feat: support running builder functions locally (#3507)

src/commands/functions/serve.js

@@ -40,7 +40,8 @@ class FunctionsServeCommand extends Command {
       siteUrl,
       capabilities,
       timeouts,
-      prefix: '/.netlify/functions/',
+      functionsPrefix: '/.netlify/functions/',
+      buildersPrefix: '/.netlify/builders/',
     })
   }
 }

src/lib/functions/server.js

@@ -40,7 +40,7 @@ const buildClientContext = function (headers) {
 const createHandler = function ({ functionsRegistry }) {
   return async function handler(request, response) {
     // handle proxies without path re-writes (http-servr)
-    const cleanPath = request.path.replace(/^\/.netlify\/functions/, '')
+    const cleanPath = request.path.replace(/^\/.netlify\/(functions|builders)/, '')
     const functionName = cleanPath.split('/').find(Boolean)
     const func = functionsRegistry.get(functionName)
 
@@ -108,18 +108,30 @@ const createHandler = function ({ functionsRegistry }) {
     } else {
       const { error, result } = await func.invoke(event, clientContext)
 
+      // check for existence of metadata if this is a builder function
+      if (/^\/.netlify\/(builders)/.test(request.path) && (!result.metadata || !result.metadata.builder_function)) {
+        response.status(400).send({
+          message:
+            'Function is not an on-demand builder. See https://ntl.fyi/create-builder for how to convert a function to a builder.',
+        })
+        response.end()
+        return
+      }
+
       handleSynchronousFunction(error, result, response)
     }
   }
 }
 
-const getFunctionsServer = function ({ functionsRegistry, siteUrl, prefix }) {
+const getFunctionsServer = function ({ functionsRegistry, siteUrl, functionsPrefix, buildersPrefix }) {
   // performance optimization, load express on demand
   // eslint-disable-next-line node/global-require
   const express = require('express')
   // eslint-disable-next-line node/global-require
   const expressLogging = require('express-logging')
   const app = express()
+  const functionHandler = createHandler({ functionsRegistry })
+
   app.set('query parser', 'simple')
 
   app.use(
@@ -140,12 +152,22 @@ const getFunctionsServer = function ({ functionsRegistry, siteUrl, prefix }) {
     res.status(204).end()
   })
 
-  app.all(`${prefix}*`, createHandler({ functionsRegistry }))
+  app.all(`${functionsPrefix}*`, functionHandler)
+  app.all(`${buildersPrefix}*`, functionHandler)
 
   return app
 }
 
-const startFunctionsServer = async ({ config, settings, site, siteUrl, capabilities, timeouts, prefix = '' }) => {
+const startFunctionsServer = async ({
+  config,
+  settings,
+  site,
+  siteUrl,
+  capabilities,
+  timeouts,
+  functionsPrefix = '',
+  buildersPrefix = '',
+}) => {
   const internalFunctionsDir = await getInternalFunctionsDir({ base: site.root })
 
   // The order of the function directories matters. Leftmost directories take
@@ -165,7 +187,8 @@ const startFunctionsServer = async ({ config, settings, site, siteUrl, capabilit
     const server = getFunctionsServer({
       functionsRegistry,
       siteUrl,
-      prefix,
+      functionsPrefix,
+      buildersPrefix,
     })
 
     await startWebServer({ server, settings })

src/utils/proxy.js

@@ -28,7 +28,7 @@ const isInternal = function (url) {
   return url.startsWith('/.netlify/')
 }
 const isFunction = function (functionsPort, url) {
-  return functionsPort && url.match(/^\/.netlify\/functions\/.+/)
+  return functionsPort && url.match(/^\/.netlify\/(functions|builders)\/.+/)
 }
 
