Initial

.github/workflows/example.yml

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+name: Capture Vercel preview URL
+
+on:
+  pull_request:
+    branches:
+      - master
+    types: [opened]
+  issue_comment:
+    types: [edited]
+
+jobs:
+  capture_vercel_preview_url:
+    name: Capture Vercel preview URL
+    runs-on: "ubuntu-latest"
+    steps:
+      - uses: aaron-binary/vercel-preview-url-action@master
+        id: vercel_preview_url

.gitignore

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+node_modules

.prettierignore

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+node_modules
+dist

README.MD

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+# Overview
+
+Capture a Vercel preview URL and feed it into your next GitHub action.
+
+1. This action runs whenever an edit is made to a pull request comment (see `example.yml` below).
+2. It checks whether the editor of the comment is Vercel's bot account on GitHub.
+3. It attempts to extract the preview URL from the comment and sets it as the action's output so that you can feed it into your next action.
+
+Please note that the action only succeeds when a preview URL was found, it fails on every other event (each edit made on a pull request comment will run this action).
+
+## Inputs
+
+- `vercel_bot_name`: The name of the Vercel account commenting on pull requests. (default: `vercel[bot]`)
+- `preview_url_regexp`: Regular expression pattern (without delimiters) to capture the preview URL. Ensure first capture group captures the preview URL. (default: `Preview: \[(.*)\]`)
+
+## Outputs
+
+- `vercel_preview_url`: The preview URL which can be accessed in the next action through the `needs` context, e.g. `${{needs.capture_vercel_preview_url.outputs.vercel_preview_url}}` ([Read more](https://docs.github.com/en/free-pro-team@latest/actions/reference/context-and-expression-syntax-for-github-actions#needs-context))
+
+## Example
+
+```YML
+name: Capture Vercel preview URL
+
+on:
+  pull_request:
+    branches:
+      - master
+    types: [opened]
+  issue_comment:
+    types: [edited]
+
+jobs:
+  capture_vercel_preview_url:
+    name: Capture Vercel preview URL
+    runs-on: "ubuntu-latest"
+    steps:
+      - uses: aaron-binary/vercel-preview-url-action@master
+        id: vercel_preview_url
+```

action.yml

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+name: "Capture Vercel Preview URL"
+author: "Aaron Imming <aaim@protonmail.com>"
+description: "Capture a Vercel preview URL and feed it into your next GitHub action."
+branding:
+  icon: "triangle"
+  color: "black"
+inputs:
+  vercel_bot_name:
+    description: "The name of the Vercel account commenting on pull requests."
+    required: false
+    default: "vercel[bot]"
+  preview_url_regexp:
+    description: "Regular expression pattern to capture the preview URL. Ensure first capture group captures the preview URL."
+    required: false
+    default: 'Preview: \[(.*)\]' # Do use single quotes, do NOT use delimiters.
+outputs:
+  vercel_preview_url:
+    description: "The preview URL for the pull request's Vercel deployment."
+runs:
+  using: "node12"
+  main: "dist/index.js"

index.js

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+const core = require("@actions/core");
+const github = require("@actions/github");
+
+const runAction = async () => {
+  const { payload } = github.context;
+  const { comment } = payload;
+  const vercel_bot_name = core.getInput("vercel_bot_name");
+
+  if (comment.user.login !== vercel_bot_name) {
+    console.log("Comment did not originate from Vercel bot.", {
+      vercel_bot_name,
+    });
+    process.exit(1);
+  }
+
+  const preview_url_regexp = new RegExp(core.getInput("preview_url_regexp"));
+  const regex_matches = comment.body.match(preview_url_regexp);
+
+  if (!regex_matches) {
+    console.log("Unable to find a preview URL in comment's body.");
+    process.exit(1);
+  }
+
+  const vercel_preview_url = regex_matches[1];
+
+  if (vercel_preview_url) {
+    console.log("Found preview URL.", { vercel_preview_url });
+    core.setOutput("vercel_preview_url", vercel_preview_url);
+    process.exit(0);
+  } else {
+    console.log(
+      "The regular expression is in an invalid format. Please ensure the first capture group caputures the preview URL."
+    );
+    process.exit(1);
+  }
+};
+
+runAction();