# 9. Package Description Format Specification History

Package descriptions need to specify the version of the specification they need to be interpreted in via the `cabal-version` declaration. The following list describes changes that occurred in each version of the cabal specification relative to the respective preceding published version.

Note

The sequence of specification version numbers is not contiguous because it’s synchronised with the version of the `Cabal` library. As a consequence, only even versions are considered proper published versions of the specification as odd versions of the `Cabal` library denote unreleased development branches which have no stability guarantee.

## 9.1. `cabal-version: 3.8`

- Added field `code-generators` to `test-suite` stanzas. This enumerates executabes (possibly brought into scope by `build-tool-depends`) that are run after all other preprocessors. These executables are invoked with a target dir for output, a sequence of all source directories with source files of local lib components that the given test stanza depends on, and following a double dash, all options cabal would pass to ghc for a build. They are expected to output a newline-separated list of generated modules which have been written to the targetdir. This can be used for driving doctests and other discover-style tests generated from source code.

- Added fields `extra-libraries-static` and `extra-lib-dirs-static` to allow Haskell libraries to remember linker flags needed for fully static linking of system libraries into executables. The existing field `pkgconfig-depends` can used to append the relevant output of `pkg-config --libs --static` to these new fields automatically. When `extra-libraries-static` is not given, it defaults to `extra-libraries`. When `extra-lib-dirs-static` is not given, it defaults to `extra-lib-dirs`.

- Wildcard matching has been slightly expanded. Matches are now allowed of the form `foo/**/literalFile`. Prior, double-star wildcards required the trailing filename itself be a wildcard.

- Allow the omission of the type field in test-suite and benchmark stanzas when the type can be inferred by the presence of main-is or test-module.

- License fields use identifiers from SPDX License List version `3.16 2022-02-06`

## 9.2. `cabal-version: 3.6`

- License fields use identifiers from SPDX License List version `3.10 2020-08-03`

- Add `hsc2hs-options`

## 9.3. `cabal-version: 3.4`

- License fields use identifiers from SPDX License List version `3.9 2020-05-15`

- Dependencies to sublibraries must be specified explicitly, even for current package. For example: `build-depends: mypackage:internal-lib` This way you can have an internal library with the same name as some external dependency.

- Remove `-any` and `-none` syntax for version ranges Use `>=0` and `<0` respectively.

- `default-language` is optional. The Default value is to use the compiler’s default language.

- `mixins` field allow specifying a sublibrary.

## 9.4. `cabal-version: 3.0`

- New `library:visibility` for exposing sublibraries.

- New `pkg:lib` and `pkg:{lib1,lib2}` syntax in `build-depends` for depending on public sublibraries from other packages.

- Added the `extra-dynamic-library-flavours` field to specify non-trivial variants of dynamic flavours. It is `extra-library-flavours` but for shared libraries. Mainly useful for GHC’s RTS library.

- Free text fields (e.g. `description`) preserve empty lines and indentation. In other words, you don’t need to add dots for blank lines.

- License fields use identifiers from SPDX License List version `3.6 2019-07-10`

- Remove deprecated `hs-source-dir`, `extensions` and `build-tools` fields.

- Common stanzas are now allowed also in the beginning of conditional sections. In other words, the following is valid

  >     library
  >         import deps

  >         if flag(foo)
  >             import foo-deps

- Allow redundant leading or trailing commas in package fields with optional commas, such as `library:exposed-modules`

- Require fields with optional commas to consistently omit or place commas between elements.

- Changed the behavior of `extra-bundled-libraries` field. The naming convention of dynamic library files (e.g. generated by a custom build script) has changed. For library names prefixed with “C”, the dynamic library file name(s) must be of the form lib<library-name>.<dyn-library-extension>* instead of the old libC<library-name>-ghc<ghc-flavour><ghc-version>.<dyn-library-extension>

- New set-notation syntax for `==` and `^>=` operators, see `build-depends` field documentation for examples.

- Allow more whitespace in `mixins` field

- Wildcards are disallowed in `pkgconfig-depends`, Yet the pkgconfig format is relaxed to accept e.g. versions like `1.1.0h`.

