Remove nodemon from dev server lifecycle by infomiho · Pull Request #4407 · wasp-lang/wasp

infomiho · 2026-07-01T08:02:13Z

Description

Remove nodemon from the generated development server. wasp start now owns the server process, decides when it needs updating, and cleans it up itself.

This fixes stale server processes after a failed compile or bundle. It also avoids restarting a healthy server when a recompile did not change anything the server uses.

Closes #1844.

Server effects

Every successful recompile produces one ServerEffect:

Effect	Meaning
`NoServerEffect`	Keep the current server.
`RestartServer`	Restart the existing bundle, for example after `.env` changes.
`RebundleAndRestartServer`	Build a new server bundle, then replace the server.

When several files change together, the strongest required effect wins.

The effect is based on both the saved project files and the generated files whose checksums actually changed. A main.wasp.ts save alone does not restart the server. If that edit changes generated server/src, server/package.json, or server/.env, it does.

Trade-off: generated SDK paths are ignored. We assume every server-relevant SDK change also changes generated server source or a project src runtime input.

Server process controller

The controller owns the current server process and handles compile results one at a time:

Result	Action
Compile fails	Stop the server and keep `wasp start` running.
Server inputs are unchanged	Keep the current server.
Only runtime configuration changes	Restart without bundling.
Server inputs change and bundle succeeds	Replace the server.
Server inputs change and bundle fails	Stop the server and keep `wasp start` running.

If the server exits by itself, the controller cleans up any surviving descendants and waits for the next successful compile.

Managed subprocesses

Wasp.Job.Subprocess.spawn starts a child process whose lifetime is tied to its Job. Releasing it stops the whole owned process tree, drains or closes output, and waits for cleanup before returning.

The platform-specific process-tree work lives in Wasp.Job.Subprocess.System: process groups and signals on Unix, process jobs on Windows, and Linux /proc checks for zombie-only groups.

wasp start also installs graceful SIGINT/SIGTERM handling so process cleanup finishes before Wasp exits.

Review map

Just code moving:

Shared process-test helpers move into Test.Process.Util; their behavior is unchanged.

Generated or mechanical changes:

Example lockfiles only reflect removing the generated nodemon dependency.
E2E snapshots were regenerated after deleting nodemon.json and changing the generated server package scripts.
CLI command signature edits mostly thread the compile hooks and server controller through existing flows.

Not just a rename:

The old long-running process code is split into managed lifecycle code and platform-specific system code. The public API also changes so cleanup is owned by Job resources.

Type of change

🔧 Just code/docs improvement
🐞 Bug fix
🚀 New/improved feature
💥 Breaking change

Checklist

pkg-pr-new · 2026-07-01T08:13:12Z

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infomiho · 2026-07-01T12:49:18Z

 import qualified Wasp.Job as J
 import Wasp.Job.Except (ExceptJob, toExceptJob)
-import Wasp.Job.Process (runNodeCommandAsJob, runNodeCommandAsJobWithExtraEnv)
+import Wasp.Job.Node (runNodeCommandAsJob, runNodeCommandAsJobWithExtraEnv)


There were some Node.js specific bits that got mixed with generic process handling, so I separated them.

infomiho · 2026-07-02T13:34:44Z

+#if !mingw32_HOST_OS
+import qualified System.Posix.Signals as Signals
+#endif
+
+withGracefulTermination :: IO a -> IO a
+#if mingw32_HOST_OS
+withGracefulTermination = id
+#else
+withGracefulTermination action = do
+  targetThreadId <- myThreadId
+  let interruptCurrentCommand = Signals.Catch $ throwTo targetThreadId UserInterrupt
+  bracket
+    (mapM (installHandler interruptCurrentCommand) [Signals.sigINT, Signals.sigTERM])
+    restoreHandlers
+    (const action)
+  where
+    installHandler handler signal = do
+      previousHandler <- Signals.installHandler signal handler Nothing
+      return (signal, previousHandler)
+
+    restoreHandlers =
+      mapM_ $ \(signal, previousHandler) ->
+        Signals.installHandler signal previousHandler Nothing
+#endif


This is the wildest bit of the implementation - to enable cleanup after wasp start is interrupted.

Why is bracket not enough?
Also, I am adding Resourcet to Command in #4504, might that be useful?

infomiho · 2026-07-02T13:35:47Z

@@ -0,0 +1,29 @@
+module Wasp.Util.Glob


Extract from waspignore module. Shared between waspignore and server path watching.

infomiho · 2026-07-02T13:37:45Z

 -- Also makes sure to remove any redundant file drafts that have been left on the disk from before.
 -- It is smart when writing, so it doesn't write file drafts that are already written on the disk from before.
-synchronizeFileDraftsWithDisk :: Path' Abs (Dir GeneratedAppDir) -> [FileDraft] -> IO ()
+synchronizeFileDraftsWithDisk :: Path' Abs (Dir GeneratedAppDir) -> [FileDraft] -> IO [GeneratedAppPathChange]


After sync file drafts, we return a list of written and deleted files. The idea is to be able to detect which generated files changes happened so we can react to it e.g. restart the server process.

cprecioso

Random comments, didn't do proper review yet

cprecioso · 2026-07-22T08:49:11Z

 ### 🐞 Bug fixes

 - Fixed a race condition where `useAuth()` could return stale user data after an action that modifies the `User` entity (by @okxint). ([#4343](https://github.com/wasp-lang/wasp/issues/4343))
+- `wasp start` now manages the development server process directly instead of relying on the generated server's `nodemon`, improving restart behavior. ([#4407](https://github.com/wasp-lang/wasp/pull/4407))


nitpick

Suggested change

- `wasp start` now manages the development server process directly instead of relying on the generated server's `nodemon`, improving restart behavior. ([#4407](https://github.com/wasp-lang/wasp/pull/4407))

- `wasp start` now manages the development server process directly instead with `nodemon`, improving stability. ([#4407](https://github.com/wasp-lang/wasp/pull/4407))

cprecioso · 2026-07-22T08:50:41Z

@@ -1 +1 @@
-`npm start` to run server in development mode (it reloads on changes).
+`npm start` runs the already bundled server in development mode. Use `wasp start` for automatic rebuilds and restarts while developing.


