enhancement: Update string renderer to add empty lines only when commits are present.

src/functional/__snapshots__/markdown-empty.spec.ts.snap

@@ -0,0 +1,7 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`createMarkdown single project outputs correct changelog 1`] = `""`;
+
+exports[`createMarkdown single tags outputs correct changelog 1`] = `""`;
+
+exports[`multiple tags outputs correct changelog 1`] = `""`;

src/functional/markdown-empty.spec.ts

@@ -0,0 +1,177 @@
+/* tslint:disable:max-line-length */
+
+import { CommitListItem } from "../git";
+
+jest.mock("../../src/progress-bar");
+jest.mock("../../src/changelog");
+jest.mock("../../src/github-api");
+jest.mock("../git");
+jest.mock("../fetch");
+
+const listOfCommits: CommitListItem[] = [];
+
+const listOfTags = ["v6.0.0", "v5.0.0", "v4.0.0", "v3.0.0", "v2.0.0", "v1.0.0", "v0.1.0"];
+
+const listOfPackagesForEachCommit: { [id: string]: string[] } = {
+  a0000001: ["packages/random/foo.js"],
+  a0000002: ["packages/random/package.json"],
+  a0000003: ["packages/a-new-hope/rebels.js"],
+  a0000004: ["packages/a-new-hope/package.json"],
+  a0000005: ["packages/empire-strikes-back/death-star.js"],
+  a0000006: ["packages/empire-strikes-back/death-star.js"],
+  a0000007: ["packages/empire-strikes-back/hoth.js"],
+  a0000008: ["packages/empire-strikes-back/hoth.js"],
+  a0000009: ["packages/empire-strikes-back/package.json"],
+  a0000010: ["packages/return-of-the-jedi/jabba-the-hutt.js"],
+  a0000011: ["packages/return-of-the-jedi/vader-luke.js"],
+  a0000012: ["packages/return-of-the-jedi/leia.js"],
+  a0000013: ["packages/return-of-the-jedi/package.json"],
+  a0000014: ["packages/the-force-awakens/mission.js", "packages/rogue-one/mission.js"],
+  a0000015: ["packages/untitled/script.md"],
+};
+
+const listOfFileForEachCommit: { [id: string]: string[] } = {
+  a0000001: ["random/foo.js"],
+  a0000002: ["random/package.json"],
+  a0000003: ["a-new-hope/rebels.js"],
+  a0000004: ["a-new-hope/package.json"],
+  a0000005: ["empire-strikes-back/death-star.js"],
+  a0000006: ["empire-strikes-back/death-star.js"],
+  a0000007: ["empire-strikes-back/hoth.js"],
+  a0000008: ["empire-strikes-back/hoth.js"],
+  a0000009: ["empire-strikes-back/package.json"],
+  a0000010: ["return-of-the-jedi/jabba-the-hutt.js"],
+  a0000011: ["return-of-the-jedi/vader-luke.js"],
+  a0000012: ["return-of-the-jedi/leia.js"],
+  a0000013: ["return-of-the-jedi/package.json"],
+  a0000014: ["the-force-awakens/mission.js", "rogue-one/mission.js"],
+  a0000015: ["untitled/script.md"],
+};
+
+const usersCache = {
+  "https://api.github.com/users/luke": {
+    login: "luke",
+    html_url: "https://github.com/luke",
+    name: "Luke Skywalker",
+  },
+  "https://api.github.com/users/vader": {
+    login: "vader",
+    html_url: "https://github.com/vader",
+    name: "Darth Vader",
+  },
+  "https://api.github.com/users/gtarkin": {
+    login: "gtarkin",
+    html_url: "https://github.com/gtarkin",
+    name: "Governor Tarkin",
+  },
+};
+const issuesCache = {
+  "https://api.github.com/repos/lerna/lerna-changelog/issues/1": {
+    number: 1,
+    title: "feat: May the force be with you",
+    labels: [{ name: "Type: New Feature" }],
+    pull_request: {
+      html_url: "https://github.com/lerna/lerna-changelog/pull/1",
+    },
+    user: usersCache["https://api.github.com/users/luke"],
+  },
+  "https://api.github.com/repos/lerna/lerna-changelog/issues/2": {
+    number: 2,
+    title: "chore: Terminate her... immediately!",
+    labels: [{ name: "Type: Breaking Change" }],
+    pull_request: {
