The coverage manifest claimed Tagged.Mapping and Tagged.Node validate key
uniqueness, but the tagged validator's only default check was the built-in
tag check: the claim was false. Tagged.Mapping keeps every parsed pair, so a
duplicate key survives into the tree and is as invalid as in the plain model.
Add Tagged.BuiltinCheck.mappingKeysAreUnique, a Check<Mapping, Node> on the
one validation framework, to the tagged validator's defaults; the traversal
now offers each mapping to the checks. It reports each duplicate at its key
path, with failing, near-miss, and nested fixtures, and the two default
tagged checks are pinned by description.
Correct the Model.Value coverage reason: merges and aliases resolve at parse
time, so they are not a validation-phase invariant. Every validated manifest
entry now names an invariant a check actually enforces. 403 tests pass.
A Rule was exactly a Check<Model.Value, Model.Value>: it fired on every
node, switched on the value itself, and carried the root. It was therefore a
second copy of the one check machinery, the duplication the validation idiom
exists to prevent (principle 10), now also resolved for the tagged layer.
Remove Rule and its Context. The model validator holds only checks; its
default is the type-directed BuiltinCheck.mappingKeysAreUnique; validating
takes a Check. Custom whole-tree rules become Check<Model.Value, Model.Value>
with the former context.root now context.document.
Behaviour is byte-identical: the mapping-key builtin reports the same issues
at the same paths in the same DFS order, so the public validate/collect/blank
surface is unchanged. All 399 tests pass; the coverage gate reconciles to 60
public types.
The tagged-node validator carried its own copy of the validation machinery:
a Tagged.Rule cloning Validation's check type and a Tagged.Context cloning
its context, differing only in subject type. That is the per-layer
duplication the validation idiom exists to prevent (principle 10).
Generalise the type-directed framework over both the subject and the
document: SubjectContext, Check, and AnyCheck now take a Document type
parameter for the validated tree's root. The model layer validates with a
Model.Value document, the tagged layer with a Tagged.Node document, each
truthful rather than forcing one root type to stand in for the other.
The tagged layer keeps only what is genuinely its own: the Node document
type, its built-in check (now Tagged.BuiltinCheck, a Check<Node, Node>), and
its traversal. Tagged.Rule and the tagged Context are removed. The validator
surface is unchanged but validating now takes a Check<Node, Node>.
All 399 tests pass; the coverage gate reconciles to 62 public types.
Add the declarative combinators the validation idiom composes rules from,
as free functions returning closures: comparison operators (==, !=, <, <=,
>, >=) lifting a key path and a literal into a predicate; take to dig to a
value and run arbitrary logic; all to apply many checks to one context; lift
to run child-typed checks against a value reached by key path; and && / ||
to compose two checks (concatenating their errors, or short-circuiting so
errors surface only when both fail). Both the context-rooted and
subject-rooted key-path forms are provided so an author can pin the subject
type in either clause.
A key path is immutable and read-safe but not declared Sendable, so a
@Sendable predicate captures it through a small @unchecked Sendable box.
lookup is omitted: it resolves references against a component store the
generic model does not carry; a consumer with references supplies it.
Each combinator has a pure-function test against a hand-built context, per
the idiom's requirement to unit test the operators in isolation.
Introduce the core of the validation-rules idiom: a Check<Subject> with a
positive description, a when predicate, and a Bool or multi-error check
that fires only on values of its Subject type wherever they occur. AnyCheck
erases the subject and dispatches by runtime type, guarding an optional or
a wrong type from matching. The validator gains a checks list, a
validating(_:) overload, and a traversal that offers each node the values
it may specialise on. BuiltinCheck.mappingKeysAreUnique is the
type-directed counterpart of the legacy rule.
The machinery has its own negative tests (wrong type, optional, false
predicate yield nothing; same type twice yields two errors) and the builtin
ships a failing and a near-miss test. The coverage gate catches the five
new public types, which are classified as validation machinery. The default
validator is unchanged, so this is additive; retiring the legacy Rule,
moving the default onto the check, the combinator algebra, the error
rendering, and de-duplicating the Tagged validator are the remaining steps.
Move the validator toward the validation-rules idiom's identity-based
configuration. withoutValidating(_:) removes a rule by its description, the
removal identity the idiom uses, so descriptions must be unique and stable.
validationDescriptions lists the active rules in application order.
A configuration-pin test asserts the exact descriptions of the blank and
default validators and that the default descriptions are unique, so adding,
removing, or rewording a rule is a deliberate change that a test catches.
Both additions are non-breaking; the type-directed Validation<Subject>
dispatch and the error-rendering change remain the larger migration steps.
Split the six files that declared multiple sibling types under one
namespace extension so each file declares exactly one top-level type:
the Tagged node component types (Node, NodeKind, Scalar, Sequence,
Mapping, Pair), the validation report types (Report, Source,
SourceReport, BatchReport), DiagnosticKind, TokenKind, ScannerFlowContext
kind, and the event-stream composer helpers. Public type names are
unchanged; the shared report-rendering helpers move from file-private to
internal so the split report types still reach them.
Make check-namespacing.sh namespace-aware: the previous column-anchored
scan was blind to types declared inside indented extension blocks, so it
passed while the rule was violated. It now counts direct members of a
PureYAML namespace extension and ignores nested types and private helpers.
Add structured validation diagnostics, JSON and Yams comparison gates, and lazy token/event parsing so production behavior is measured without retaining full intermediate parser arrays.
