Claus Ibsen created CAMEL-25562:
-----------------------------------
Summary: Camel 5 - YAML DSL: write each branch of a choice as its
own when, as the Java and XML DSLs do
Key: CAMEL-25562
URL: https://issues.apache.org/jira/browse/CAMEL-25562
Project: Camel
Issue Type: Improvement
Components: camel-yaml-dsl
Reporter: Claus Ibsen
h3. The trap
In the Java and XML DSLs, a choice has a when for each branch:
{code:java}
.choice()
.when(simple("${header.country} == 'DK'")).log("local")
.when(simple("${header.country} == 'DE'")).log("eu")
.otherwise().log("export")
.end()
{code}
In the YAML DSL, a choice has one {{when:}} key, and the branches are its list:
{code:yaml}
- choice:
when:
- simple: "${header.country} == 'DK'"
steps:
- log: local
- simple: "${header.country} == 'DE'"
steps:
- log: eu
otherwise:
steps:
- log: export
{code}
Whoever writes YAML with the Java or XML habit, people and AI models alike,
writes a {{when:}} for each branch. YAML has no repeated keys: the YAML DSL
keeps the last {{when:}} and drops the branches before it, without an error.
The local-model benchmark hit this: a choice with two {{when:}} keys ran with
one branch.
CAMEL-25560 makes the validator report a key given twice and say how to merge
the branches. The shape itself stays a trap, and changing it breaks every YAML
choice, so it is for Camel 5.
h3. Goal
Each branch of a choice is written as its own entry, as in the Java and XML
DSLs, so a branch cannot replace another one.
h3. To decide
* *The shape.* For example, a list of {{- when:}} and {{- otherwise:}} items,
as the children of the XML {{<choice>}} element are, and where the options of
the choice itself ({{id}}, {{precondition}}) go next to that list.
* *The other EIPs with the same pattern*, where XML repeats a child element and
YAML lists the children under one key: {{doTry}} with {{doCatch:}}, the REST
DSL verbs ({{get:}}, {{post:}}, ...) and others. Decide them as one set, so the
YAML DSL keeps one style.
* *Migration of existing YAML routes*: accept the 4.x shape in 5.0 with a
deprecation warning, and/or an OpenRewrite recipe in camel-upgrade-recipes.
* *What reads and writes the shape*: the YAML DSL JSON schema (classic and
canonical), the generated YAML DSL deserializers, camel-yaml-io (the YAML
writer), the validator and its hints, the documentation and examples, and
tooling such as Kaoto.
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