add custom build task contribution sample

bookshop/package.json

@@ -8,6 +8,9 @@
     "express": "^4.17.1",
     "passport": "0.4.1"
   },
+  "devDependencies": {
+    "@cds/cds-plugin-openapi": "*"
+  },
   "scripts": {
     "genres": "cds serve test/genres.cds",
     "start": "cds run",

cds-plugin-openapi/index.js

@@ -0,0 +1,29 @@
+/* eslint-disable require-await */
+const cds = require('@sap/cds'), { BuildTaskHandler } = cds.build
+const cdsdk = require('@sap/cds-dk')
+
+cds.build.register(class OpenApiHandler extends BuildTaskHandler {
+    static get meta() {
+        return {
+            id: 'openapi',
+            runWith: ['node-cf', 'java-cf'],
+            config: { src: cds.env.folders.srv.replace(/\/$/, '') }
+        }
+    }
+    async clean() {
+        return this.remove('openapi-docs')
+    }
+    async build() {
+        const model = await this.model()
+        const { options } = this.task
+
+        // generate openapi files for all services
+        await Promise.all(cds.linked(model).services.map(service => {
+            const openApi = cdsdk.compile.to.openapi(model, {
+                service: service.name,
+                'openapi:diagram': String(options.diagram) === 'true'
+            })
+            this.write(openApi).to(`openapi-docs/${service.name}.openapi3.json`)
+        }))
+    }
+})

cds-plugin-openapi/package.json

@@ -0,0 +1,9 @@
+{
+  "name": "@sap/cds-plugin-openapi",
+  "version": "1.0.0",
+  "description": "OpenAPI service specification build plugin",
+  "main": "index.js",
+  "dependencies": {
+    "@sap/cds-dk": "^4"
+  }
+}

package.json

@@ -13,13 +13,14 @@
     "@capire/media": "./media",
     "@capire/orders": "./orders",
     "@capire/reviews": "./reviews",
-    "@sap/cds": "^5.5.3"
+    "@sap/cds": "git+https://github.tools.sap/cap/cds#add/customBuildTaskProviders"
   },
   "devDependencies": {
     "chai": "^4.3.4",
     "chai-as-promised": "^7.1.1",
     "chai-subset": "^1.6.0",
-    "sqlite3": "^5"
+    "sqlite3": "^5",
+    "@cds/cds-plugin-openapi": "./cds-plugin-openapi"
   },
   "scripts": {
     "cleanup": "rm -rf node_modules && rm -rf */node_modules && rm -rf */*/node_modules",