Added documentation on field options

docs/development/module/fields.md

@@ -100,6 +100,121 @@ function mymodule_farm_entity_bundle_field_info(EntityTypeInterface $entity_type
 }
 ```
 
+## Field options
+
+The following keys are available to use when specifying fields:
+
+- `label`: What the field should be called when displayed to the user.
+- `description`: A description of the field and how to use it.
+- `computed`: Whether the field is computed.
+- `required`: Specify this to force the user to enter a value into this
+  field.
+- `revisionable`: Make the field revisionable, unless told otherwise.
+- `cardinality`: Set cardinality, if specified. If neither `cardinality`
+   or `multiple` is specified, this defaults to 1.
+- `multiple`: If `cardinality` is not specified and `multiple` is, set
+  the cardinality to unlimited.
+- `translatable`: Only makes the field translatable if it is specified.
+- `default_value_callback`: Sets the default value callback, if specified.
+- `type`: The datatype of the field, represented as a string. Click one of
+  the following or scroll down for additional options relating to each specific
+  type:
+  - [`boolean`](#boolean)
+  - [`entity_reference`](#entity-reference)
+  - [`entity_reference_revisions`](#entity-reference-revisions)
+  - [`file`](#file-and-image)
+  - [`image`](#file-and-image)
+  - [`fraction`](#fraction)
+  - [`geofield`](#geofield)
+  - [`id_tag`](#id-tag)
+  - [`inventory`](#inventory)
+  - [`list_string`](#list-string)
+  - [`string`](#string)
+  - [`string_long`](#long-string)
+  - [`timestamp`](#timestamp)
+
+- `hidden`: Hide the field in form and view displays, if specified. The
+  hidden option can either be set to `true`, which will hide it in both form and
+  view displays, or it can be set to `form` or `view`, which will only hide
+  it in the form or view display.
+- `form_display_options` & `view_display_options`: Override form and
+  view display options, if specified.
+- `weight`: Contains an associative array with the keys `form` and
+  `view`, giving hints on whereabouts the field should appear (See the
+  examples).
+
+### Type specific options
+
+#### Boolean
+
+Currently there are no boolean-specific options.
+
+#### Entity reference
+
+- `target_type`: Required. What sort of entity the reference should be
+  targeting. This can be one of:
+  - `asset`
+  - `log`
+  - `taxonomy_term`
+  - `user`
+  - `data_stream`
+- `target_bundle`: Used when `target_type` is set to `asset` or
+  `taxonomy_term`. Used to specify the bundle to look for.
+- `auto_create`: Used when `target_type` is set to `taxonomy_term`. If
+  `auto_create` is set, term references will be created automatically if not
+  already defined.
+
+#### Entity reference revisions
+
+- `target_type`: Required. This currently must be `quantity`.
+
+#### File and image
+
+- `file_directory`: The directory that the image will be uploaded to in
+  relation to the private file system path. If not set, this will be
+  `farm/[date:custom:Y]-[date:custom:m]`.
+- For images, the allowed file extensions are `png`, `gif`, `jpg` and `jpeg`.
+- For other files, the allowed file extensions are `csv`, `doc`, `docx`, `gz`,
+  `geojson`, `gpx`, `kml`, `kmz`, `logz`, `mp3`, `odp`, `ods`, `odt`, `ogg`,
+  `pdf`, `ppt`, `pptx`, `tar`, `tif`, `tiff`, `txt`, `wav`, `xls`, `xlsx` and
+  `zip`.
+
+#### Fraction
+
+Currently there are no fraction-specific options.
+
+#### Geofield
+
+Currently there are no geofield-specific options.
+
+#### ID tag
+
+Currently there are no ID tag-specific options.
+
+#### Inventory
+
+Currently there are no inventory-specific options.
+
+#### List string
+
+- `allowed_values`: Optionally specify allowed values.
+- `allowed_values_function`: Optionally specify a function that returns
+  the allowed values.
+
+#### String
+
+Maximum length of 255 characters. Currently there are no string-specific
+coptions.
+
+#### Long string
+
+This is for longer messages than the string type. Currently there are no long
+string-specific options.
+
+#### Timestamp
+
+Currently there are no long timestamp-specific options.
+
 ## Select options
 
 Certain fields on assets and logs include a list of options to select from.