 const getAddonUrl = function (addonsUrls, req) {

tests/command.dev.test.js

@@ -158,6 +158,7 @@ testMatrix.forEach(({ args }) => {
           return {
             statusCode: 200,
             body: 'ping',
+            metadata: { builder_function: true },
           }
         },
       })
@@ -167,6 +168,36 @@ testMatrix.forEach(({ args }) => {
       await withDevServer({ cwd: builder.directory, args }, async (server) => {
         const response = await got(`${server.url}/.netlify/functions/timeout`).text()
         t.is(response, 'ping')
+        const builderResponse = await got(`${server.url}/.netlify/builders/timeout`).text()
+        t.is(builderResponse, 'ping')
+      })
+    })
+  })
+
+  test(testName('should fail when no metadata is set for builder function', args), async (t) => {
+    await withSiteBuilder('site-with-misconfigured-builder-function', async (builder) => {
+      builder.withNetlifyToml({ config: { functions: { directory: 'functions' } } }).withFunction({
+        path: 'builder.js',
+        handler: async () => ({
+          statusCode: 200,
+          body: 'ping',
+        }),
+      })
+
+      await builder.buildAsync()
+
+      await withDevServer({ cwd: builder.directory, args }, async (server) => {
+        const response = await got(`${server.url}/.netlify/functions/builder`)
+        t.is(response.body, 'ping')
+        t.is(response.statusCode, 200)
+        const builderResponse = await got(`${server.url}/.netlify/builders/builder`, {
+          throwHttpErrors: false,
+        })
+        t.is(
+          builderResponse.body,
+          `{"message":"Function is not an on-demand builder. See https://ntl.fyi/create-builder for how to convert a function to a builder."}`,
+        )
+        t.is(builderResponse.statusCode, 400)
       })
     })
   })
@@ -178,6 +209,7 @@ testMatrix.forEach(({ args }) => {
         handler: async () => ({
           statusCode: 200,
           body: 'ping',
+          metadata: { builder_function: true },
         }),
       })
 
@@ -186,6 +218,8 @@ testMatrix.forEach(({ args }) => {
       await withDevServer({ cwd: builder.directory, args }, async (server) => {
         const response = await got(`${server.url}/.netlify/functions/echo`).text()
         t.is(response, 'ping')
+        const builderResponse = await got(`${server.url}/.netlify/builders/echo`).text()
+        t.is(builderResponse, 'ping')
       })
     })
   })
@@ -200,6 +234,7 @@ testMatrix.forEach(({ args }) => {
           handler: async () => ({
             statusCode: 200,
             body: `${process.env.TEST}`,
+            metadata: { builder_function: true },
           }),
         })
 
@@ -208,6 +243,8 @@ testMatrix.forEach(({ args }) => {
       await withDevServer({ cwd: builder.directory, args }, async (server) => {
         const response = await got(`${server.url}/.netlify/functions/env`).text()
         t.is(response, 'FROM_DEV_FILE')
+        const builderResponse = await got(`${server.url}/.netlify/builders/env`).text()
+        t.is(builderResponse, 'FROM_DEV_FILE')
       })
     })
   })
@@ -219,6 +256,7 @@ testMatrix.forEach(({ args }) => {
         handler: async () => ({
           statusCode: 200,
           body: `${process.env.TEST}`,
+          metadata: { builder_function: true },
         }),
       })
 
@@ -227,6 +265,8 @@ testMatrix.forEach(({ args }) => {
       await withDevServer({ cwd: builder.directory, env: { TEST: 'FROM_PROCESS_ENV' }, args }, async (server) => {
         const response = await got(`${server.url}/.netlify/functions/env`).text()
         t.is(response, 'FROM_PROCESS_ENV')
+        const builderResponse = await got(`${server.url}/.netlify/builders/env`).text()
+        t.is(builderResponse, 'FROM_PROCESS_ENV')
       })
     })
   })
@@ -242,6 +282,7 @@ testMatrix.forEach(({ args }) => {
           handler: async () => ({
             statusCode: 200,
             body: `${process.env.TEST}`,
+            metadata: { builder_function: true },
           }),
         })
 
@@ -250,6 +291,8 @@ testMatrix.forEach(({ args }) => {
       await withDevServer({ cwd: builder.directory, args }, async (server) => {
         const response = await got(`${server.url}/.netlify/functions/env`).text()
         t.is(response, 'FROM_CONFIG_FILE')
+        const builderResponse = await got(`${server.url}/.netlify/builders/env`).text()
+        t.is(builderResponse, 'FROM_CONFIG_FILE')
       })
     })
   })
@@ -1818,6 +1861,7 @@ export const handler = async function () {
             body: '',
             headers: { 'single-value-header': 'custom-value' },
             multiValueHeaders: { 'multi-value-header': ['custom-value1', 'custom-value2'] },
+            metadata: { builder_function: true },
           }),
         })
         .buildAsync()
@@ -1826,6 +1870,9 @@ export const handler = async function () {
         const response = await got(`${server.url}/.netlify/functions/custom-headers`)
         t.is(response.headers['single-value-header'], 'custom-value')
         t.is(response.headers['multi-value-header'], 'custom-value1, custom-value2')
+        const builderResponse = await got(`${server.url}/.netlify/builders/custom-headers`)
+        t.is(builderResponse.headers['single-value-header'], 'custom-value')
+        t.is(builderResponse.headers['multi-value-header'], 'custom-value1, custom-value2')
       })
     })
   })