Add @conditions, smithy-model-jmespath, NodeValidationPlugin SPI by robin-aws · Pull Request #2935 · smithy-lang/smithy

robin-aws · 2026-01-20T04:18:50Z

Background

What do these changes do?
- The main contribution is @conditions, the first "contract trait", which specifies JMESPath expressions that must evaluate to true.
- To support this:
  - Adds smithy-model-jmespath, to contain a JmespathRuntime<T> adaptor for Node values.
  - Adds an SPI for NodeValidatorPlugin so that packages outside of smithy-model can provide additional node validation.
  - Optimizes NodeValidationVisitor to index NodeValidatorPlugins by ShapeType, to improve on the current approach that invokes all 10 existing plugins for every node regardless of type.
  - Moved the two existing copies of ModelRuntimeTypeGenerator and tests into smithy-model-jmespath, to avoid having to define a third copy.
Why are they important?
- This trait helps both humans and LLMs understand correct use of APIs better, especially constraints that are already manually checked in a service but not otherwise encoded/documented in the model. We reviewed an internal design doc on this that I could add to this PR if desired.

Testing

How did you test these changes?
- Existing NodeValidationVisitor tests for the optimization.
- New tests in smithy-model-jmespath and smithy-contracts

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

github-actions · 2026-01-20T04:19:05Z

This pull request does not contain a staged changelog entry. To create one, use the ./.changes/new-change command. For example:

./.changes/new-change --pull-requests "#2935" --type feature --description "Add @conditions, smithy-model-jmespath, NodeValidationPlugin SPI"

Make sure that the description is appropriate for a changelog entry and that the proper feature type is used. See ./.changes/README or run ./.changes/new-change -h for more information.

docs/source-2.0/spec/contract-traits.rst

.changes/next-release/feature-077b7f1cd574ee78042363f8d8c3afb20d56f081.json

smithy-contract-traits/src/main/resources/META-INF/smithy/contracts.smithy

docs/source-2.0/spec/contract-traits.rst

smithy-model/src/main/java/software/amazon/smithy/model/shapes/ShapeTypeFilter.java

smithy-model/src/main/java/software/amazon/smithy/model/shapes/ShapeTypeMap.java

smithy-contracts/src/main/java/software/amazon/smithy/contracts/ConditionsTraitValidator.java

...mespath/src/main/java/software/amazon/smithy/model/jmespath/node/ModelJmespathUtilities.java

Co-authored-by: Kevin Stich <kevin@kstich.com>

smithy-contract-traits/src/main/resources/META-INF/smithy/contracts.smithy

smithy-contract-traits/src/main/java/software/amazon/smithy/contracts/Condition.java

kstich · 2026-01-29T06:22:25Z

...contract-traits/src/main/java/software/amazon/smithy/contracts/ConditionsTraitValidator.java

+    private List<
+            ValidationEvent> validateCondition(Model model, Shape shape, String conditionName, Condition condition) {


Did the code formatter really do this?

It did! I put the parameters on separate lines and that avoided it.

…ntracts/Condition.java Co-authored-by: Kevin Stich <kevin@kstich.com>

…hy into smithy-contracts-squashed

mtdowling · 2026-01-30T17:19:40Z

...el/src/main/java/software/amazon/smithy/model/validation/node/MemberAndShapeTraitPlugin.java

 import software.amazon.smithy.model.traits.Trait;

-abstract class MemberAndShapeTraitPlugin<S extends Shape, N extends Node, T extends Trait>
+public abstract class MemberAndShapeTraitPlugin<N extends Node, T extends Trait>


Does this need to be public for this PR?

It's beneficial because ConditionsTraitPlugin extends it, and doesn't live in smithy-model. I'd expect most plugins to be based on some trait so most will also want to extend this.

Oh but it needs Javadoc in that case, so I added that.

mtdowling · 2026-01-30T17:37:19Z

...hy-model/src/main/java/software/amazon/smithy/model/validation/node/NodeValidatorPlugin.java

+     * @return A {@link BiPredicate} that returns true if this plugin
+     *         has an effect on Node values of the given shape.
+     */
+    default BiPredicate<Model, Shape> shapeMatcher() {


You made a ShapeTypeFilter plugin. Why not replace this method with ShapeTypeFilter getFilter()?

I was intending to leave the door open to optimize further in the future, indexing by individual shape rather than just shape type. With this signature plugins can filter more precisely if they want.

I could make the return type ShapeTypeFilter for now, since I could replace that with a supertype later without breaking folks. But I wouldn't want to make the name more specific since I can't change that later.

Or rather if I make it getFilter() now, I might end having to add a default BiPredicate<Model, Shape> shapeMatcher() method later.

Discussed offline and the opportunity cost is just not that high realistically, so I made the change. :)

.../src/main/java/software/amazon/smithy/model/validation/node/NonNumericFloatValuesPlugin.java

…ugin

Add @conditions, smithy-model-jmespath, NodeValidationPlugin SPI

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robin-aws requested a review from a team as a code owner January 20, 2026 04:18

robin-aws requested a review from kstich January 20, 2026 04:18

robin-aws added 2 commits January 19, 2026 20:20

Feature

3682b03

Make @conditions a map instead of a list

c733e5a

yasmewad requested a review from mtdowling January 23, 2026 17:33

kstich requested changes Jan 26, 2026

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robin-aws and others added 4 commits January 26, 2026 11:47

Apply suggestions from code review

5293120

Co-authored-by: Kevin Stich <kevin@kstich.com>

Fix build after PR edits

53307c0

PR feedback

f0d555e

A bit more Javadoc

8644b15

kstich reviewed Jan 27, 2026

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smithy-contract-traits/src/main/resources/META-INF/smithy/contracts.smithy Show resolved Hide resolved

robin-aws added 4 commits January 27, 2026 15:31

Fix breaks from removing getParsedExpression()

739c82e

description -> documentation, fix tests

9346581

Wafer-thin javadoc

9fdfe28

smithydoc

576b4ae

kstich reviewed Jan 29, 2026

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robin-aws and others added 4 commits January 29, 2026 07:35

Fix weird autoformat

9bd77ed

Update smithy-contract-traits/src/main/java/software/amazon/smithy/co…

58632cb

…ntracts/Condition.java Co-authored-by: Kevin Stich <kevin@kstich.com>

Update smithy-contract-traits/src/main/java/software/amazon/smithy/co…

5079293

…ntracts/Condition.java Co-authored-by: Kevin Stich <kevin@kstich.com>

Merge branch 'smithy-contracts-squashed' of github.com:robin-aws/smit…

fa27a72

…hy into smithy-contracts-squashed

kstich approved these changes Jan 29, 2026

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mtdowling reviewed Jan 30, 2026

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robin-aws added 2 commits January 30, 2026 10:15

Make ShapeTypeFilters static finals where possible

16714fd

shapeMatcher() -> shapeTypeFilter(), Javadoc on MemberAndShapeTraitPl…

9bf9f1c

…ugin

mtdowling approved these changes Jan 30, 2026

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Second release note

8bce774

kstich merged commit 9fa0f35 into smithy-lang:main Feb 2, 2026
13 checks passed

		private List<
		ValidationEvent> validateCondition(Model model, Shape shape, String conditionName, Condition condition) {

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robin-aws commented Jan 20, 2026 •

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