Infinite loops in /api/rest/projects/{projectId}/commits/{commitId}/roots and /api/.../elements response generation

[ctmbl]

originally posted as a comment of #4414

---

• I have checked that this bug has not yet been reported by someone else
• I have checked that this bug appears on Chrome
• I have specified the version :

• d4df511

• I have specified my environment :

• WSL

Screenshots

...

Steps to reproduce

• create a Blank Studio with a simple Entity containing itself:
  
• access http://localhost:8080/api/rest/projects/<your-project-id>/commits/<your-project-id>/roots

OR

• create a new project from the Flow template
• access http://localhost:8080/api/rest/projects/<your-project-id>/commits/<your-project-id>/roots

Expected behavior

• don't create an infinite loop in the backend => don't reach nesting limit
• return valid JSON
• don't return duplicated elements in the JSON (cf example below with standard and Processor1 from the Flow template through target -> incomingFlows -> target)

Actual behavior

/api/rest/projects/{projectId}/commits/{commitId}/roots and /api/rest/projects/{projectId}/commits/{commitId}/elements suffers from infinite loop and return not valid JSON because of a nesting depth limit reached in the backend:

2025-01-16T11:52:22.259+01:00  WARN 4604 --- [io-8080-exec-10] .w.s.m.s.DefaultHandlerExceptionResolver : Ignoring exception, response committed already: org.springframework.http.converter.HttpMessageNotWritableException: Could not write JSON: Document nesting depth (1001) exceeds the maximum allowed (1000, from `StreamWriteConstraints.getMaxNestingDepth()`)
2025-01-16T11:52:22.259+01:00  WARN 4604 --- [io-8080-exec-10] .w.s.m.s.DefaultHandlerExceptionResolver : Resolved [org.springframework.http.converter.HttpMessageNotWritableException: Could not write JSON: Document nesting depth (1001) exceeds the maximum allowed (1000, from `StreamWriteConstraints.getMaxNestingDepth()`)]

returning (in the case of the Flow template):

[
    {
        "consumption": 0,
        "powerStatus": "NONE",
        "status": "ACTIVE",
        "usage": "UNUSED",
        "outgoingFlows": [],
        "name": "NewSystem",
        "elements": [
            {
                "consumption": 0,
                "powerStatus": "NONE",
                "status": "ACTIVE",
                "usage": "UNUSED",
                "outgoingFlows": [],
                "name": "CompositeProcessor1",
                "elements": [
                    {
                        "status": "ACTIVE",
                        "usage": "UNUSED",
                        "incomingFlows": [
                            {
                                "status": "ACTIVE",
                                "usage": "STANDARD",
                                "capacity": 6,
                                "load": 6,
                                "target": {
                                    "status": "ACTIVE",
                                    "usage": "UNUSED",
                                    "incomingFlows": [
                                        {
                                            "status": "ACTIVE",
                                            "usage": "STANDARD",
                                            "capacity": 6,
                                            "load": 6,
                                            "target": {
                                                "status": "ACTIVE",
                                                "usage": "UNUSED",
                                                "incomingFlows": [
                                                    {
                                                        "status": "ACTIVE",
                                                        "usage": "STANDARD",
                                                        "capacity": 6,
                                                        "load": 6,
                                                        "target": {
                                                            "status": "ACTIVE",
                                                            "usage": "UNUSED",
                                                            "incomingFlows": [
                                                                {
                                                                    "status": "ACTIVE",
                                                                    "usage": "STANDARD",
                                                                    "capacity": 6,
                                                                    "load": 6,
                                                                    "target": {
... (goes on and on through target -> incomingFlows -> target)