[jdx]

https://entire.io/gh/jdx/mise/trails/460

Adds mise_util::structured_merge, which sets some keys of a JSON, TOML, or YAML file and leaves the rest alone, plus contains, which reports whether a file already holds those keys. Nothing calls it yet; the merge dotfile entries stacked on top use it (#13986).

• TOML edits in place through toml_edit: comments, key order, and the formatting of untouched keys survive.
• YAML goes through the yaml_merge helper from the PR below.
• JSON keeps key order and the file's own indent, and keeps a trailing newline if there was one.
• Tables merge recursively; scalars and arrays are replaced; nothing is ever removed. An empty target is an empty table.
• contains compares parsed values and looks only at the source's keys, so a target that already satisfies the source is returned byte for byte and keys the application added are not drift.

serde_json's preserve_order feature was already enabled workspace-wide through feature unification; mise-util now asks for it explicitly. Cargo.lock does not change.

Verified with unit tests (per-format merges, idempotence, unparseable and non-table input), cargo clippy --workspace --all-features --all-targets -- -D warnings, and cargo +1.95 check.

Stacked on #14010.

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Note

Low Risk
New, unused library code with tests only—no behavior change to existing mise flows until wired in.

Overview
Adds mise_util::structured_merge so callers can patch only the keys they own in shared config files (JSON, TOML, YAML) without rewriting the rest. merge applies source keys with shared semantics (nested objects merge recursively; scalars and arrays are replaced; extra target keys are never removed), and returns the target byte-for-byte when it already matches. contains checks drift using only the source’s keys.

Format-specific writers aim to preserve hand-edited formatting: JSON uses serde_json raw_value to keep untouched value text, key order, and indent; TOML merges via toml_edit to keep comments and decorations; YAML delegates to the existing yaml_merge helper. serde_json in mise-util now explicitly enables preserve_order and raw_value. The module is exported from lib.rs and covered by unit tests; nothing in the repo calls it yet.

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Summary by CodeRabbit

• New Features
  • Added structured merging for JSON, TOML, and YAML configuration files. Merges retain keys that exist only in the target, and files that already contain all source values are left unchanged.
  • Improved preservation of existing formatting during merges, including JSON indentation and newline style and TOML value decorations.

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📥 Commits

Reviewing files that changed from the base of the PR and between 4e05f81 and 44ec1f6.

📒 Files selected for processing (2)

• crates/mise-util/Cargo.toml
• crates/mise-util/src/structured_merge.rs

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📥 Commits

Reviewing files that changed from the base of the PR and between 688eb51 and 4e05f81.

📒 Files selected for processing (3)

• crates/mise-util/Cargo.toml
• crates/mise-util/src/lib.rs
• crates/mise-util/src/structured_merge.rs

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📝 Walkthrough

Walkthrough

The change adds a public structured-merge module to mise-util. It detects JSON, TOML, and YAML formats, checks whether a target contains source values, and merges documents while retaining target-only values and selected formatting.

Changes

Structured Merge

Layer / File(s)	Summary
Format detection and containment crates/mise-util/src/lib.rs, crates/mise-util/src/structured_merge.rs	The new public module defines JSON, TOML, and YAML formats, detects formats from file extensions, parses documents, and checks whether targets contain source values. Tests cover format detection and containment behavior.
Format-specific merging and validation crates/mise-util/Cargo.toml, crates/mise-util/src/structured_merge.rs	merge returns the target unchanged when it contains the source; otherwise it merges by format. JSON output uses inferred indentation and newline handling. TOML merging retains formatting for equal values and decoration for replaced values. Tests cover merges, formatting, idempotence, and errors.

Priority: ⬇️ Low

Estimated code review effort: 3 (Moderate) | ~20 minutes

Change: Feature

Merge Risk: ⚪ Minimal · up to 4e05f

The reported merge failures are not present in this change; it is mergeable after normal checks.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 64.29% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 28 functions across 2 files. (1 skipped: …	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly summarizes the main change: adding format-aware merge support for JSON, TOML, and YAML files.

Full details: Docstring Coverage

Explanation

Docstring coverage is 64.29% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 28 functions across 2 files. (1 skipped: 1 unsupported.)

✨ Finishing Touches 💡 1

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[greptile-apps]

Confidence Score: 5/5

[Medium risk] Adds a new utility module for merging structured config files.

The PR appears safe to merge; no new blocking issue was found.

What we checked:

• Target-only JSON keys survive: Each object starts with every target entry. The merge then visits only source keys, keeping other entries as their original text.

Summary

Adds structured_merge for JSON, TOML, and YAML, with recursive table merges and checks for already-matching source keys.

• The latest changes keep untouched JSON values as their original text and extend TOML comparisons to arrays of tables.
• Both earlier, unnumbered findings are addressed: equal TOML arrays keep their comments, and unrelated JSON numbers are no longer rewritten.
• Known limitation acknowledged by jdx: huge integers in JSON source values still round because source values remain parsed as Value.
• No new actionable issues were found. Tests were inspected, not run.

_{Reviews (3) · Last reviewed commit: "fix(util): keep untouched JSON text exac..."}

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Cursor Bugbot has reviewed your changes and found 1 potential issue.

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[github-actions]

Instruction counts

Nothing was compared, and so nothing was gated. No series appears on both sides: either the base has no measurements recorded, or the two were measured on different runner classes, which are deliberately not comparable — counts shift between machine types by more than a real regression does.

New, nothing to compare against: env on jdx-perf-v1-ubuntu24.04-x64-mise-rust1.97.1-img5263c143, hook-env on jdx-perf-v1-ubuntu24.04-x64-mise-rust1.97.1-img5263c143, ls on jdx-perf-v1-ubuntu24.04-x64-mise-rust1.97.1-img5263c143, registry on jdx-perf-v1-ubuntu24.04-x64-mise-rust1.97.1-img5263c143, startup on jdx-perf-v1-ubuntu24.04-x64-mise-rust1.97.1-img5263c143

_{Only instruction counts gate. Wall clock is shown for context — on identical hardware it moves 4-20% run to run.}

_{Measured by tak — instruction-counted CLI benchmarks, stored in this repository's git notes.}

_{44ec1f6ed7f3 vs 688eb512357b · measured on the runner, not pushed to the history.}