Support complex values (dicts/lists) in replace and upsert

[nathanjmcdougall]

Summary

• Intercept Replace operations with Mapping/Sequence values in the Rust layer before they reach yamlpatch (which can't handle multi-line serialized values)
• Perform direct string surgery: find key-colon boundary, extract inline comments, compute indentation, serialize via serde_yaml::to_string(), and reassemble
• Extract shared apply_patches_impl so both Document.apply_patches() and _core.apply_patches() handle complex values consistently

Changes

• src/document.rs: Add apply_complex_replace + 3 helpers (find_key_colon, extract_inline_comment, indent_block), extract apply_patches_impl as shared batch-flush logic
• src/ops.rs: Delegate to apply_patches_impl instead of passing everything to yamlpatch directly
• tests/test_document.py: 17 new tests (replace with dict/list, nested, comment relocation, root-level, indentation depths)
• tests/test_core_ops.py: 2 new tests for _core.apply_patches with complex values

Fixes #18

[Copilot]

Pull request overview

Adds support for complex (Mapping/Sequence) values in Document.replace() and Document.upsert(), which previously raised PatchError because yamlpatch serializes Replace values inline after the key colon. The fix intercepts complex Replace operations in the Rust layer and performs direct string surgery on the document source, while scalar Replaces and other operations still flow through yamlpatch unchanged.

Changes:

• New apply_complex_replace plus find_key_colon / extract_inline_comment / indent_block helpers in src/document.rs to handle multi-line block-style replacement with comment relocation and indentation.
• Extracted shared apply_patches_impl so both Document.apply_patches and _core.apply_patches route complex replaces through the new path; the old duplicated batch logic in src/ops.rs is removed.
• New tests (19 in tests/test_document.py, 3 in tests/test_core_ops.py) covering dict/list replaces, nesting, comment relocation, root-level replace, indentation depths, and quoted-key edge cases; README and a design doc are added.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
src/document.rs	Implements complex-value replace via string surgery and shared apply_patches_impl.
src/ops.rs	Routes apply_patches through the shared impl instead of calling yamlpatch directly.
tests/test_document.py	Adds TestDocumentReplaceComplex and TestDocumentUpsertComplex covering dict/list cases.
tests/test_core_ops.py	Adds _core.apply_patches tests for dict, list, and mixed batches.
README.md	Documents that dicts/lists are now accepted by replace/upsert.
doc/specs/2026-05-15-complex-value-replace-design.md	Design rationale, algorithm, scope, and known limitations.

Comments suppressed due to low confidence (1)

src/document.rs:377

• The single-quote handling treats every ' as a state toggle, which is correct for strict open/close but mishandles YAML's escaped single quote ('' inside a single-quoted string represents a literal '). For a string like 'it''s # ok', the toggling will close on the second quote, treat s # ok as outside the string, and incorrectly extract # ok as an inline comment. Consider treating '' while in_single_quote as an escaped quote (advance i by 2 and stay inside the string).

            b'\'' if !in_double_quote => {
                in_single_quote = !in_single_quote;
            }

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[Copilot]

Pull request overview

Copilot reviewed 6 out of 6 changed files in this pull request and generated no new comments.