hakyll-4.16.4.0: A static website compiler library
Safe HaskellSafe-Inferred
LanguageHaskell2010

Hakyll.Web.Template.Context

Description

This module provides Contexts which are used to expand expressions in templates and allow for arbitrary customisation.

Templates define a small expression DSL which consists of strings, identifiers and function application. There is no type system, every value is a string and on the top level they get substituted verbatim into the page.

For example, you can build a context that contains

… <> functionField "concat" (const . concat) <> …

which will allow you to use the concat identifier as a function that takes arbitrarily many strings and concatenates them to a new string:

$partial(concat("templates/categories/", category))$

This will evaluate the category field in the context, then prepend the path, and include the referenced file as a template.

Synopsis

Documentation

data ContextField Source #

Mostly for internal usage

Constructors

EmptyField 
StringField String 
forall a. ListField (Context a) [Item a] 

newtype Context a Source #

The Context monoid. Please note that the order in which you compose the items is important. For example in

field "A" f1 <> field "A" f2

the first context will overwrite the second. This is especially important when something is being composed with metadataField (or defaultContext). If you want your context to be overwritten by the metadata fields, compose it from the right:

metadataField <> field "date" fDate

Constructors

Context 

Instances

Instances details
Monoid (Context a) Source # 
Instance details

Defined in Hakyll.Web.Template.Context

Methods

mempty :: Context a #

mappend :: Context a -> Context a -> Context a #

mconcat :: [Context a] -> Context a #

Semigroup (Context a) Source #

Tries to find a key in the left context, or when that fails in the right context.

Instance details

Defined in Hakyll.Web.Template.Context

Methods

(<>) :: Context a -> Context a -> Context a #

sconcat :: NonEmpty (Context a) -> Context a #

stimes :: Integral b => b -> Context a -> Context a #

field Source #

Arguments

:: String

Key

-> (Item a -> Compiler String)

Function that constructs a value based on the item (e.g. accessing metadata)

-> Context a 

Constructs a new field for a Context. If the key matches, the compiler is run and its result is substituted in the template.

If the compiler fails, the field will be considered non-existent in an $if()$ macro or ultimately break the template application (unless the key is found in another context when using <>). Use empty or noResult for intentional failures of fields used in $if()$, to distinguish them from exceptions thrown with fail.

boolField Source #

Arguments

:: String

Key

-> (Item a -> Bool)

Extract value from an Item a

-> Context a 

Creates a field to use with the $if()$ template macro. Attempting to substitute the field into the template will cause an error.

boolFieldM Source #

Arguments

:: String

Key

-> (Item a -> Compiler Bool)

Extract value from an Item a from within the Compiler monad

-> Context a 

Creates a field to use with the $if()$ template macro, in the Compiler monad. Attempting to substitute the field into the template will cause an error.

Since: 4.16.4.0

constField Source #

Arguments

:: String

Key

-> String

Value

-> Context a 

Creates a field that does not depend on the Item but always yields the same string

listField :: String -> Context a -> Compiler [Item a] -> Context b Source #

Creates a list field to be consumed by a $for(…)$ expression. The compiler returns multiple items which are rendered in the loop body with the supplied context.

listFieldWith :: String -> Context a -> (Item b -> Compiler [Item a]) -> Context b Source #

Creates a list field like listField, but supplies the current page to the compiler.

functionField Source #

Arguments

:: String

Key

-> ([String] -> Item a -> Compiler String)

Function

-> Context a 

Creates a variadic function field.

The function will be called with the dynamically evaluated string arguments from the template as well as the page that is currently rendered.

mapContext :: (String -> String) -> Context a -> Context a Source #

Transform the respective string results of all fields in a context. For example,

mapContext (++"c") (constField "x" "a" <> constField "y" "b")

is equivalent to

constField "x" "ac" <> constField "y" "bc"

mapContextBy :: (String -> Bool) -> (String -> String) -> Context a -> Context a Source #

Transform the respective string results of all fields in a context satisfying a predicate. For example,

mapContextBy (=="y") (++"c") (constField "x" "a" <> constField "y" "b")

is equivalent to

constField "x" "a" <> constField "y" "bc"

defaultContext :: Context String Source #

A context that contains (in that order)

