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 +1,51 @@
+/* eslint-disable require-await */
+const path = require("path")
+const fs = require("fs")
+const cds = require('@sap/cds'), { BuildTaskProvider, BuildTaskHandler } = cds.build
+const cdsdk = require('@sap/cds-dk')
+const { path4 } = cds.serve
+const logger = cds.log("build")
+
+module.exports.activate = () => {
+    cds.build.registerProvider(
+        new (class extends BuildTaskProvider {
+            get id() {
+                return 'openapi'
+            }
+            get dependents() {
+                return ['node-cf', 'java-cf']
+            }
+            applyTaskDefaults(task) {
+                task.src = task.src || cds.env.folders.srv.replace(/\/$/, '')
+            }
+            async lookupTasks() {
+                if (process.env.NODE_ENV === 'production') {
+                    return [{ for: this.id }]
+                }
+            }
+            get handler() {
+                return class extends BuildTaskHandler {
+                    async clean() {
+                        fs.rm(path.join(this.task.dest, "gen/docs"), { recursive: true, force: true }, (err) => logger.error(err))
+                    }
+
+                    async build() {
+                        const model = await this.model()
+                        const { options } = this.task
+
+                        // generate openapi files for all services
+                        await Promise.all(cds.linked(model).services.map(service => {
+                            const openApi = cdsdk.compile.to.openapi(model, {
+                                service: service.name,
+                                'openapi:url': path4(service).replace(/\.[^.]+$/, ''),
+                                'openapi:diagram': options.diagram
+                            })
+
+                            this.write(openApi).to(`gen/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

@@ -12,14 +12,15 @@
     "@capire/media": "./media",
     "@capire/orders": "./orders",
     "@capire/reviews": "./reviews",
-    "@sap/cds": "^5.1.5"
+    "@sap/cds": "git+https://github.tools.sap/cap/cds#add/customBuildTaskProviders"
   },
   "devDependencies": {
     "cds-swagger-ui-express": "^0.2.0",
     "chai": "^4.2.0",
     "chai-as-promised": "^7.1.1",
     "chai-subset": "^1.6.0",
-    "sqlite3": "^5.0.0"
+    "sqlite3": "^5.0.0",
+    "@cds/cds-plugin-openapi": "./cds-plugin-openapi"
   },
   "scripts": {
     "cleanup": "rm -rf node_modules && rm -rf */node_modules && rm -rf */*/node_modules",