Allow setting merge method through labels

README.md

@@ -96,6 +96,14 @@ The following merge options are supported:
  or [`squash`](https://help.github.com/en/articles/about-pull-request-merges#squash-and-merge-your-pull-request-commits)
  (squash all commits into a single commit). The default option is `merge`.
 
+- `MERGE_METHOD_LABELS`: Set to allow labels to determine the merge method.
+ For example, `automerge=merge,autosquash=squash,autorebase=rebase`.
+
+ If no such label is present, use `MERGE_METHOD`.
+
+- `MERGE_METHOD_LABEL_REQUIRED`: Set to `"true"` to require one of the
+ `MERGE_METHOD_LABELS` to be set.
+
 - `MERGE_COMMIT_MESSAGE`: The commit message to use when merging the pull
  request into the base branch. Possible values are `automatic` (use GitHub's
  default message), `pull-request-title` (use the pull request's title),

lib/common.js

@@ -69,6 +69,19 @@ function createConfig(env = {}) {
  };
  }
 
+ function parseMergeMethodLabels(str) {
+ if (!str) {
+ return [];
+ }
+ return str.split(",").map(lm => {
+ const [label, method] = lm.split("=");
+ if (!label || !method) {
+ throw new Error(`Couldn't parse ${lm} as label=method`);
+ }
+ return { label, method };
+ });
+ }
+
  function parseMergeRemoveLabels(str, defaultValue) {
  return (str == null ? defaultValue : str).split(",").map(s => s.trim());
  }
@@ -97,6 +110,8 @@ function createConfig(env = {}) {
  const mergeRetries = parsePositiveInt("MERGE_RETRIES", 6);
  const mergeRetrySleep = parsePositiveInt("MERGE_RETRY_SLEEP", 5000);
  const mergeDeleteBranch = env.MERGE_DELETE_BRANCH === "true";
+ const mergeMethodLabels = parseMergeMethodLabels(env.MERGE_METHOD_LABELS);
+ const mergeMethodLabelRequired = env.MERGE_METHOD_LABEL_REQUIRED === "true";
 
  const updateLabels = parseMergeLabels(env.UPDATE_LABELS, "automerge");
  const updateMethod = env.UPDATE_METHOD || "merge";
@@ -107,6 +122,8 @@ function createConfig(env = {}) {
  mergeLabels,
  mergeRemoveLabels,
  mergeMethod,
+ mergeMethodLabels,
+ mergeMethodLabelRequired,
  mergeForks,
  mergeCommitMessage,
  mergeCommitMessageRegex,

lib/merge.js

@@ -17,7 +17,8 @@ async function merge(context, pullRequest) {
  const {
  octokit,
  config: {
- mergeMethod,
+ mergeMethod: defaultMergeMethod,
+ mergeMethodLabels,
  mergeCommitMessage,
  mergeCommitMessageRegex,
  mergeFilterAuthor,
@@ -55,6 +56,11 @@ async function merge(context, pullRequest) {
  }
 
  const commitMessage = getCommitMessage(mergeCommitMessage, pullRequest);
+ const mergeMethod = getMergeMethod(
+ defaultMergeMethod,
+ mergeMethodLabels,
+ pullRequest
+ );
  const merged = await tryMerge(
  octokit,
  pullRequest,
@@ -143,7 +149,12 @@ async function deleteBranch(octokit, pullRequest) {
 
 function skipPullRequest(context, pullRequest) {
  const {
- config: { mergeForks, mergeLabels }
+ config: {
+ mergeForks,
+ mergeLabels,
+ mergeMethodLabelRequired,
+ mergeMethodLabels
+ }
  } = context;
 
  let skip = false;
@@ -181,6 +192,14 @@ function skipPullRequest(context, pullRequest) {
  }
  }
 
+ const numberMethodLabelsFound = mergeMethodLabels
+ .map(lm => labels.includes(lm.label))
+ .filter(x => x).length;
+ if (mergeMethodLabelRequired && numberMethodLabelsFound === 0) {
+ logger.info("Skipping PR merge, required merge method label missing");
+ skip = true;
+ }
+
  return skip;
 }
 
