Show warnings about unmerged parent pull requests (#18)

* Show dependency warning under PR body

* add feature to readme

README.md

@@ -22,6 +22,13 @@
 |<img alt="Only relevant changes visible" src="./.github/only-relevant.png" height="200px" />|
 |--|
 
+<p align="center">
+  <strong>Automatic warnings on sequential pull requests</strong>
+</p>
+
+|<img alt="Automatic warnings on sequential pull requests" src="./.github/warning.png" />|
+|--|
+
 
 ## Workflow
 

src/features/merge-warning.tsx

@@ -0,0 +1,68 @@
+import { h } from "dom-chef";
+import { getPullRequests } from "../api";
+import {
+  createIdForPullRequest,
+  getBasePullRequestWithStackerInfo
+} from "../lib/base";
+import { IStackerContext } from "../lib/context";
+import { getBodyTextarea } from "../lib/dom";
+import { getLocation, getPullRequestURL } from "../lib/location";
+import { getStackerInfo } from "../lib/prInfo";
+
+function getTextareaStackerInfo() {
+  const $textarea = getBodyTextarea();
+  return $textarea && getStackerInfo($textarea.value);
+}
+const WARNING_ID = "stacker-merge-warning";
+export default async function initialize(context: IStackerContext) {
+  const $comment = document.querySelector(".comment-body");
+
+  const location = getLocation(context.location);
+
+  const pullRequests = await getPullRequests(context.accessToken)(
+    location.ownerLogin,
+    location.repoName
+  );
+
+  const stackerInfo = getTextareaStackerInfo();
+  const basePR =
+    stackerInfo && getBasePullRequestWithStackerInfo(stackerInfo, pullRequests);
+
+  // Handle existing warning
+  const $warning = document.getElementById(WARNING_ID);
+  if ($warning) {
+    if (!basePR) {
+      // Clear existing warning
+      $warning.remove();
+      return;
+    }
+
+    if (
+      createIdForPullRequest(basePR) ===
+      $warning.getAttribute("data-stacker-pr")
+    ) {
+      // Keep existing warning
+      return;
+    }
+  }
+
+  if (!(stackerInfo && $comment && $comment.firstElementChild)) {
+    return;
+  }
+
+  if (!basePR) {
+    return;
+  }
+
+  $comment.insertBefore(
+    <p id={WARNING_ID} data-stacker-pr={createIdForPullRequest(basePR)}>
+      ⚠️ &nbsp;This pull request depends on{" "}
+      <strong>
+        <a href={getPullRequestURL(basePR)} target="_blank">
+          #{basePR.number} {basePR.title}
+        </a>
+      </strong>. Consider merging it before merging this one.
+    </p>,
+    $comment.firstElementChild.nextSibling
+  );
+}

src/features/parent-pr-select/index.tsx

@@ -10,6 +10,7 @@ import {
   getBasePullRequestWithStackerInfo
 } from "../../lib/base";
 import { IStackerContext } from "../../lib/context";
+import { getBodyTextarea } from "../../lib/dom";
 import {
   getLocation,
   isNewPullRequestView,
@@ -22,19 +23,15 @@ function updateTextareaValue(newParent: IGithubPullRequest) {
   const newStackerInfo = {
     baseBranch: createIdForPullRequest(newParent)
   };
-  const $textarea = document.querySelector(
-    'textarea[name="pull_request[body]"]'
-  ) as HTMLTextAreaElement;
+
+  const $textarea = getBodyTextarea();
   if ($textarea) {
     $textarea.value = updateStackerInfo($textarea.value, newStackerInfo);
   }
 }
 
 function getTextareaStackerInfo() {
-  const $textarea = document.querySelector(
-    'textarea[name="pull_request[body]"]'
-  ) as HTMLTextAreaElement | null;
-
+  const $textarea = getBodyTextarea();
   return $textarea && getStackerInfo($textarea.value);
 }
 

src/index.tsx

@@ -1,6 +1,7 @@
 import { UnauthorizedError } from "./api";
 import diffSelect from "./features/diff-select";
 import fadeOutUnrelatedCommits from "./features/fade-out-unrelated-commits";
+import mergeWarning from "./features/merge-warning";
 import parentPRSelect from "./features/parent-pr-select";
 import showStackingInList from "./features/show-stacking-in-list";
 import { setConfig } from "./lib/config";
@@ -17,6 +18,7 @@ async function run() {
     await showStackingInList(context);
     await parentPRSelect(context);
     await fadeOutUnrelatedCommits(context);
+    await mergeWarning(context);
   } catch (err) {
     if (err instanceof UnauthorizedError) {
       const token = window.prompt("Please enter an access token");

src/lib/dom.ts

@@ -0,0 +1,11 @@
+export function getBodyTextarea(): HTMLTextAreaElement | null {
+  return document.querySelector(
+    'textarea[name="pull_request[body]"]'
+  ) as HTMLTextAreaElement | null;
+}
+
+export function getBodyTextareaValue(): string | null {
+  const $textarea = getBodyTextarea();
+
+  return $textarea && $textarea.value;
+}

src/lib/location.ts

@@ -1,3 +1,5 @@
+import { IGithubPullRequest } from "../api";
+
 export interface ILocation {
   ownerLogin: string;
   repoName: string;
@@ -44,3 +46,9 @@ export function getOwner(location: Location) {
 export function getRepo(location: Location) {
   return getLocation(location).repoName;
 }
+
+export function getPullRequestURL(pullRequest: IGithubPullRequest) {
+  return `/${pullRequest.base.repo.owner.login}/${
+    pullRequest.base.repo.name
+  }/pull/${pullRequest.number}`;
+}