[2528] Export successions with an implicit target inline

[HuiJun]

Symptom

A succession written with the then shorthand and an implicit target (the next body member) is exported as a dangling then; followed by the target on its own line, which is invalid SysML v2:

// reference
action a1;
then decide;
// exported
action a1;
then;
decide ;

This is #2528 (Batmobile template export); the same happens in state definitions (first X then;, the first item of #2429). Additionally an unnamed composite DecisionNode is exported as decide ; (trailing space).

Root cause

• The target EndFeatureMembership owns a bare ReferenceUsage with no (or only implied) ReferenceSubsetting: the target is implicitly the following member. caseSuccessionAsUsage always emitted then followed by appendConnectorEndMember, which has nothing to emit for such an end. The implicit source case was already handled (isSuccessionUsageImplicitSource), the target case was not.
• caseDecisionNode appended "decide " with a hard-coded trailing space before an (empty) declaration.

Fix

SysMLElementSerializer:

• isSuccessionUsageImplicitSource is generalized to isImplicitEnd (unnamed ReferenceUsage whose specializations are all implied) and used for both ends.
• New getNextMembership / getImplicitSuccessionTarget: when the next not-yet-serialized member of the owning type is an ActionUsage (incl. control nodes, states; TransitionUsage excluded) and the target end is implicit or references exactly that member, the member is serialized inline as then <member> and added to childrenMembershipToSkip so it is not emitted a second time. This produces then decide;, then merge;, then fork;, then join;, then action x {...}, then state s2;.
• Implicit target with no usable following member: nothing is emitted for the succession (no dangling then;) and a warning is reported through reportConsumer.
• A body on a succession with an inlined target cannot be represented; it is dropped with a warning.
• caseDecisionNode emits decide via appendWithSpaceIfNeeded like the other keywords.

Tests

• SysMLElementSerializerTest: successionUsageWithImplicitControlNodeTargets (then decide; / then merge;), successionUsageWithImplicitNamedActionTarget (then action a_2;), successionUsageWithImplicitTargetInStateDefinition (then state s2;), successionUsageWithImplicitTargetAndNoFollowingMember (no output + warning), successionUsageWithExplicitSourceAndUnresolvedImplicitTarget (succession omitted instead of a partial first a1;), decisionNodeWithoutName.
• ImportExportTests: new checkSuccessionWithImplicitTargets round trip (then decide;, then merge;, then action a3;); checkDecisionWithNamedTransition and the then action expectation updated to the inline form.
• CHANGELOG.adoc entry added.

Fixes #2528. Also fixes the first X then; item of #2429 (the other items of that issue are not covered). Part of #2213.

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[AxelRICHARD]

Hello,

Thank your for providing this PR.
Could you also sign the Eclipse Contributor Agreement (ECA) https://www.eclipse.org/legal/eca/ please ? I won't be able to merge the PR if you don't sign it, because SysON is a project of the Eclipse Foundation.

If this PR is related to #2429 as it seems to be, please add a comment on this issue saying that you want to work on this issue. I will affect it to you.

Also it seems you added a fix for #2213. Please provide a separate PR for this issue and add a comment on this issue saying that you want to work on this issue. I will affect it to you.

Then I will perform a review.

Thank you for your understanding.

Regards,

[AxelRICHARD]

Hello @HuiJun,

Here is my review:

• Possible data loss: the serializer (backend/services/syson-sysml-metamodel-services/src/main/java/org/eclipse/syson/sysml/metamodel/services/textual/SysMLElementSerializer.java:1338) drops a succession with an explicit source when its following target is unnamed. It reports a warning, but the exported model loses that connection. The warning also says there is “no following action” when one exists. For a complete fix, give the unnamed target a unique name in the exported text and reference it: first source then generatedName; followed by decide generatedName;. Named targets already use this form in the PR’s tests. Generate the name for serialization without changing the model, and test that importing the result preserves the connection.
• Existing body content can be lost: the inline branch (backend/services/syson-sysml-metamodel-services/src/main/java/org/eclipse/syson/sysml/metamodel/services/textual/SysMLElementSerializer.java:1371) warns about remaining succession children but does not serialize them. Previously, the serializer wrote that content. This needs either preservation or a test establishing that such content cannot occur.
• Please squash all your commit to only provide one
• Please update the doc/content/modules/user-manual/pages/release-notes/2026.11.0.adoc release note

Thank you!

[HuiJun]

Done! Sorry for the delay in responding!

[AxelRICHARD]

Done! Sorry for the delay in responding!

Hello @HuiJun, there is no problem, you can take all the time you need for taking into account my remarks et comments.