toRaw(pull.address());
+        // Un-merged PRs do not mint cred.
+        this.weights.nodeWeights.set(addr, 0);
       }
     }
 

src/plugins/github/createGraph.test.js

@@ -1,9 +1,34 @@
 // @flow
 
-import {exampleGraph} from "./example/example";
+import {exampleGraph, exampleRelationalView} from "./example/example";
+import {empty as emptyWeights} from "../../core/weights";
+import {createGraph} from "./createGraph";
+import * as N from "./nodes";
 
 describe("plugins/github/createGraph", () => {
   it("example graph matches snapshot", () => {
-    expect(exampleGraph()).toMatchSnapshot();
+    expect(exampleGraph().graph).toMatchSnapshot();
+  });
+  it("example weights matches snapshot", () => {
+    expect(exampleGraph().weights).toMatchSnapshot();
+  });
+  it("sets weight to 0 for un-merged PRs", () => {
+    const view = exampleRelationalView();
+    const unmergedPrs = Array.from(view.pulls()).filter(
+      (x) => x.mergedAs() == null
+    );
+    const mergedPrs = Array.from(view.pulls()).filter(
+      (x) => x.mergedAs() != null
+    );
+    expect(unmergedPrs).not.toHaveLength(0);
+    expect(mergedPrs).not.toHaveLength(0);
+
+    const expectedWeights = emptyWeights();
+    for (const unmerged of unmergedPrs) {
+      const addr = N.toRaw(unmerged.address());
+      expectedWeights.nodeWeights.set(addr, 0);
+    }
+    const {weights} = createGraph(view);
+    expect(weights).toEqual(expectedWeights);
   });
 });

src/plugins/github/example/example.js

@@ -2,7 +2,7 @@
 
 import {RelationalView} from "../relationalView";
 import type {Repository} from "../graphqlTypes";
-import {Graph} from "../../../core/graph";
+import {type WeightedGraph} from "../../../core/weightedGraph";
 import cloneDeep from "lodash.clonedeep";
 import {createGraph} from "../createGraph";
 
@@ -16,7 +16,7 @@ export function exampleRelationalView(): RelationalView {
   return rv;
 }
 
-export function exampleGraph(): Graph {
+export function exampleGraph(): WeightedGraph {
   return createGraph(exampleRelationalView());
 }