jsony_macros 0.1.10

// Initially From serde: https://github.com/serde-rs/serde/blob/master/serde_derive/src/internals/case.rs
// Code to convert the Rust-styled field/variant (e.g. `my_field`, `MyType`) to the
// case of the source (e.g. `my-field`, `MY_FIELD`).
use proc_macro::Literal;

use crate::Error;

use self::RenameRule::*;
use std::fmt::{self, Debug, Display};

/// The different possible ways to change case of fields in a struct, or variants in an enum.
#[derive(Copy, Clone, PartialEq)]
pub enum RenameRule {
    /// Don't apply a default rename rule.
    None,
    /// Rename direct children to "lowercase" style.
    LowerCase,
    /// Rename direct children to "UPPERCASE" style.
    UpperCase,
    /// Rename direct children to "PascalCase" style, as typically used for
    /// enum variants.
    PascalCase,
    /// Rename direct children to "camelCase" style.
    CamelCase,
    /// Rename direct children to "snake_case" style, as commonly used for
    /// fields.
    SnakeCase,
    /// Rename direct children to "SCREAMING_SNAKE_CASE" style, as commonly
    /// used for constants.
    ScreamingSnakeCase,
    /// Rename direct children to "kebab-case" style.
    KebabCase,
    /// Rename direct children to "SCREAMING-KEBAB-CASE" style.
    ScreamingKebabCase,
}

static RENAME_RULES: &[(&str, RenameRule)] = &[
    ("\"lowercase\"", LowerCase),
    ("\"UPPERCASE\"", UpperCase),
    ("\"PascalCase\"", PascalCase),
    ("\"camelCase\"", CamelCase),
    ("\"snake_case\"", SnakeCase),
    ("\"SCREAMING_SNAKE_CASE\"", ScreamingSnakeCase),
    ("\"kebab-case\"", KebabCase),
    ("\"SCREAMING-KEBAB-CASE\"", ScreamingKebabCase),
];
fn underscores_to_hyphens(mut s: String) -> String {
    // SAFETY: replacing '_' (0x5F) with '-' (0x2D) preserves valid UTF-8
    unsafe {
        for b in s.as_bytes_mut() {
            if *b == b'_' {
                *b = b'-';
            }
        }
    }
    s
}

impl RenameRule {
    pub fn from_literal(ident: &Literal) -> Self {
        let lit = ident.to_string();
        for (name, rule) in RENAME_RULES {
            if lit == *name {
                return *rule;
            }
        }
        Error::span_msg_ctx("", &ParseError { unknown: &lit }, ident.span())
    }

    /// Apply a renaming rule to an enum variant, returning the version expected in the source.
    pub fn apply_to_variant(self, variant: &str) -> String {
        match self {
            None | PascalCase => variant.to_owned(),
            LowerCase => variant.to_ascii_lowercase(),
            UpperCase => variant.to_ascii_uppercase(),
            CamelCase => variant[..1].to_ascii_lowercase() + &variant[1..],
            SnakeCase => {
                let mut snake = String::new();
                for (i, ch) in variant.char_indices() {
                    if i > 0 && ch.is_uppercase() {
                        snake.push('_');
                    }
                    snake.push(ch.to_ascii_lowercase());
                }
                snake
            }
            ScreamingSnakeCase => SnakeCase.apply_to_variant(variant).to_ascii_uppercase(),
            KebabCase => underscores_to_hyphens(SnakeCase.apply_to_variant(variant)),
            ScreamingKebabCase => {
                underscores_to_hyphens(ScreamingSnakeCase.apply_to_variant(variant))
            }
        }
    }

