Formatter.Logical.LiteralFormat

Source-text formatting of primitive literals: strings, chars, and hex integers. Pure string-to-string conversions; no LPT awareness.

This module is exposed only so that the unit tests can reach it — tests/ is a separate application that depends on this package, so it can import nothing that is not in exposed-modules. An application using the formatter has no reason to call these; it goes through Formatter.prettyPrint, which applies them for you.

escapeStringContent : String -> String

Escape content for embedding in a single-quoted "..." literal: tab, newline, carriage return, " and \ become their two-character escapes, and every other code point goes through escapeUnlessPrintable — verbatim if it is printable, a \u{HEX} escape if it is not.
escapeMultilineContent : String -> String

Escape content for embedding in a triple-quoted """...""" literal. These strings still process \ as an escape introducer, so literal backslashes must be doubled or the parser will misinterpret the next character (e.g. \. is rejected as "invalid escape sequence"). But newlines and tabs are preserved as themselves — the whole point of """ is that real newlines stand for newlines.

A double quote only needs escaping when it is part of a run of three or more (which would terminate the literal, or embed a stray """). An isolated " (or a run of one or two mid-content) is left verbatim. This mirrors elm-format's escapeMultiQuote: an isolated quote in an embedded template or fixture (e.g. Debug.log "u") is preserved as-is rather than backslash-escaped.
charLiteralString : Char -> String

The source text of a character literal, quotes included: 'a', '\n', '\u{FEFF}'. Tab, newline, carriage return, ' and \ take their two-character escapes; every other code point goes through escapeUnlessPrintable, exactly as a string's does — so 'é' is a letter and '\u{FEFF}' keeps its escape.
hexLiteral : Int -> String

The source text of a hex integer literal, sign included: 0x1F, or -0x1.

A negative can reach here: the parser folds a leading - into the value it stores (Src.PInt { value = -1, isHex = True }), so the sign is placed in front of the 0x rather than left to the digits.
intToHex : Int -> String

The hex digits of n, uppercase and unpadded. Callers building a literal want hexLiteral, which places the 0x after the sign; a negative reaching here still gets a - rather than a wrong digit.