Validate build.edge_handlers exists

package.json

@@ -27,6 +27,7 @@
     "@types/node": "^14.0.27",
     "make-dir": "^3.1.0",
     "node-fetch": "^2.6.1",
+    "path-type": "^4.0.0",
     "rollup": "^2.23.1",
     "typescript": "^3.9.7"
   },

src/index.js

@@ -8,6 +8,7 @@ const commonjs = require("@rollup/plugin-commonjs");
 const json = require("@rollup/plugin-json");
 const nodeResolve = require("@rollup/plugin-node-resolve");
 const makeDir = require("make-dir");
+const { isDirectory } = require("path-type");
 const rollup = require("rollup");
 
 const babel = nodeBabel.babel;
@@ -165,6 +166,10 @@ function serializeHandler(handler) {
 
 module.exports = {
   onPostBuild: async ({ constants: { IS_LOCAL, NETLIFY_API_TOKEN, EDGE_HANDLERS_SRC }, utils }) => {
+    if (!(await isDirectory(EDGE_HANDLERS_SRC))) {
+      return utils.build.failBuild(`Edge handlers directory does not exist: ${EDGE_HANDLERS_SRC}`);
+    }
+
     const { mainFile, handlers } = await assemble(EDGE_HANDLERS_SRC);
 
     if (handlers.length === 0) {

test/fixtures/wrong-config-dir/netlify.toml

@@ -0,0 +1,5 @@
+[build]
+edge_handlers = "does-not-exist"
+
+[[plugins]]
+package = "../../.."

test/main.js

@@ -7,6 +7,7 @@ const { runNetlifyBuild } = require("./helpers/run");
 const INTEGRATION_TEST_DIR = `${__dirname}/../integration-test`;
 const FIXTURES_DIR = `${__dirname}/fixtures`;
 const CONFIG_FIXTURE_DIR = `${FIXTURES_DIR}/config-dir`;
+const WRONG_CONFIG_FIXTURE_DIR = `${FIXTURES_DIR}/wrong-config-dir`;
 
 test("Edge handlers should be bundled", async (t) => {
   await runNetlifyBuild(t, INTEGRATION_TEST_DIR);
@@ -29,3 +30,8 @@ test("Edge handlers directory can be configured using build.edge_handlers", asyn
   const { manifest } = loadBundle(t, CONFIG_FIXTURE_DIR);
   t.deepEqual(manifest.handlers, ["example"]);
 });
+
+test("Edge handlers directory build.edge_handlers misconfiguration is reported", async (t) => {
+  const { output } = await runNetlifyBuild(t, WRONG_CONFIG_FIXTURE_DIR, { expectedSuccess: false });
+  t.true(output.includes("does-not-exist"));
+});