I'd remove the wasp start note straight away. Users either see this in production or don't see it in development.
I might even remove the README.

cprecioso · 2026-07-22T08:54:21Z

+devServerStartExecutable = "node"
+
+devServerStartArgs :: [String]
+devServerStartArgs = ["--enable-source-maps", "-r", "dotenv/config", "bundle/server.js"]


prolly not for now but: https://nodejs.org/docs/latest-v24.x/api/environment_variables.html#cli-options

cprecioso · 2026-07-22T08:55:13Z

+devServerStartExecutable :: String
+devServerStartExecutable = "node"


nitpick i'd make the command + args just a single array, we can head it later. or a tuple at least. it doesn't make sense to define one thing without the other IMO

cprecioso · 2026-07-22T08:58:17Z

+devServerStartCommand :: String
+devServerStartCommand = unwords $ devServerStartExecutable : devServerStartArgs


and we could just unwords this in the callsite, we "don't know" here yet where this will be used and each callsite is in charge of formatting multiple arguments and escaping spaces etc.

cprecioso · 2026-07-22T08:58:50Z

not reviewing this yet, maybe the review on #4500 makes it easier

cprecioso · 2026-07-22T09:00:04Z

+#if mingw32_HOST_OS
+stopProcessTree processHandle rootExitAsync _ = do
+  void (try (P.terminateProcess processHandle) :: IO (Either SomeException ()))
+  waitForAsync rootExitAsync hardStopTimeoutMicroseconds
+#else


I'd extract the system-specific parts into their own module (e.g. Job.Process.LongRunning.System), so the templated functions are more scoped to a single place instead of mixed with "regular" code

cprecioso · 2026-07-22T09:12:00Z

+recursiveFileGlobsWithExtensions :: FilePath -> [String] -> [String]
+recursiveFileGlobsWithExtensions dir extensions =
+  (\ext -> dir FP.</> "**" FP.</> "*" ++ ext) <$> extensions
+
+dirAndDescendantsGlobs :: FilePath -> [String]
+dirAndDescendantsGlobs dir =
+  [ dir,
+    dir FP.</> "**" FP.</> "*"
+  ]


Patterns are Monoids, so we can use its type directly and <> instead of FilePaths, which is not semantically accurate. Plus the semantic helpers at System.FilePath.Glob.Primitive. We can use / directly since it's the only valid separator for globs, independently of the system:

Suggested change

recursiveFileGlobsWithExtensions :: FilePath -> [String] -> [String]

recursiveFileGlobsWithExtensions dir extensions =

(\ext -> dir FP.</> "**" FP.</> "*" ++ ext) <$> extensions

dirAndDescendantsGlobs :: FilePath -> [String]

dirAndDescendantsGlobs dir =

[ dir,

dir FP.</> "**" FP.</> "*"

]

recursiveFileGlobsWithExtensions :: Pattern -> [String] -> [Patterns]

recursiveFileGlobsWithExtensions dir extensions =

((dir <> "/**/*" <>) . literal) <$> extensions

dirAndDescendantsGlobs :: Pattern -> [Pattern]

dirAndDescendantsGlobs dir =

[ dir,

dir <> "/**/*"

]

(i tried it in GHCi and it all works as expected)

cprecioso · 2026-07-22T09:22:43Z

  Path' Abs (Dir Generator.GeneratedAppDir) ->
  CompileOptions ->
-  IO ([CompileWarning], [CompileError])
+  IO CompileResult


Seems like what we actually want is a

type Compilation = ExceptT CompileError (WriterT [CompileWarning] IO) [FileOrDirPathRelativeTo Generator.GeneratedAppDir]

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View reviewed changes

infomiho added 7 commits July 29, 2026 11:57

Remove nodemon from dev server lifecycle

542ef69

Use job output sinks for server processes

f9096f3

Share process test utilities

fe57b14

Integrate managed subprocesses with jobs

388b371

Update managed subprocess output sinks

d3d005b

Handle server bundle exit explicitly

5c07a89

Regenerate snapshots after trunk rebase

ef380f5

infomiho mentioned this pull request Jul 29, 2026

Migrate subprocesses to Data.Conduit.Process.Typed #4575

Open

	- `wasp start` now manages the development server process directly instead of relying on the generated server's `nodemon`, improving restart behavior. ([#4407](https://github.com/wasp-lang/wasp/pull/4407))
	- `wasp start` now manages the development server process directly instead with `nodemon`, improving stability. ([#4407](https://github.com/wasp-lang/wasp/pull/4407))

		@@ -1 +1 @@
		`npm start` to run server in development mode (it reloads on changes).
		`npm start` runs the already bundled server in development mode. Use `wasp start` for automatic rebuilds and restarts while developing.

		devServerStartExecutable :: String
		devServerStartExecutable = "node"

		devServerStartCommand :: String
		devServerStartCommand = unwords $ devServerStartExecutable : devServerStartArgs

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Description

Server effects

Server process controller

Managed subprocesses

Review map

Type of change

Checklist

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