- New `autogen-includes` for specifying `install-includes` which are autogenerated (e.g. by a `configure` script).

- New `asm-sources` and `asm-options` fields added for supporting bundled foreign routines implemented in assembler.

- New `cmm-sources` and `cmm-options` fields added for supporting bundled foreign primops implemented in C–.

## 9.5. `cabal-version: 2.4`

- Wildcard matching has been expanded. All previous wildcard expressions are still valid; some will match strictly more files than before. Specifically:

  - Double-star (`**`) wildcards are now accepted for recursive matching immediately before the final slash; they must be followed by a filename wildcard (e.g., `foo/**/*.html` is valid; `foo/**/bar/*.html` and `foo/**/**/*.html`, `foo/**/bar.html` are all invalid). As `**` was an error in globs before, this does not affect any existing `.cabal` files that previously worked. (Caveat: Double-star wildcards in `data-files` directories, e.g. `data-files: data/**/*.csv`, are only supported correctly from Cabal 3.0.)

  - Wildcards now match when the pattern’s extensions form a suffix of the candidate file’s extension, rather than requiring strict equality (e.g., previously `*.html` did not match `foo.en.html`, but now it does).

- License fields use identifiers from SPDX License List version `3.2 2018-07-10`

## 9.6. `cabal-version: 2.2`

- New `common` stanzas and `import` pseudo-field added.

- New `library:virtual-modules` field added.

- New `cxx-sources` and `cxx-options` fields added for supporting bundled foreign routines implemented in C++.

- New `extra-bundled-libraries` field for specifying additional custom library objects to be installed.

- Extended `if` control structure with support for `elif` keyword.

- Changed default rules of `build-type` field to infer “build-type:” for “Simple”/”Custom” automatically.

- `license` field syntax changed to require SPDX expression syntax (using SPDX license list version `3.0 2017-12-28`).

- Allow redundant leading or trailing commas in package fields (which require commas) such as `build-depends`.

## 9.7. `cabal-version: 2.0`

- New `library:signatures` and `mixins` fields added for supporting Backpack.

- New `build-tool-depends` field added for adding build-time dependencies of executable components.

- New `custom-setup:autogen-modules` field added for declaring modules which are generated at build time.

- Support for new PVP caret-style version operator (`^>=`) added to `build-depends`.

- Add support for new `foreign-library` stanza.

- Add support for internal library stanzas.

- New CPP Macro `CURRENT_PACKAGE_VERSION`.

## 9.8. `cabal-version: 1.24`

- New `custom-setup` stanza and `custom-setup:setup-depends` field added for specifying dependencies of custom `Setup.hs` scripts.

- CPP Macros `VERSION_$pkgname` and `MIN_VERSION_$pkgname` are now also generated for the current package.

- New CPP Macros `CURRENT_COMPONENT_ID` and `CURRENT_PACKAGE_KEY`.

- New `extra-framework-dirs` field added for specifying extra locations to find OS X frameworks.

## 9.9. `cabal-version: 1.22`

- New `library:reexported-modules` field.

- Support for `-none` version constraint added to `build-depends`.

- New `license` type `ISC` added.

## 9.10. `cabal-version: 1.20`

- Add support for new `license-files` field for declaring multiple license documents.

- New CPP Macro `MIN_TOOL_VERSION_$buildtool`.

- New `license` types `BSD2` and `MPL-2.0` added.

## 9.11. `cabal-version: 1.18`

- Add support for new `extra-doc-files` field for specifying extra file assets referenced by the Haddock documentation.

- New `license` type `AGPL` and `AGPL-3` added.

- Add support for specifying a C/C++/obj-C source file in `executable:main-is` field.

- Add `getSysconfDir` operation to `Paths_` API.

## 9.12. `cabal-version: 1.16`

Todo

this needs to be researched; there were only few changes between 1.12 and 1.18;

## 9.13. `cabal-version: 1.12`

- Change syntax of `cabal-version` to support the new recommended `cabal-version: x.y` style