Module format 

Deterministic formatting of Cove source.

The formatter prints an ast::SourceUnit back to source text. It is deterministic and idempotent: formatting twice produces exactly what formatting once produced, and re-parsing the result produces the same tree.

Layout

Two spaces of indentation, no tabs, no trailing whitespace, one trailing newline. Lines are kept within MAX_WIDTH columns where a legal break exists.

The newline rule

Cove statements end at the end of a line, so a formatter cannot break a line wherever it likes: a break in the wrong place silently splits one statement into two. Every break this module introduces is one the parser reads as a continuation — inside a (, [, or < group, immediately after a binary operator, or before a leading . — which is why long argument lists break one argument per line, a binary expression breaks after its operator, and a method chain breaks before its dots.

Comments

The tree carries /// doc comments but not // or /* */ comments, and not the blank lines an author wrote between statements. format_source reads those back out of the source text and re-attaches them by position: a comment on its own line attaches to the item or statement that follows it, and a comment at the end of a line stays at the end of that line. No comment is ever dropped; one the formatter cannot place exactly is moved to the nearest following boundary rather than lost.

Constants

MAX_WIDTH

The column the formatter keeps lines within when a legal break exists.

Functions

format_expr

Renders one expression on a single line, from the tree alone.

format_source

Formats unit, which must be the tree parsed from source.

format_unit

Formats one parsed source unit deterministically.