Preserve Short‑Form format When Generating YAML

[jimtng]

Preserve Short‑Form format When Generating YAML

openHAB already supports the short‑form format syntax for Items in YAML. For example:

items:
  itemname:
    format: '%d'

Internally, this is correctly translated into the equivalent metadata structure:

items:
  itemname:
    metadata:
      stateDescription:
        value: ''
        config:
          pattern: '%d'

However, when exporting or regenerating YAML from this internal representation, the system currently does not restore the short‑form. Instead, it always emits the full metadata block, even when the only metadata present is the pattern value that corresponds directly to the format shorthand.

This PR updates the YAML generator so that:

• If the stateDescription metadata contains only a pattern value,
  → the YAML generator emits the concise format: '<pattern>' form.
• If any additional stateDescription metadata is present,
  → the generator falls back to the full metadata representation.

✔️ Benefits

• Restores symmetry between input and output YAML.
• Keeps generated YAML clean, readable, and consistent with user‑authored files.
• Avoids unnecessary verbosity when only the format shorthand is needed.

[jimtng]

@lolodomo, when you have a moment, could you take a look at this? I want to make sure I’ve understood the override logic correctly, especially around the injected vs. default formats. I might be missing some of the intent from the original implementation, so your insight would be really helpful.

[lolodomo]

This case is very complex in particular due to the way it is managed by the DSL provider.
I remember I made a choice to be sure to not loose stuff after several conversions in both sense between YAML and DSL.

[lolodomo]

Looking at the code, I see that I did not consider the short form for format and I am sure it was a deliberate choice. I will have to remember and explain what kind of problem it can lead to.

[jimtng]

This whole default / injected stateFormatter logic seems strange to me. I would think the short form / long form should only relate to what's actually stored in the metadata and it should be done without any regard to any default / injected format from anywhere else.

[lolodomo]

This whole default / injected stateFormatter logic seems strange to me. I would think the short form / long form should only relate to what's actually stored in the metadata and it should be done without any regard to any default / injected format from anywhere else.

DSL provider does not use metadata but another feature. I remember I hesitated to change the DSL provider to remove that. I did not do it because I was not 100% of the possible impacts.

[lolodomo]

But let me remember the scenario which was a problem.
I agree your change would be of course better if only YAML is considered.

[Copilot]

Pull request overview

This pull request enhances the YAML generator for openHAB to preserve the short-form format syntax when exporting items. Previously, even when items were defined with the concise format: '%d' syntax, the generator would always expand this to the full metadata.stateDescription.config.pattern structure. This PR adds logic to detect when stateDescription metadata contains only a pattern value and generates the short-form instead, maintaining symmetry between input and output YAML.

Changes:

• Added logic to convert stateDescription metadata with only a pattern config back to short-form format field
• Refactored metadata handling to use early continue statements for improved readability
• Added comprehensive tests for both short-form and long-form stateDescription scenarios

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 4 comments.

File	Description
YamlItemFileConverter.java	Refactored metadata handling logic to detect and preserve short-form format syntax when appropriate; simplified control flow with early continue statements
YamlItemFileConverterTest.java	Added tests to verify stateDescription metadata conversion to short-form format and long-form preservation when additional config exists

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[lolodomo]

@openhab/core-maintainers : please wait before merging, I would like to investigate more.

[jimtng]

rebased to resolve conflict

[lolodomo]

Need to find again the use case that will be problematic with DSL.
My intention is to change the DSL provider in 5.3 to allow this change.