Rust library for converting between string cases.

use convert_case::ccase;

assert_eq!(
    ccase!(camel, "My_Var_Name"),
    "myVarName",
);
assert_eq!(
    ccase!(snake, "IOStream"),
    "io_stream",
);
assert_eq!(
    ccase!(snake -> title, "2020-04-16_family_photo"),
    "2020-04-16 Family Photo",
);

convert-case is highly customizable. You can read the API documentation on docs.rs for a list of all features and read lots of examples.

This is list of cases that convert_case provides out of the box. You can always make your own custom case.

Some cases and utilities that didn't feel appropriate in this library are made available in a distinct crate called convert_case_extras. This crate is a demonstration of what can be built on top of the convert_case API.

The command line utility ccase was made to expose the tools of the convert_case library to the command line.

$ ccase -t title super_mario_64
Super Mario 64

$ ccase -f snake -t title 2020-04-15_my_cat
2020-04-16 My Cat

$ ccase -t camel "convert to camel"
convertToCamel

The headline change permits trailing, leading, and duplicate delimiters to persist (default) or be removed. Instead of applying a single pattern, Converter supports multiple patterns and will apply them in order. This comes with another pattern Pattern::RemoveEmpty that drops empty words. This allows for opting into what was default behavior in 0.8.0 and before.

New features:

• Converter now supports multiple patterns via Converter.patterns: Vec<Pattern>. Patterns are applied in sequence, allowing for composition.
• Pattern::RemoveEmpty filters out empty words. This is useful when splitting produces empty words from leading, trailing, or duplicate delimiters (e.g., "--a--b" split on hyphens).
• Casing::remove_empty() is a convenience method that adds Pattern::RemoveEmpty to the patterns vector.

"--leading-delims".remove_empty().to_case(Case::Camel)
// "leadingDelims"

Breaking changes:

• delim_boundary macro is now separator
• Removed Casing::is_case. Similar functionality is now implemented in convert-case-extras.
• Instances of delim have been renamed to delimiter:
  • Converter.delim -> Converter.delimiter
  • Converter::set_delim -> Converter::set_delimiter
  • Case::Custom.delim -> Case::Custom.delimiter
  • Case::delim -> Case::delimiter
• Converter.pattern is now Converter.patterns with type Vec<Pattern>
  • New pattern methods on Converter just like boundaries: set_patterns, add_pattern, add_patterns, remove_pattern, remove_patterns.
  • Pattern::Noop removed. An empty patterns vector represents no mutation.
• Boundary::Custom and Pattern::Custom variants are no longer comparable.
  • Implementations of PartialEq, Eq, and Hash are no longer derived on Boundary and Pattern, and have been manually implemented.
  • Custom variants always return false for equality checks because function pointers cannot be reliably compared. This has been true for all of rust, but the compiler warning is relatively new to the author. This means remove_boundary and remove_pattern will not work for custom variants.
  • Further, all Custom variants now hash to the same value.

Other changes:

• Much improved documentation: fixed typos, better examples.
• More comprehensive testing using rstest.

Since the library is so extensible with its new API, there is no longer a need for some niche or fun transformations to be made available in this library. Some of the features that are removed are now in a new library convert_case_extras. That library will have a lower threshold on what is included (i.e. more features), and will also serve as a demonstration of what's capable with the convert_case API.

Removed:

• Case::Toggle and Pattern::Toggle
• Case::Alternating and Pattern::Alternating
• Case::Random and Pattern::Random
• Case::PseudoRandom and Pattern::PseudoRandom
• random feature is removed. The library no longer has any features.
• Case::deterministic_cases is removed
• Case::random_cases is removed

Other breaking changes:

• Boundary::Custom has lost the arg parameter and Boundary::Custom.condition is more simply fn(&[&str]) -> bool.
  • arg was originally used for building boundaries from delimiters with the Boundary::from_delim function, which is also removed because
  • delim_boundary! macro has replaced Boundary::from_delim functionality, without the need of the arg parameters
• Casing::with_boundaries is now Casing::set_boundaries and Casing::without_boundaries is now Casing::remove_boundaries to align with Converter

This release is trying to finalize the API for a 1.0.0 release. In hindsight, making Pattern a function and Boundary a struct were poor decisions. While trying to add customized behavior, I made it harder to use. Luckily, by following the convention that was done with Case in 0.8.0, which was providing a struct-variant Case::Custom, I can keep the new customization options while reverting back to the enum pattern the library has had since the beginning.

