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Formatting Differences

cfv aims to produce the same output as prettier (for JSON, JSONC, YAML) and taplo (for TOML) given equivalent settings. In most cases it does. This page documents the known differences.

These are edge cases that rarely appear in real configuration files. Across 12 real-world repositories (ansible, argo-cd, compose, hugo, next.js, poetry, prettier, react, ripgrep, rust-analyzer, uv, vscode), cfv matches the reference tools on 99%+ of files.

YAML​

Multiline plain scalar reflow​

When a plain scalar (unquoted string) wraps across multiple lines and exceeds the print width, prettier moves the value to the next line and re-wraps at tabWidth indent. cfv preserves the original line breaks.

prettier:

description:
  The item and key options control which entries
  are handled. Default may change in future releases.

cfv:

description: The item and key options control which entries
  are handled. Default may change in future releases.

Affects long descriptions in Ansible modules and similar files. Safe divergence: the YAML parses identically either way.

Explicit key style​

YAML allows explicit keys with ?. Prettier simplifies ? key to key: when possible. cfv preserves the explicit style.

prettier:

key: value

cfv:

? key
: value

This is a style choice. Both are valid YAML and parse identically.

Anchor and tag ordering​

For nodes with both an anchor and a tag, YAML allows either order. Prettier normalizes to tag-first (!!str &anchor). cfv preserves the source order.

prettier:

!!str &name value

cfv:

&name !!str value

Both are valid per the YAML spec. The parsed result is identical.

JSON / JSONC​

Block comments inside inline objects​

When an inline object contains a block comment before a key, prettier keeps it on one line. cfv expands to multiline.

prettier:

{ /*comment*/ "key": "value" }

cfv:

{
  /*comment*/
  "key": "value"
}

This only affects JSONC (JSON doesn't have comments). The parsed result is identical.

TOML​

Unsupported taplo options​

cfv reads most taplo formatting options but does not support:

  • align_entries (align = signs across keys)
  • align_comments (align inline comments)
  • compact_arrays / compact_inline_tables (force single-line)
  • array_auto_expand / array_auto_collapse (custom width thresholds)
  • [[rule]] sections (per-path overrides)

If your taplo.toml relies on these, cfv output may differ from taplo fmt for those specific behaviors. cfv uses its own defaults (expand/collapse at column width 80, no entry alignment).

General​

Leading blank lines​

prettier and taplo both preserve leading blank lines at the start of a file. cfv strips them. This affects no real-world config files in practice.

.prettierrc.js and overrides​

cfv cannot read JavaScript-based prettier configs (.prettierrc.js, .prettierrc.cjs, prettier.config.js) because they require a JS runtime. If your project uses one of these, cfv falls back to .editorconfig or defaults.

The prettier overrides array is also not supported. Only top-level options apply.