+      html_url: "https://github.com/lerna/lerna-changelog/pull/2",
+    },
+    user: usersCache["https://api.github.com/users/gtarkin"],
+  },
+  "https://api.github.com/repos/lerna/lerna-changelog/issues/3": {
+    number: 3,
+    title: "fix: Get me the rebels base!",
+    labels: [{ name: "Type: Bug" }],
+    pull_request: {
+      html_url: "https://github.com/lerna/lerna-changelog/pull/3",
+    },
+    user: usersCache["https://api.github.com/users/vader"],
+  },
+};
+
+describe("multiple tags", () => {
+  it("outputs correct changelog", async () => {
+    require("../git").changedPaths.mockImplementation((sha: string) => listOfPackagesForEachCommit[sha]);
+    require("../git").lastTag.mockImplementation(() => "v8.0.0");
+    require("../git").listCommits.mockImplementation(() => listOfCommits);
+    require("../git").listTagNames.mockImplementation(() => [
+      "a-new-hope@4.0.0",
+      "attack-of-the-clones@3.1.0",
+      "empire-strikes-back@5.0.0",
+      "return-of-the-jedi@6.0.0",
+      "revenge-of-the-sith@3.0.0",
+      "the-force-awakens@7.0.0",
+      "the-phantom-menace@1.0.0",
+    ]);
+
+    require("../fetch").__setMockResponses({
+      ...usersCache,
+      ...issuesCache,
+    });
+
+    const MockedChangelog = require("../changelog").default;
+    const changelog = new MockedChangelog();
+
+    const markdown = await changelog.createMarkdown();
+
+    expect(markdown).toMatchSnapshot();
+  });
+});
+
+describe("createMarkdown", () => {
+  beforeEach(() => {
+    require("../fetch").__resetMockResponses();
+  });
+
+  afterEach(() => {
+    jest.resetAllMocks();
+  });
+
+  describe("single tags", () => {
+    it("outputs correct changelog", async () => {
+      require("../git").changedPaths.mockImplementation((sha: string) => listOfPackagesForEachCommit[sha]);
+      require("../git").lastTag.mockImplementation(() => "v8.0.0");
+      require("../git").listCommits.mockImplementation(() => listOfCommits);
+      require("../git").listTagNames.mockImplementation(() => listOfTags);
+
+      require("../fetch").__setMockResponses({
+        ...usersCache,
+        ...issuesCache,
+      });
+
+      const MockedChangelog = require("../changelog").default;
+      const changelog = new MockedChangelog();
+
+      const markdown = await changelog.createMarkdown();
+
+      expect(markdown).toMatchSnapshot();
+    });
+  });
+
+  describe("single project", () => {
+    it("outputs correct changelog", async () => {
+      require("../git").changedPaths.mockImplementation((sha: string) => listOfFileForEachCommit[sha]);
+      require("../git").lastTag.mockImplementation(() => "v8.0.0");
+      require("../git").listCommits.mockImplementation(() => listOfCommits);
+      require("../git").listTagNames.mockImplementation(() => listOfTags);
+
+      require("../fetch").__setMockResponses({
+        ...usersCache,
+        ...issuesCache,
+      });
+
+      const MockedChangelog = require("../changelog").default;
+      const changelog = new MockedChangelog();
+
+      const markdown = await changelog.createMarkdown();
+
+      expect(markdown).toMatchSnapshot();
+    });
+  });
+});

src/markdown-renderer.ts

@@ -23,10 +23,11 @@ export default class MarkdownRenderer {
   }
 
   public renderMarkdown(releases: Release[]) {
-    return `\n${releases
+    let output = releases
       .map(release => this.renderRelease(release))
       .filter(Boolean)
-      .join("\n\n\n")}`;
+      .join("\n\n\n");
+    return output ? `\n${output}` : "";
   }
 
   public renderRelease(release: Release): string | undefined {