Backend: implement PluginLoaders.declarations (#1616)

This is the first of several commits to create the PluginLoaders
abstraction. Using this allows us to define "for all plugins"
semantics, while keeping each underlying plugin interface flexible.

src/backend/pluginLoaders.js

@@ -0,0 +1,39 @@
+//@flow
+
+import {type Project} from "../core/project";
+import {type PluginDeclaration} from "../analysis/pluginDeclaration";
+import {type Loader as GithubLoader} from "../plugins/github/loader";
+import {type Loader as IdentityLoader} from "../plugins/identity/loader";
+import {type Loader as DiscourseLoader} from "../plugins/discourse/loader";
+
+/**
+ * A type combining all known plugin Loader interfaces.
+ *
+ * Using this allows us to define "for all plugins" semantics, while keeping
+ * each underlying plugin's interface flexible.
+ */
+export type PluginLoaders = {|
+  +github: GithubLoader,
+  +discourse: DiscourseLoader,
+  +identity: IdentityLoader,
+|};
+
+/**
+ * Gets all relevant PluginDeclarations for a given Project.
+ */
+export function declarations(
+  {github, discourse, identity}: PluginLoaders,
+  project: Project
+): $ReadOnlyArray<PluginDeclaration> {
+  const plugins: PluginDeclaration[] = [];
+  if (project.repoIds.length) {
+    plugins.push(github.declaration());
+  }
+  if (project.discourseServer != null) {
+    plugins.push(discourse.declaration());
+  }
+  if (project.identities.length) {
+    plugins.push(identity.declaration());
+  }
+  return plugins;
+}

src/backend/pluginLoaders.test.js

@@ -0,0 +1,72 @@
+// @flow
+
+import {createProject} from "../core/project";
+import {makeRepoId} from "../plugins/github/repoId";
+import * as PluginLoaders from "./pluginLoaders";
+
+const fakeGithubDec = ("fake-github-dec": any);
+const fakeDiscourseDec = ("fake-discourse-dec": any);
+const fakeIdentityDec = ("fake-identity-dec": any);
+
+const mockPluginLoaders = () => ({
+  github: {
+    declaration: jest.fn().mockReturnValue(fakeGithubDec),
+  },
+  discourse: {
+    declaration: jest.fn().mockReturnValue(fakeDiscourseDec),
+  },
+  identity: {
+    declaration: jest.fn().mockReturnValue(fakeIdentityDec),
+  },
+});
+
+describe("src/backend/pluginLoaders", () => {
+  const exampleRepoId = makeRepoId("sourcecred-test", "example-github");
+
+  describe("declarations", () => {
+    it("should include discourse declaration", async () => {
+      // Given
+      const loaders = mockPluginLoaders();
+      const project = createProject({
+        id: "has-discourse",
+        discourseServer: {serverUrl: "http://foo.bar"},
+      });
+
+      // When
+      const decs = PluginLoaders.declarations(loaders, project);
+
+      // Then
+      expect(decs).toEqual([fakeDiscourseDec]);
+    });
+
+    it("should include github declaration", async () => {
+      // Given
+      const loaders = mockPluginLoaders();
+      const project = createProject({
+        id: "has-github",
+        repoIds: [exampleRepoId],
+      });
+
+      // When
+      const decs = PluginLoaders.declarations(loaders, project);
+
+      // Then
+      expect(decs).toEqual([fakeGithubDec]);
+    });
+
+    it("should include identity declaration", async () => {
+      // Given
+      const loaders = mockPluginLoaders();
+      const project = createProject({
+        id: "has-identity",
+        identities: [{username: "foo", aliases: ["github/foo"]}],
+      });
+
+      // When
+      const decs = PluginLoaders.declarations(loaders, project);
+
+      // Then
+      expect(decs).toEqual([fakeIdentityDec]);
+    });
+  });
+});

src/plugins/discourse/loader.js

@@ -0,0 +1,12 @@
+// @flow
+
+import {type PluginDeclaration} from "../../analysis/pluginDeclaration";
+import {declaration} from "./declaration";
+
+export interface Loader {
+  declaration(): PluginDeclaration;
+}
+
+export default ({
+  declaration: () => declaration,
+}: Loader);

src/plugins/github/loader.js

@@ -0,0 +1,12 @@
+// @flow
+
+import {type PluginDeclaration} from "../../analysis/pluginDeclaration";
+import {declaration} from "./declaration";
+
+export interface Loader {
+  declaration(): PluginDeclaration;
+}
+
+export default ({
+  declaration: () => declaration,
+}: Loader);

src/plugins/identity/loader.js

@@ -0,0 +1,12 @@
+// @flow
+
+import {type PluginDeclaration} from "../../analysis/pluginDeclaration";
+import {declaration} from "./declaration";
+
+export interface Loader {
+  declaration(): PluginDeclaration;
+}
+
+export default ({
+  declaration: () => declaration,
+}: Loader);