@@ -255,6 +274,26 @@ function tryMerge(
  );
 }
 
+function getMergeMethod(defaultMergeMethod, mergeMethodLabels, pullRequest) {
+ const foundMergeMethodLabels = pullRequest.labels.flatMap(l =>
+ mergeMethodLabels.filter(ml => ml.label === l.name)
+ );
+ if (foundMergeMethodLabels.length > 0) {
+ const first = foundMergeMethodLabels[0];
+ if (foundMergeMethodLabels.length > 1) {
+ logger.info(
+ `Discovered multiple merge method labels, will merge with method ${first.method}`
+ );
+ } else {
+ logger.info(
+ `Discovered ${first.label}, will merge with method ${first.method}`
+ );
+ }
+ return first.method;
+ }
+ return defaultMergeMethod;
+}
+
 function getCommitMessage(mergeCommitMessage, pullRequest) {
  if (mergeCommitMessage === "automatic") {
  return undefined;

test/common.test.js

@@ -13,6 +13,8 @@ test("createConfig", () => {
  blocking: [],
  required: []
  },
+ mergeMethodLabels: [],
+ mergeMethodLabelRequired: false,
  mergeForks: true,
  mergeCommitMessage: "automatic",
  mergeCommitMessageRegex: "",

test/merge.test.js

@@ -2,12 +2,13 @@ const { merge } = require("../lib/merge");
 const { createConfig } = require("../lib/common");
 const { pullRequest } = require("./common");
 
-let octokit;
+let octokit, mergeMethod;
 
 beforeEach(() => {
+ mergeMethod = undefined;
  octokit = {
  pulls: {
- merge: jest.fn()
+ merge: jest.fn(({ merge_method }) => (mergeMethod = merge_method))
  }
  };
 });
@@ -109,3 +110,82 @@ test("MERGE_FILTER_AUTHOR when set but do not match current author should not me
  // WHEN
  expect(await merge({ config, octokit }, pr)).toEqual(false);
 });
+
+test("Merge method can be set by env variable", async () => {
+ // GIVEN
+ const pr = pullRequest();
+
+ const config = createConfig({
+ MERGE_METHOD: "rebase"
+ });
+
+ // WHEN
+ expect(await merge({ config, octokit }, pr)).toEqual(true);
+ expect(mergeMethod).toEqual("rebase");
+});
+
+test("Merge method can be set by a merge method label", async () => {
+ // GIVEN
+ const pr = pullRequest();
+ pr.labels = [{ name: "autosquash" }, { name: "reallyautomerge" }];
+
+ const config = createConfig({
+ MERGE_METHOD_LABELS: "automerge=merge,autosquash=squash,autorebase=rebase",
+ MERGE_METHOD: "merge",
+ MERGE_LABELS: "reallyautomerge"
+ });
+
+ // WHEN
+ expect(await merge({ config, octokit }, pr)).toEqual(true);
+ expect(mergeMethod).toEqual("squash");
+});
+
+test("Merge method can be required", async () => {
+ // GIVEN
+ const pr = pullRequest();
+ pr.labels = [{ name: "autosquash" }];
+
+ const config = createConfig({
+ MERGE_METHOD_LABELS: "automerge=merge,autosquash=squash,autorebase=rebase",
+ MERGE_METHOD_LABEL_REQUIRED: "true",
+ MERGE_METHOD: "merge",
+ MERGE_LABELS: ""
+ });
+
+ // WHEN
+ expect(await merge({ config, octokit }, pr)).toEqual(true);
+ expect(mergeMethod).toEqual("squash");
+});
+
+test("Missing require merge method skips PR", async () => {
+ // GIVEN
+ const pr = pullRequest();
+ pr.labels = [{ name: "mergeme" }];
+
+ const config = createConfig({
+ MERGE_METHOD_LABELS: "automerge=merge,autosquash=squash,autorebase=rebase",
+ MERGE_METHOD_LABEL_REQUIRED: "true",
+ MERGE_METHOD: "merge",
+ MERGE_LABELS: "mergeme"
+ });
+
+ // WHEN
+ expect(await merge({ config, octokit }, pr)).toEqual(false);
+});
+
+test("Merge method doesn't have to be required", async () => {
+ // GIVEN
+ const pr = pullRequest();
+ pr.labels = [{ name: "mergeme" }];
+
+ const config = createConfig({
+ MERGE_METHOD_LABELS: "automerge=merge,autosquash=squash,autorebase=rebase",
+ MERGE_METHOD_LABEL_REQUIRED: "false",
+ MERGE_METHOD: "merge",
+ MERGE_LABELS: "mergeme"
+ });
+
+ // WHEN
+ expect(await merge({ config, octokit }, pr)).toEqual(true);
+ expect(mergeMethod).toEqual("merge");
+});