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GHC 10.0.0.20260917 · lts/ghc-10.0.x · 8c2f8e8 · 2026-10-19

Modulehakyll-4.17.0.0Haskell2010

Hakyll.Core.Identifier

An identifier is a type used to uniquely name an item. An identifier is similar to a file path, but can contain additional details (e.g. item's version). Examples of identifiers are:

  • posts/foo.markdown
  • index
  • error/404

See Identifier for details.

  • 1 type
  • 4 values
  • Packagehakyll-4.17.0.0
  • Exports5
  • LanguageHaskell2010
  • LicenceBSD-3-Clause
  • SourceIdentifier.hs
datadata Identifier
#

A key data type to identify a compiled Item in the Store. Conceptually, it's a combination of a file path and a version name. The version is used only when a file is compiled within a rule using the version wrapper function (the same source file can be compiled into several items in the store, so the version exists to distinguish them). Use functions like fromFilePath, setVersion, getMatches to build an Identifier.

Usage Examples

Normally, compiled items are saved to the store by Hakyll.Core.Rules.Rules with an automatic, implicit identifier and loaded from the store by the user in another rule with a manual, explicit identifier.

Identifiers when using match. Using match builds an implicit identifier that corresponds to the expanded, relative path of the source file on disk (relative to the project directory configured with providerDirectory):

-- e.g. file on disk: 'posts/hakyll.md'
match "posts/*" $ do                                          -- saved with implicit identifier 'posts/hakyll.md'
    compile pandocCompiler

match "about/*" $ do
    compile $ do
        compiledPost <- load (fromFilePath "posts/hakyll.md") -- load with explicit identifier
        ...

Normally, the identifier is only explicitly created to pass to one of the load functions.

Identifiers when using create. Using create (thereby inventing a file path with no underlying file on disk) builds an implicit identifier that corresponds to the invented file path:

create ["index.html"] $ do                                -- saved with implicit identifier index.html
    compile $ makeItem ("Hello world" :: String)

match "about/*" $ do
    compile $ do
        compiledIndex <- load (fromFilePath "index.html") -- load with an explicit identifier
        ...

Identifiers when using versions. With version the same file can be compiled into several items in the store. A version name is needed to distinguish them:

-- e.g. file on disk: 'posts/hakyll.md'
match "posts/*" $ do                              -- saved with implicit identifier ('posts/hakyll.md', no-version)
    compile pandocCompiler

match "posts/*" $ version "raw" $ do              -- saved with implicit identifier ('posts/hakyll.md', version raw)
    compile getResourceBody

match "about/*" $ do
    compile $ do
        compiledPost <- load (fromFilePath "posts/hakyll.md")                      -- load no-version version
        rawPost <- load . setVersion (Just "raw") $ fromFilePath "posts/hakyll.md" -- load version raw
    ...

Use setVersion to set (or replace) the version of an identifier like fromFilePath "posts/hakyll.md".

Instances6Eq, Ord, Show, IsString, NFData, Binary
valuefromFilePath :: FilePath -> Identifier
#

Parse an identifier from a file path string. For example,

-- e.g. file on disk: 'posts/hakyll.md'
match "posts/*" $ do                                          -- saved with implicit identifier 'posts/hakyll.md'
    compile pandocCompiler

match "about/*" $ do
    compile $ do
        compiledPost <- load (fromFilePath "posts/hakyll.md") -- load with explicit identifier
        ...
valuesetVersion :: Maybe String -> Identifier -> Identifier
#

Set or override the version of an identifier in order to specify which version of an Item to load from the Store. For example,

match "posts/*" $ version "raw" $ do              -- saved with implicit identifier ('posts/hakyll.md', version raw)
    compile getResourceBody

match "about/*" $ do
    compile $ do
        rawPost <- load . setVersion (Just "raw") $ fromFilePath "posts/hakyll.md" -- load version raw
        ...