rustfmt.toml

# =============================================================================
# RUSTFMT CONFIGURATION
# =============================================================================
# This configuration defines a vertical, declarative, and diff-friendly
# coding style. It prioritizes scannability for complex builder patterns
# and minimizes "git noise" during refactors.
# =============================================================================

# -----------------------------------------------------------------------------
# CORE ENGINE & VERSIONING
# -----------------------------------------------------------------------------

# Use the 2024 Style Edition to leverage modern formatting logic.
# Requires a Nightly toolchain.
unstable_features = true
style_edition = "2024"
edition = "2024"

# -----------------------------------------------------------------------------
# LAYOUT & INDENTATION
# -----------------------------------------------------------------------------

# Prefer "Block" indentation over "Visual" alignment.
# This prevents code from drifting toward the right margin when nested
# and ensures consistent 4-space indentation regardless of identifier length.
indent_style = "Block"

# Forces multi-argument functions, closures, and calls into a "Tall" layout.
# This is specifically optimized for complex error constructors and
# command-dispatch systems where horizontal density inhibits scan-ability.
fn_params_layout = "Tall"

# -----------------------------------------------------------------------------
# STRUCTS & MATCH ARMS
# -----------------------------------------------------------------------------

# Keep structured literals vertical.
# Prevents rustfmt from collapsing structs into single-liners, preserving
# intentional whitespace for data-heavy definitions.
struct_lit_single_line = false

# Disable field alignment columns.
# A threshold of 0 prevents massive diffs when a single field name length changes,
# ensuring that refactors only affect the lines actually being modified.
struct_field_align_threshold = 0

# Ensure match arms remain diff-friendly.
# This makes moving or adding match arms cleaner in version control.
match_block_trailing_comma = true

# -----------------------------------------------------------------------------
# BUILDER PATTERNS (ARIADNE / MIETTE)
# -----------------------------------------------------------------------------

# Optimize for "Fluent" API chains.
# Allows delimited expressions (like .with_message()) to overflow onto
# new lines, which is essential for readable diagnostic and UI builders.
overflow_delimited_expr = true

# -----------------------------------------------------------------------------
# IMPORT MANAGEMENT
# -----------------------------------------------------------------------------

# Consolidate imports at the crate level.
# Balances density and organization by grouping sub-modules under the crate root.
imports_granularity = "Crate"

# Group imports by category: Standard Library -> External Crates -> Local.
group_imports = "StdExternalCrate"

# -----------------------------------------------------------------------------
# DOCUMENTATION & COMMENTS
# -----------------------------------------------------------------------------

# Ensure comments stay within the readable viewport.
# This prevents documentation drift on ultra-wide monitors.
wrap_comments = true
comment_width = 100