Add a page listing recipes by tag

src/main/kotlin/org/openrewrite/RecipeMarkdownGenerator.kt

@@ -292,6 +292,7 @@ class RecipeMarkdownGenerator : Runnable {
         createModerneRecipes(outputPath, moderneProprietaryRecipes)
         createRecipesWithDataTables(recipesWithDataTables, outputPath)
         createScanningRecipes(allRecipes.filter { it is ScanningRecipe<*> && it !is DeclarativeRecipe }, outputPath)
+        createRecipesByTag(allRecipeDescriptors, outputPath)
         createStandaloneRecipes(allRecipeDescriptors, outputPath)
 
         // Write the README.md for each category
@@ -1126,7 +1127,8 @@ import TabItem from '@theme/TabItem';
                     } else if (tag.lowercase().startsWith("rspec-")) {
                         writeln("* [$tag](https://sonarsource.github.io/rspec/#/rspec/S${tag.substring(6)})")
                     } else {
-                        writeln("* $tag")
+                        val tagAnchor = tag.lowercase().replace(" ", "-")
+                        writeln("* [$tag](../recipes-by-tag#${tagAnchor})")
                     }
                 }
                 newLine()
@@ -2385,6 +2387,59 @@ $cliSnippet
         }
     }
 
+    private fun createRecipesByTag(allRecipeDescriptors: List<RecipeDescriptor>, outputPath: Path) {
+        val tagToRecipes = TreeMap<String, TreeSet<RecipeDescriptor>>(String.CASE_INSENSITIVE_ORDER)
+
+        // Collect all tags and their associated recipes
+        for (recipeDescriptor in allRecipeDescriptors) {
+            for (tag in recipeDescriptor.tags) {
+                tagToRecipes.computeIfAbsent(tag) { TreeSet(compareBy { it.name }) }
+                    .add(recipeDescriptor)
+            }
+        }
+
+        val markdown = outputPath.resolve("recipes-by-tag.md")
+        Files.newBufferedWriter(markdown, StandardOpenOption.CREATE).useAndApply {
+            writeln(
+                //language=markdown
+                """
+                ---
+                description: An autogenerated list of all recipe tags and the recipes within each tag.
+                ---
+
+                # Recipes by Tag
+
+                _This doc contains all recipe tags and the recipes that are tagged with them._
+
+                """.trimIndent()
+            )
+
+            if (tagToRecipes.isEmpty()) {
+                writeln("No tagged recipes found.")
+            } else {
+                writeln("Total tags: ${tagToRecipes.size}\n")
+
+                for ((tag, recipes) in tagToRecipes) {
+                    writeln("## ${tag}")
+                    writeln("\n_${recipes.size} recipe${if (recipes.size != 1) "s" else ""}_\n")
+
+                    for (recipe in recipes) {
+                        val displayName = recipe.displayName.replace("`", "")
+                        writeln(
+                            "* [${displayName}](../recipes/${getRecipePath(recipe)}.md) - _${
+                                recipe.description.replace(
+                                    "\n",
+                                    " "
+                                )
+                            }_"
+                        )
+                    }
+                    writeln("")
+                }
+            }
+        }
+    }
+
     private fun createStandaloneRecipes(allRecipeDescriptors: List<RecipeDescriptor>, outputPath: Path) {
         // Skip if there are no recipes to process
         if (allRecipeDescriptors.isEmpty()) {

src/test/kotlin/org/openrewrite/RecipeMarkdownGeneratorTest.kt

@@ -25,6 +25,7 @@ class RecipeMarkdownGeneratorTest {
 
             "8.x", // Rewrite
             "2.x", // Recipe BOM
+            "1.x", // Moderne Recipe BOM
             "6.x", // Gradle plugin
             "5.x", // Maven plugin
         )