    /// Apply a renaming rule to a struct field, returning the version expected in the source.
    pub fn apply_to_field(self, field: &str) -> String {
        match self {
            None | LowerCase | SnakeCase => field.to_owned(),
            UpperCase => field.to_ascii_uppercase(),
            PascalCase => {
                let mut pascal = String::new();
                let mut capitalize = true;
                for ch in field.chars() {
                    if ch == '_' {
                        capitalize = true;
                    } else if capitalize {
                        pascal.push(ch.to_ascii_uppercase());
                        capitalize = false;
                    } else {
                        pascal.push(ch);
                    }
                }
                pascal
            }
            CamelCase => {
                let pascal = PascalCase.apply_to_field(field);
                pascal[..1].to_ascii_lowercase() + &pascal[1..]
            }
            ScreamingSnakeCase => field.to_ascii_uppercase(),
            KebabCase => underscores_to_hyphens(field.into()),
            ScreamingKebabCase => {
                underscores_to_hyphens(ScreamingSnakeCase.apply_to_field(field).into())
            }
        }
    }
}

pub struct ParseError<'a> {
    unknown: &'a str,
}

impl<'a> Display for ParseError<'a> {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        f.write_str("unknown rename rule `rename_all = ")?;
        Debug::fmt(self.unknown, f)?;
        f.write_str("`, expected one of ")?;
        for (i, (name, _rule)) in RENAME_RULES.iter().enumerate() {
            if i > 0 {
                f.write_str(", ")?;
            }
            Debug::fmt(name, f)?;
        }
        Ok(())
    }
}

#[test]
fn rename_variants() {
    for &(original, lower, upper, camel, snake, screaming, kebab, screaming_kebab) in &[
        (
            "Outcome", "outcome", "OUTCOME", "outcome", "outcome", "OUTCOME", "outcome", "OUTCOME",
        ),
        (
            "VeryTasty",
            "verytasty",
            "VERYTASTY",
            "veryTasty",
            "very_tasty",
            "VERY_TASTY",
            "very-tasty",
            "VERY-TASTY",
        ),
        ("A", "a", "A", "a", "a", "A", "a", "A"),
        ("Z42", "z42", "Z42", "z42", "z42", "Z42", "z42", "Z42"),
    ] {
        assert_eq!(None.apply_to_variant(original), original);
        assert_eq!(LowerCase.apply_to_variant(original), lower);
        assert_eq!(UpperCase.apply_to_variant(original), upper);
        assert_eq!(PascalCase.apply_to_variant(original), original);
        assert_eq!(CamelCase.apply_to_variant(original), camel);
        assert_eq!(SnakeCase.apply_to_variant(original), snake);
        assert_eq!(ScreamingSnakeCase.apply_to_variant(original), screaming);
        assert_eq!(KebabCase.apply_to_variant(original), kebab);
        assert_eq!(
            ScreamingKebabCase.apply_to_variant(original),
            screaming_kebab
        );
    }
}

#[test]
fn rename_fields() {
    for &(original, upper, pascal, camel, screaming, kebab, screaming_kebab) in &[
        (
            "outcome", "OUTCOME", "Outcome", "outcome", "OUTCOME", "outcome", "OUTCOME",
        ),
        (
            "very_tasty",
            "VERY_TASTY",
            "VeryTasty",
            "veryTasty",
            "VERY_TASTY",
            "very-tasty",
            "VERY-TASTY",
        ),
        ("a", "A", "A", "a", "A", "a", "A"),
        ("z42", "Z42", "Z42", "z42", "Z42", "z42", "Z42"),
    ] {
        assert_eq!(None.apply_to_field(original), original);
        assert_eq!(UpperCase.apply_to_field(original), upper);
        assert_eq!(PascalCase.apply_to_field(original), pascal);
        assert_eq!(CamelCase.apply_to_field(original), camel);
        assert_eq!(SnakeCase.apply_to_field(original), original);
        assert_eq!(ScreamingSnakeCase.apply_to_field(original), screaming);
        assert_eq!(KebabCase.apply_to_field(original), kebab);
        assert_eq!(ScreamingKebabCase.apply_to_field(original), screaming_kebab);
    }
}