  1. A $body$ bodyField
  2. Metadata fields
  3. A $url$ urlField
  4. A $path$ pathField
  5. A $title$ titleField

This order means that all of the fields, except $body$, can have their values replaced by metadata fields of the same name. For example, a context from a file at posts/foo.markdown has a default title foo. However, with a metadata field:

---
title: The Foo Story
---

The $title$ will be replaced with The Foo Story.

bodyField :: String -> Context String Source #

Body of the item, that is, the main content of the underlying file

metadataField :: Context a Source #

Map any field to its metadata value, if present

urlField :: String -> Context a Source #

Absolute url to the resulting item. For an example item that produces a file posts/foo.html, this field contains "posts/foo.html"

pathField :: String -> Context a Source #

Filepath of the underlying file of the item. For an example underlying file posts/foo.markdown, this field contains "posts/foo.markdown"

titleField :: String -> Context a Source #

Basename of the underlying file of the item. For an example underlying file posts/foo.markdown, this field contains "foo"

snippetField :: Context String Source #

A context that allows snippet inclusion. In processed file, use as:

...
$snippet("path/to/snippet/")$
...

The contents of the included file will not be interpolated like partial does it.

dateField Source #

Arguments

:: String

Key in which the rendered date should be placed

-> String

Format to use on the date

-> Context a

Resulting context

When the metadata has a field called published in one of the following formats then this function can render the date.

  • Mon, 06 Sep 2010 00:01:00 +0000
  • Mon, 06 Sep 2010 00:01:00 UTC
  • Mon, 06 Sep 2010 00:01:00
  • 2010-09-06T00:01:00+0000
  • 2010-09-06T00:01:00Z
  • 2010-09-06T00:01:00
  • 2010-09-06 00:01:00+0000
  • 2010-09-06 00:01:00
  • September 06, 2010 00:01 AM

Following date-only formats are supported too (00:00:00 for time is assumed)

  • 2010-09-06
  • 06.09.2010
  • September 06, 2010

Alternatively, when the metadata has a field called path in a folder/yyyy-mm-dd-title.extension format (the convention for pages) and no published metadata field set, this function can render the date. This pattern matches the file name or directory names that begins with yyyy-mm-dd . For example: folder/yyyy-mm-dd-titledist/main.extension . In case of multiple matches, the rightmost one is used.

As another alternative, if none of the above matches, and the file has a path which contains nested directories specifying a date, then that date will be used. In other words, if the path is of the form **/yyyymmdd/main.extension . As above, in case of multiple matches, the rightmost one is used.

dateFieldWith Source #

Arguments

:: TimeLocale

Output time locale

-> String

Destination key

-> String

Format to use on the date

-> Context a

Resulting context

This is an extended version of dateField that allows you to specify a time locale that is used for outputting the date. For more details, see dateField and formatTime.

getItemUTC Source #

Arguments

:: (MonadMetadata m, MonadFail m) 
=> TimeLocale

Output time locale

-> Identifier

Input page

-> m UTCTime

Parsed UTCTime

Parser to try to extract and parse the time from the published field or from the filename. See dateField for more information. Exported for user convenience.

getItemModificationTime :: Identifier -> Compiler UTCTime Source #

Get the time on which the actual file was last modified. This only works if there actually is an underlying file, of couse.

modificationTimeField Source #

Arguments

:: String

Key

-> String

Format

-> Context a

Resulting context

Creates a field with the last modification date of the underlying item.

modificationTimeFieldWith Source #

Arguments

:: TimeLocale

Time output locale

-> String

Key

-> String

Format

-> Context a

Resulting context

Creates a field with the last modification date of the underlying item in a custom localisation format (see formatTime).

teaserField Source #

Arguments

:: String

Key to use

-> Snapshot

Snapshot to load

-> Context String

Resulting context

A context with "teaser" key which contain a teaser of the item. The item is loaded from the given snapshot (which should be saved in the user code before any templates are applied).

teaserFieldWithSeparator Source #

Arguments

:: String

Separator to use

-> String

Key to use

-> Snapshot

Snapshot to load

-> Context String

Resulting context

A context with "teaser" key which contain a teaser of the item, defined as the snapshot content before the teaser separator. The item is loaded from the given snapshot (which should be saved in the user code before any templates are applied).

missingField :: Context a Source #

Constantly reports any field as missing. Mostly for internal usage, it is the last choice in every context used in a template application.