If you are updating from before 0.7.0, I don't think any changes are necessary. If you're coming from 0.7.0 or higher,

• Change boundaries from constants to enum variants: Boundary::UPPER_SNAKE into Boundary::UpperSnake
• Change patterns from functions to enum variants on Pattern: pattern::lowercase into Pattern::Lowercase

Most excitingly, I've introduced a brand new way to use the crate for 99% of use cases, which is the default behavior out of the box to just convert a string to a case, with no modifications to behavior. Instead of

use convert_case::{Case, Casing};
"MyVarName".to_case(Case::Snake);
"my-var name".from_case(Case::Title).to_case(Case::Snake);

You can use the ccase! macro:

use convert_case::ccase;
ccase!(snake, "MyVarName");
ccase!(title -> snake, "my-var name");

This means only one import and its invocation is brief and easy to read. This is now the first thing you see when viewing the docs, which themselves have gotten a huge overhaul and many improvements in this version.

New features:

• ccase! macro that performs case conversion on a string without needing to import Case or Casing. It has two forms:
  • ccase!(snake, "string") is equivalent to "string".to_case(Case::Snake)
  • ccase!(kebab -> snake, "string") is equivalent to "string".from_case(Case::Kebab).to_case(Case::Snake)
• While not intended to be used directly, the new case! macro returns a Case variant from the snake case version of the variant. For instance, case!(snake) is substituted for Case::Snake and case!(upper_flat) for Case::UpperFlat.

Other breaking changes:

• Leading, trailing, and duplicate delimiters are no longer removed and are returned as is.
• Boundary is reverted back to being an enum, but with a Custom variant that gives all the same flexibility that Boundary had as a struct. This aligns with the Case::Custom pattern.
  • Boundary.match will return true if a set of graphemes matches the boundary condition
  • Boundary methods for start and len describe how enum variants consume letters when matched
• Pattern is reverted back to being an enum, but with a Custom variant that allowed you to pass your own fn (&[&str]) -> Vec<String> as input.
  • Pattern.mutate will perform the associated mutation function
• Converter.with_boundaries has been renamed to Converter.set_boundaries.
• Removed Converter.remove_delim and Converter.remove_pattern. You can use set_delim("") and set_pattern(Pattern::Noop) instead.
• ToString is no longer a required trait for using is_case
• word_pattern module has been removed

Pattern is no longer an enum. It is now a type alias for fn(&[&str]) -> Vec<String>. The variants of Pattern can now be referenced as functions inside the pattern module. For upgrading this means changing Pattern::Lowercase to pattern::lowercase, and calling the function directly instead of invoking the mutate method on the enum.

Inside the pattern module is also the type alias Pattern itself.

Other breaking changes:

• Add Case::Ada (capital pattern with underscore delimiter.)
• Add Case::Custom variant. It is a struct variant that takes three parameters:
  • pattern with type Pattern
  • delim with type &static str, and
  • boundaries with type &'static [Boundary].
• Because of the new pattern::noop function, Converter attribute pattern is now of type Pattern and not Option<Pattern>
• Case::deterministic_cases, Case::all_cases, and Case::random_cases now return static arrays instead of vecs

Other changes:

• Added Case::split, Case::mutate, and Case::join which expose operations related to the boundaries, pattern, and delimiter of a case
• Is now no_std compatible

• Removed debug print statement.

Boundary is no longer an enum. It now is a struct, and each enum variant corresponds to an associated constant. For upgrading this just means changing Boundary::LowerUpper to just Boundary::LOWER_UPPER.

The benefit of this is that you can make your boundary conditions now, by instantiating the Boundary struct, or using Boundary::from_delim(). Now you can split on newlines, periods, double-colons, emojis, or a more complex case like a symbol followed by a digit. You also define which characters, if any, are removed during segmentation, and where the split happens.

Changes from this feature:

• Previous Boundary::PascalName enum variants now much referred to as Boundary::CONSTANT_NAME constants.
• All functions that returned groups of boundaries (such as Boundary::defaults(), Boundary::digit_letter(), etc) now are const and return fixed-sized arrays [Boundary; N], not Vec<Boundary>.
• Boundary::all() was removed, since there's no longer a sense of "all" boundaries, since you can create your own.
• Boundary::list_from() has been renamed to Boundary::defaults_from() and no longer outputs Boundary::UPPER_LOWER, since this function now only checks default boundaries.
• Create custom delimiter boundaries using Boundary::from_delim().

Other breaking changes:

• Rename Case::ScreamingSnake to Case::Constant.
• Add Case::Sentence (sentence pattern and space delimiter.)
• Casing trait implemented for Arc<str> and Rc<str> again.

Other changes:

• Remove most imports from doc comments.
• Remove loop over str::chars in favor of graphemes from unicode-segmentation.