DevTools AutoReload Support

[jamesward]

I'd like to use Spring Shell with Spring DevTools for auto-reload. (Relates to some Embabel issues I've encountered: embabel/embabel-agent#1133)

Currently a basic application gets into a wonky state after reload (https://github.com/jamesward/hello-spring-shell/tree/devtools)

./gradlew bootRun
> Task :checkKotlinGradlePluginConfigurationErrors SKIPPED
> Task :compileKotlin UP-TO-DATE
> Task :compileJava NO-SOURCE
> Task :processResources NO-SOURCE
> Task :classes UP-TO-DATE
> Task :resolveMainClassName

> Task :bootRun

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/

 :: Spring Boot ::                (v4.0.0)

2025-12-12T11:42:56.008-07:00  INFO 67950 --- [  restartedMain] com.example.demo.DemoApplicationKt       : Starting DemoApplicationKt using Java 21.0.9 with PID 67950 (/home/jw/projects/hello/hello-spring-shell/build/classes/kotlin/main started by jw in /home/jw/projects/hello/hello-spring-shell)
2025-12-12T11:42:56.010-07:00  INFO 67950 --- [  restartedMain] com.example.demo.DemoApplicationKt       : No active profile set, falling back to 1 default profile: "default"
2025-12-12T11:42:56.042-07:00  INFO 67950 --- [  restartedMain] .e.DevToolsPropertyDefaultsPostProcessor : Devtools property defaults active! Set 'spring.devtools.add-properties' to 'false' to disable
2025-12-12T11:42:56.372-07:00  WARN 67950 --- [  restartedMain] org.jline                                : Unable to create a system terminal, creating a dumb terminal (enable debug logging for more information)
2025-12-12T11:42:56.438-07:00  INFO 67950 --- [  restartedMain] com.example.demo.DemoApplicationKt       : Started DemoApplicationKt in 0.638 seconds (process running for 0.842)
shell:>hello
hello, world!!!
shell:>2025-12-12T11:43:40.752-07:00  INFO 67950 --- [   File Watcher] rtingClassPathChangeChangedEventListener : Restarting due to 3 class path changes (0 additions, 0 deletions, 3 modifications)

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/

 :: Spring Boot ::                (v4.0.0)

2025-12-12T11:43:40.796-07:00  INFO 67950 --- [  restartedMain] com.example.demo.DemoApplicationKt       : Starting DemoApplicationKt using Java 21.0.9 with PID 67950 (/home/jw/projects/hello/hello-spring-shell/build/classes/kotlin/main started by jw in /home/jw/projects/hello/hello-spring-shell)
2025-12-12T11:43:40.797-07:00  INFO 67950 --- [  restartedMain] com.example.demo.DemoApplicationKt       : No active profile set, falling back to 1 default profile: "default"
2025-12-12T11:43:40.867-07:00  WARN 67950 --- [  restartedMain] org.jline                                : Unable to create a system terminal, creating a dumb terminal (enable debug logging for more information)
2025-12-12T11:43:40.877-07:00  INFO 67950 --- [  restartedMain] com.example.demo.DemoApplicationKt       : Started DemoApplicationKt in 0.092 seconds (process running for 45.282)
shell:>hello
Command hl not found
Available commands: 

	hello: say hello
Built-In Commands
	help: Display help about available commands
	version: Show version info
	clear: Clear the terminal screen

shell:>

[fmbenhassine]

Thank you for reporting this issue @jamesward !

Can you please tell me how you trigger a reload? I mean this:

shell:>2025-12-12T11:43:40.752-07:00  INFO 67950 --- [   File Watcher] rtingClassPathChangeChangedEventListener : Restarting due to 3 class path changes (0 additions, 0 deletions, 3 modifications)

I tried changing the code of the command itself (println("hello, world!!!") -> println("hello, world!!!!!")) and also changing a dependency in the class path (Boot 4.0.0 -> 4.0.1) and then rebuild the project while running the app both in the IDE (IntelliJ IDEA) and in a different terminal with Gradle but no luck. I also tried to add the properties to setup a file system watcher as documented in Spring Boot but still no luck.

Moreover, the output is completely broken with that gradle command:

2025-12-23T07:25:51.106+01:00  INFO 89372 --- [  restartedMain] com.example.demo.DemoApplicationKt       : Started DemoApplicationKt in 0.726 seconds (process running for 0.875)
shell:>
<======shell:>> 85% EXECUTING [4s]
> :bootRun    shell:>
<<==<===========--> 8hello, world!!!s]
shell:>
<======shell:>> 85% EXECUTING [10s]
> :bootRun    shell:>
<===========--> 85% EXECUTING [1m 4s]

Just as an FYI, we released 4.0 RC1 last week, so it would be great if you give it a try (a few things have changed since 4.0-M2 that is used in the reproducer). I am not sure it will fix this issue, but I will test this auto reload support as well on my side. Thank you upfront!