Add getNextVersionFromTags

Summary:
Changelog: [Internal] - Add getNextVersionFromTags to determine next release version off a release branch

In more detail - this work is part of an effort to automate the release process by using a push to a release branch as a trigger to prepare, package and deploy react-native to npm from CircleCI

This function is later used in `prepare-package-for-release` script in D32556610 to bump the version

Reviewed By: cortinico, ShikaSD

Differential Revision: D32556609

fbshipit-source-id: 7d93ead0b34318a58ffeb876715fbd34d6041f4e

Author: Luna Wei

scripts/__tests__/version-utils-test.js

@@ -7,9 +7,37 @@
  * @format
  */
 
-const {parseVersion} = require('../version-utils');
+const {parseVersion, getNextVersionFromTags} = require('../version-utils');
+
+let execResult = null;
+jest.mock('shelljs', () => ({
+  exec: () => {
+    return {
+      stdout: execResult,
+    };
+  },
+}));
 
 describe('version-utils', () => {
+  describe('getNextVersionFromTags', () => {
+    it('should increment last stable tag', () => {
+      execResult =
+        'v0.66.3\nv0.66.2\nv0.66.1\nv0.66.0-rc.4\nv0.66.0-rc.3\nv0.66.0-rc.2\nv0.66.0-rc.1\nv0.66.0-rc.0';
+      expect(getNextVersionFromTags('0.66-stable')).toBe('0.66.4');
+    });
+
+    it('should find last prerelease tag and increment', () => {
+      execResult =
+        'v0.66.0-rc.4\nv0.66.0-rc.3\nv0.66.0-rc.2\nv0.66.0-rc.1\nv0.66.0-rc.0';
+      expect(getNextVersionFromTags('0.66-stable')).toBe('0.66.0-rc.5');
+    });
+
+    it('should return rc.0 version if no previous tags', () => {
+      execResult = '\n';
+      expect(getNextVersionFromTags('0.66-stable')).toBe('0.66.0-rc.0');
+    });
+  });
+
   describe('parseVersion', () => {
     it('should throw error if invalid match', () => {
       function testInvalidVersion() {

scripts/version-utils.js

@@ -7,6 +7,8 @@
  * @format
  */
 
+const {exec} = require('shelljs');
+
 function parseVersion(versionStr) {
   const match = versionStr.match(/^v?((\d+)\.(\d+)\.(\d+)(?:-(.+))?)$/);
   if (!match) {
@@ -24,6 +26,49 @@ function parseVersion(versionStr) {
   };
 }
 
+function getLatestVersionTag(branchVersion) {
+  // Returns list of tags like ["v0.67.2", "v0.67.1", "v0.67.0-rc.3", "v0.67.0-rc.2", ...] in reverse lexical order
+  const tags = exec(`git tag --list "v${branchVersion}*" --sort=-refname`, {
+    silent: true,
+  })
+    .stdout.trim()
+    .split('\n')
+    .filter(tag => tag.length > 0);
+
+  // If there are no tags, return null
+  if (tags.length === 0) {
+    return null;
+  }
+
+  // Return most recent tag (with the "v" prefix)
+  return tags[0];
+}
+
+function getNextVersionFromTags(branch) {
+  // Assumption that branch names will follow pattern `{major}.{minor}-stable`
+  // Ex. "0.67-stable" -> "0.67"
+  const branchVersion = branch.replace('-stable', '');
+
+  // Get the latest version tag of the release branch
+  const versionTag = getLatestVersionTag(branchVersion);
+
+  // If there are no tags , we assume this is the first pre-release
+  if (versionTag == null) {
+    return `${branchVersion}.0-rc.0`;
+  }
+
+  const {major, minor, patch, prerelease} = parseVersion(versionTag);
+  if (prerelease != null) {
+    // prelease is of the form "rc.X"
+    const prereleasePatch = parseInt(prerelease.slice(3), 10);
+    return `${major}.${minor}.${patch}-rc.${prereleasePatch + 1}`;
+  }
+
+  // If not prerelease, increment the patch version
+  return `${major}.${minor}.${parseInt(patch, 10) + 1}`;
+}
+
 module.exports = {
   parseVersion,
+  getNextVersionFromTags,
 };