Adds meta name="generator" check to upgrade plugin

.eleventy.js

@@ -14,6 +14,8 @@ module.exports = function(eleventyConfig) {
   console.log(chalk.blue(`[11ty/eleventy-upgrade-help]`), `If you are migrating from 0.x or 1.x, please use a previous version of this plugin.`);
   console.log(chalk.blue(`[11ty/eleventy-upgrade-help] ---`));
 
+  eleventyConfig.addPlugin(require("./src/meta-generator.js"));
+
   // Full list of issues: https://github.com/11ty/eleventy/issues?q=milestone%3A%22Eleventy+3.0.0%22+is%3Aclosed+label%3Abreaking-change
   eleventyConfig.addPlugin(require("./src/node-version.js"));
   eleventyConfig.addPlugin(require("./src/explicit-config-file.js"));

package.json

@@ -33,6 +33,7 @@
     "fast-glob": "^3.3.2",
     "kleur": "^4.1.5",
     "minimist": "^1.2.8",
+    "posthtml-match-helper": "^2.0.2",
     "semver": "^7.6.3"
   },
   "11ty": {

src/meta-generator.js

@@ -0,0 +1,44 @@
+const chalk = require("kleur");
+
+module.exports = async function(eleventyConfig) {
+	const { default: matchHelper } = await import("posthtml-match-helper");
+
+	let htmlTemplatesMissingMetaGenerator = new Set();
+	let found = 0;
+
+	eleventyConfig.on("eleventy.before", () => {
+		htmlTemplatesMissingMetaGenerator = new Set();
+		found = 0;
+	});
+
+	eleventyConfig.on("eleventy.after", () => {
+		if(htmlTemplatesMissingMetaGenerator.size > 0) {
+			console.log(chalk.blue(`[11ty/eleventy-upgrade-help] NOTICE`), `Your project has .html output files (×${htmlTemplatesMissingMetaGenerator.size}) that don’t have a populated <meta name="generator" content> tag. It would be helpful to Eleventy if you added it (but isn’t required). Applicable input files: ${Array.from(htmlTemplatesMissingMetaGenerator).join(", ")} Read more: https://www.11ty.dev/docs/data-eleventy-supplied/#use-with-meta-namegenerator`);
+		} else {
+			console.log(chalk.green(`[11ty/eleventy-upgrade-help] PASSED`), `All of your project’s .html output files (×${found}) are using <meta name="generator" content="Eleventy …">`);
+		}
+	});
+
+	eleventyConfig.htmlTransformer.addPosthtmlPlugin(
+		"html",
+		function (options) {
+			return function (tree) {
+				let missing = 1;
+
+				tree.match(matchHelper(`meta[name="generator"]`), function (node) {
+					if (node.attrs?.content && (node.attrs?.content || "").toLowerCase().startsWith("eleventy")) {
+						missing--;
+					}
+
+					return node;
+				});
+
+				if(missing > 0) {
+					htmlTemplatesMissingMetaGenerator.add(options.page.inputPath);
+				} else {
+					found++;
+				}
+			};
+		}
+	);
+};