[Streams] Propagate the ingest pipeline access pattern flag to the ingest document

[jbaiera]

Adds the ability for an ingest document to capture the pipeline's access pattern flag when executing the pipeline on the document. The document stores the access pattern flag in a stack to allow for holding and restoring the access pattern flag when running nested pipelines.

[elasticsearchmachine]

Pinging @elastic/es-data-management (Team:Data Management)

[masseyke]

Is it intentional that this method isn't used above (and seems to only be used in the test)?

[jbaiera]

not used above yet. I'm currently using it in a couple places in the next set of changes I'm working on.

[masseyke]

LGTM

[Copilot]

Pull Request Overview

This PR introduces tracking of each pipeline’s access pattern within nested pipeline executions by maintaining a stack on the ingest document. Key changes include:

• Add accessPatternStack field and related push/pop logic in IngestDocument
• Update Pipeline class to allow mocking by removing final
• Introduce a comprehensive nested-access-pattern test in IngestDocumentTests

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
server/src/main/java/org/elasticsearch/ingest/IngestDocument.java	Added accessPatternStack, push/pop logic, and getCurrentAccessPattern()
server/src/main/java/org/elasticsearch/ingest/Pipeline.java	Removed final modifier from Pipeline for testability
server/src/test/java/org/elasticsearch/ingest/IngestDocumentTests.java	Added testNestedAccessPatternPropagation with Mockito captures

Comments suppressed due to low confidence (2)

server/src/main/java/org/elasticsearch/ingest/Pipeline.java:28

• [nitpick] Removing final from Pipeline makes it extendable, which may not be intended for core pipeline behavior; verify that this aligns with the project's API design.

public class Pipeline {

server/src/test/java/org/elasticsearch/ingest/IngestDocumentTests.java:1273

• The test uses is(empty()) but is is not statically imported; add import static org.hamcrest.Matchers.is; to avoid a compilation error.

        assertThat(document.getPipelineStack(), is(empty()));

[Copilot]

Relying on a Java assert means this check is skipped unless assertions are enabled; consider throwing an explicit exception or using a proper validation mechanism to ensure consistency in all environments.

Suggested change

	assert previousAccessPattern == accessPatternStack.peek()
	: "Cleared access pattern from nested pipeline and found inconsistent stack state. Expected ["
	+ previousAccessPattern
	+ "] but found ["
	+ accessPatternStack.peek()
	+ "]";
	if (previousAccessPattern != accessPatternStack.peek()) {
	throw new IllegalStateException(
	"Cleared access pattern from nested pipeline and found inconsistent stack state. Expected ["
	+ previousAccessPattern
	+ "] but found ["
	+ accessPatternStack.peek()
	+ "]"
	);
	}

[Copilot]

Using poll() ignores the returned element and silently handles an empty stack; consider using pop() or removeFirst() for clearer intent and to fail-fast on unexpected underflow.

Suggested change

	accessPatternStack.poll();
	accessPatternStack.pop();

[Copilot]

There is a typo in the Javadoc: THe should be The.

Suggested change

	* Despite what the comment above says, we're copying it here anyway. THe reason is that this constructor is only called from
	* Despite what the comment above says, we're copying it here anyway. The reason is that this constructor is only called from