Support Validation of union types

[steiler]

This PR fixes validation gaps for YANG leaves defined as union types.

Today, union branch selection happens at import time (XML/JSON/proto): the server tries branches in order and stores the first successfully parsed TypedValue. Later, validation runs against the outer union schema type instead of the specific matched branch type. Because the outer union type does not carry branch-specific constraints, several validators can no-op unexpectedly.

Problem
For union-typed leaves, the current validation path can miss real violations:

Pattern and length checks read constraints from the outer union type, which has none.
Range checks read constraints from the outer union type, which has none.
Leafref checks look for a leafref path on the outer union type, which is empty.
This means values that actually matched a leafref branch can bypass live-tree reference validation, allowing dangling references to pass undetected.

[Copilot]

Pull request overview

This PR closes validation gaps for YANG union-typed leaves by carrying the resolved union member type alongside the parsed TypedValue, and updating validators to enforce member-specific constraints (pattern/length/range/leafref) across JSON/XML/proto/default/defaults/intent-expansion ingress paths.

Changes:

• Add union-member attribution plumbing (MatchedUnionType / EffectiveLeafType) from import/conversion through tree updates.
• Update validators to validate against the effective (matched) leaf type rather than the outer union type, plus add broad parity/regression tests.
• Extend the test YANG model with union leaves and pin sdc-protos to a commit containing new union helper APIs.

Reviewed changes

Copilot reviewed 38 out of 39 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
tests/schema/sdcio_model.yang	Adds union-typed leaves covering pattern/length/range/leafref scenarios.
pkg/utils/testhelper/testhelpers.go	Adapts helper to new converter expansion return type.
pkg/utils/converter.go	Introduces ExpandedUpdate with matched union member metadata during expansion.
pkg/utils/converter_test.go	Adds unit tests for matched union member propagation in converter expansion.
pkg/tree/types/update.go	Stores matched union member type on types.Update and uses it in intent expansion.
pkg/tree/types/update_test.go	Adds tests for EffectiveLeafType / matched type behavior and copying/equality.
pkg/tree/types/update_slice.go	Preserves matched union member type when copying updates across owners/priorities.
pkg/tree/types/update_slice_test.go	Tests matched-type preservation during UpdateSlice copy.
pkg/tree/processors/processor_importer.go	Captures matched union member type from import adapters on leaf updates.
pkg/tree/ops/validation/validation_union_xml_json_parity_test.go	Adds JSON vs canonical XML re-import parity coverage for unions.
pkg/tree/ops/validation/validation_union_range_test.go	Adds union range validation coverage.
pkg/tree/ops/validation/validation_union_proto_roundtrip_test.go	Adds proto round-trip parity tests for union validation outcomes.
pkg/tree/ops/validation/validation_union_leafref_test.go	Adds union leafref validation coverage.
pkg/tree/ops/validation/validation_union_leafref_optional_test.go	Adds optional-instance union leafref warning/error behavior coverage.
pkg/tree/ops/validation/validation_test_helpers_test.go	Adds shared import helpers for union validation test matrix.
pkg/tree/ops/validation/validation_intent_expand_union_test.go	Adds structured import vs intent-expand parity tests for union validation.
pkg/tree/ops/validation/validation_expand_union_ingress_matrix_test.go	Adds a broader ingress matrix across constraint families and owners.
pkg/tree/ops/validation/validation_entry_range.go	Uses effective (matched) type for leaf range validation.
pkg/tree/ops/validation/validation_entry_pattern.go	Uses effective (matched) type for pattern validation.
pkg/tree/ops/validation/validation_entry_pattern_test.go	Adds pattern validation tests including union branches.
pkg/tree/ops/validation/validation_entry_length.go	Uses effective (matched) type for length validation.
pkg/tree/ops/validation/validation_entry_length_test.go	Adds length validation tests including union branches.
pkg/tree/ops/validation/validation_entry_leafref.go	Resolves leafref paths via effective (matched) type for union leafref branches.
pkg/tree/ops/validation/validation_dispatch.go	Adds shared helpers (effectiveFieldType, resolveLeafref) for validators.
pkg/tree/ops/validation/navigate_leafref_union_internal_test.go	Ensures internal leafref navigation works for union-matched leafref branches.
pkg/tree/ops/default_value.go	Parses union defaults with matched-member attribution for later validation.
pkg/tree/ops/default_value_test.go	Adds test ensuring union default values attach matched member type.
pkg/tree/importer/xml/xml_tree_importer.go	Returns matched union member type from XML parsing (TVFromStringWithType).
pkg/tree/importer/xml/xml_tree_importer_test.go	Tests matched-type selection, including RFC first-member behavior.
pkg/tree/importer/union_member.go	Adds union-member inference for proto-imported TypedValues.
pkg/tree/importer/union_member_test.go	Tests union-member inference RFC first-member selection behavior.
pkg/tree/importer/proto/proto_tree_importer.go	Infers and returns matched union member type on proto import.
pkg/tree/importer/proto/proto_tree_importer_test.go	Adds proto importer matched-type inference test.
pkg/tree/importer/json/json_tree_importer.go	Returns matched union member type from JSON conversion.
pkg/tree/importer/json/json_tree_importer_test.go	Extends JSON importer tests to assert matched-type behavior for union.
pkg/tree/importer/import_config_adapter.go	Extends adapter contract to return matched union member type.
go.mod	Adds replace pin for sdc-protos to get union helper APIs.
go.sum	Updates sums for the pinned sdc-protos version.

Comments suppressed due to low confidence (1)

pkg/tree/ops/validation/validation_entry_length.go:29

• Length constraints with multiple allowed intervals should pass if the value is within any interval. The current loop reports an error for every interval that doesn’t match, and can even fail when a later interval matches (e.g. length "1..3 | 10..12"). Consider checking all intervals first and emitting a single error only if none match.

		for _, lengthDef := range effectiveType.GetLength() {

			if lengthDef.Min.Value <= uint64(actualLength) && uint64(actualLength) <= lengthDef.Max.Value {
				// continue if the length is within the range
				continue

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[codecov]

Codecov Report

❌ Patch coverage is 47.20812% with 104 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
pkg/tree/importer/union_member.go	16.17%	54 Missing and 3 partials ⚠️
pkg/utils/converter.go	31.42%	24 Missing ⚠️
pkg/utils/testhelper/testhelpers.go	0.00%	7 Missing ⚠️
pkg/tree/ops/validation/validation_dispatch.go	60.00%	3 Missing and 3 partials ⚠️
pkg/tree/types/update.go	75.00%	5 Missing ⚠️
...kg/tree/ops/validation/validation_entry_leafref.go	71.42%	2 Missing and 2 partials ⚠️
pkg/tree/importer/proto/proto_tree_importer.go	80.00%	1 Missing ⚠️

📢 Thoughts on this report? Let us know!

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.