fix: omit duplicate functions from list of bundled files

packages/build/src/plugins_core/functions/utils.js

@@ -16,7 +16,9 @@ const getRelativeFunctionMainFiles = async function ({ featureFlags, functionsSr
 
   const zisiFeatureFlags = getZisiFeatureFlags(featureFlags)
   const functions = await listFunctions(functionsSrc, { featureFlags: zisiFeatureFlags })
-  return functions.map(({ mainFile }) => relative(functionsSrc, mainFile))
+  const dedupedFunctions = new Map(functions.map((func) => [func.name, func]))
+  const relativeMainFiles = [...dedupedFunctions.values()].map(({ mainFile }) => relative(functionsSrc, mainFile))
+  return relativeMainFiles
 }
 
 export const getUserAndInternalFunctions = ({

packages/build/tests/core/fixtures/functions_duplicate_names/netlify/functions/function_one.js

@@ -0,0 +1 @@
+export const handler = () => true

packages/build/tests/core/fixtures/functions_duplicate_names/netlify/functions/function_one.ts

@@ -0,0 +1 @@
+export const handler = () => true

packages/build/tests/core/tests.js

@@ -589,6 +589,12 @@ test('Bundles functions from the `.netlify/functions-internal` directory even if
   t.snapshot(normalizeOutput(output))
 })
 
+test('Removes duplicate function names from the list of processed functions', async (t) => {
+  const output = await new Fixture('./fixtures/functions_duplicate_names').runWithBuild()
+  t.true(normalizeOutput(output).includes(`- function_one.js`))
+  t.false(normalizeOutput(output).includes(`- function_one.ts`))
+})
+
 test.serial('`rustTargetDirectory` is passed to zip-it-and-ship-it only when running in buildbot', async (t) => {
   const runCount = 4
   const mockZipFunctions = sinon.stub().resolves()