fix(bundler): inline a $ref to a sequence or scalar as that kind of node

[daveshanley]

Fixes #607. Supersedes #608.

Problem

BundleBytesComposed panics with index out of range [N] with length N when a $ref resolves to an odd-length array, e.g. tags: {$ref: "tags.yaml#/tags"}.

walkAndRewriteRefs already handles sequences correctly. The corrupt node comes from the composer. When a $ref can't be lifted into components, the inline fallback (inlineProcessRef, inlineMatchingRefs, rewriteInlinedAbsoluteRefs) replaces only the $ref node's .Content with the target's .Content. The $ref node is a mapping, so a sequence target becomes a mapping node holding N sequence items:

• odd N → the walker reads Content[i+1] past the end → panic;
• even N → no panic, but a corrupted mapping is left in the index. This is why the issue saw 64 succeed and 63/65 fail.

Fix

One helper, inlineRefNode(refNode, target), used at all four Content-only sites:

• mapping target: swaps Content only, exactly as today, so the ref node keeps its own style and comments. Output for the common case is unchanged.
• any other target (sequence, scalar, alias): also adopts the target's Kind, Tag, Style, Value and Alias.

replaceRefNodeWithContent (extension refs) wasn't reused because it always copies style, anchor and comments. That would change the rendered output of ordinary mapping refs.

Why not #608

#608 adds a bounds check inside walkAndRewriteRefs. That stops the panic but leaves the corrupted mapping node in place, and once the node is built correctly the guard can never trigger.

Note: $ref'd tags are still not in the output

After this fix neither composed nor inline (BundleBytes) bundling crashes, but neither emits tags for tags: {$ref: ...}. This was already true for inline bundling on main. The bundlers render from the model, and extractTags (datamodel/low/v3/create_document.go) only accepts a sequence node. OpenAPI 3.x does not allow a Reference Object for tags, so the model ignores it. Supporting it would mean resolving the ref in extractTags, while keeping the original key/value nodes so tags still renders in its original position. That's a separate decision, so it's not in this PR.

Tests

bundler/issue607_test.go:

• TestBundleBytesComposed_Issue607_SequenceRefDoesNotPanic: 1, 2, 3, 63, 64 and 65 tags. The odd counts panic on main.
• TestBundleDocumentComposed_Issue607_InlinedSequenceRefBecomesSequence: after composing, the root tags node is a real !!seq with the three tags. An operation-level tags: {$ref: ...} flow list renders as [a, b, c].
• TestInlineRefNode_Issue607: sequence, scalar, alias and mapping targets. The mapping case keeps its kind, tag, flow style and head comment.

bundler coverage: 100%. ./tests and the root package pass.

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (61ea631) to head (9fa9a3e).

Additional details and impacted files

@@            Coverage Diff            @@
##              main      #637   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files          297       297           
  Lines        37662     37671    +9     
=========================================
+ Hits         37662     37671    +9     

Flag	Coverage Δ
unittests	100.00% <100.00%> (ø)

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