ckanext-scheming
This CKAN extension provides a way to configure and share metadata schemas using a
YAML or JSON schema description. Custom validation and template snippets for editing
and display are supported.
Table of contents:
- Requirements
- Installation
- Configuration
- Action API Endpoints
- Running the Tests
Requirements
This plugin is compatible with CKAN 2.10 or later.
Installation
You can install the extension with the following shell commands:
cd $CKAN_VENV/src/
pip install -e "git+https://github.com/ckan/ckanext-scheming.git#egg=ckanext-scheming"
Configuration
Set the schemas you want to use with configuration options:
# Each of the plugins is optional depending on your use
ckan.plugins = scheming_datasets scheming_groups scheming_organizations
# module-path:file to schemas being used
scheming.dataset_schemas = ckanext.spatialx:spatialx_schema.yaml
ckanext.spatialx:spatialxy_schema.yaml
# will try to load "spatialx_schema.yaml" and "spatialxy_schema.yaml"
# as dataset schemas
# For group and organization schemas (replace myplugin with your custom plugin)
scheming.group_schemas = ckanext.scheming:group_with_bookface.json
ckanext.myplugin:/etc/ckan/default/group_with_custom_fields.json
scheming.organization_schemas = ckanext.scheming:org_with_dept_id.json
ckanext.myplugin:org_with_custom_fields.json
#
# URLs may also be used, e.g:
#
# scheming.dataset_schemas = http://example.com/spatialx_schema.yaml
# Preset files may be included as well. The default preset setting is:
scheming.presets = ckanext.scheming:presets.json
# The is_fallback setting may be changed as well. Defaults to false:
scheming.dataset_fallback = false
Schemas for datasets, groups, and organizations can be defined using either JSON or YAML files. The extension automatically detects the format based on the file extension (.json, .yaml, or .yml). While examples often show YAML for datasets and JSON for organizations, you are free to use whichever format you prefer for any entity type.
Schema Types
With this plugin, you can customize the group, organization, and dataset entities in CKAN. Adding and enabling a schema will modify the forms used to update and create each entity, indicated by the respective type property at the root level. Such as group_type, organization_type, and dataset_type. Non-default types are supported properly as is indicated throughout the examples.
Example Schemas
Dataset schemas:
These schemas are included in ckanext-scheming and may be enabled
with e.g: scheming.dataset_schemas = ckanext.scheming:camel_photos.yaml
These schemas use presets defined in
presets.json.
Group schemas:
Organization schemas:
Common Schema Keys
about_url
about_url: https://github.com/link-to-my-project
about_url is a link to human-readable information about this schema.
ckanext-scheming automatically publishes your
schema and this link allows users to learn more about it.
Dataset Schema Keys
dataset_type
dataset_type: camel-photos
This is the “type” field stored in the dataset.
It is also used to set the URL for searching this type of dataset.
Normal datasets would be available under the URL /dataset, but datasets with
the camel_photos.json schema above would appear under /camel-photos instead.
dataset_fields, resource_fields
dataset_fields:
- field_name: title
label: Title
preset: title
- field_name: name
label: URL
preset: dataset_slug
...
Fields are specified in the order you
would like them to appear in the dataset and resource editing
pages.
Fields you exclude will not be shown to the end user, and will not
be accepted when editing or updating this type of dataset.
before_validators, after_validators
before_validators: validator_name
after_validators: validator_name
Runs validator functions before and after the dataset_type package or organization_type/group_type group is created/updated.
See validators for a description of the values accepted.
draft_fields_required
Enforce required fields even if a dataset is still in draft state.
Default: true
draft_fields_required: false
Set to false to allow saving dataset and resource metadata even
if some required fields have not been provided as long as the dataset
is still in draft state (has not been published).
Group / Organization Schema Keys
group_type
group_type: group
is used for modifying the default group schema
group_type: theme
is an example of defining a custom group type, as seen in the example schemas above
Like dataset_type, a group_type of group allows you to customize the default group schema under the URL /group, such as the modified schema in group_with_bookface.json, but a schema with a custom type such as custom_group_with_status.json schema above would appear under /theme instead, because its group_type field is set to “theme”.
organization_type
organization_type: organization
is used for modifying the default organization schema
organization_type: publisher
is an example of defining a custom organization type, as seen in the example schemas above
fields
fields:
- field_name: title
label: Name
form_snippet: large_text.html
form_attrs:
data_module: slug-preview-target
form_placeholder: My Organization
...
A single fields list replaces the dataset_fields and resource_fields schema properties in dataset schemas.
Field Keys
field_name
The field_name value is the name of an existing CKAN dataset or resource field (columns in the package or resource database tables) or a new extra field.
Existing dataset field names include (but are not limited to):
name - the URI for the datasettitlenotes - the dataset descriptionauthorauthor_emailmaintainermaintainer_email
New field names should follow the current lowercase_with_underscores naming convention. Don’t name your field mySpecialField, use my_special_field instead.
The ckan_dataset.yaml file provided in this extension is just an example schema that mirrors standard CKAN behavior. It defines many of these standard fields, but you are free to include or exclude them in your custom schemas.
label
The label value is a human-readable label for this field as
it will appear in the dataset editing form.
This label may be a string or an object providing multiple
language versions:
- field_name: title
label:
en: Title
fr: Titre
When using a plain string translations will be provided with gettext:
- field_name: title
label: Title
repeating_subfields
This field is the parent of group of repeating subfields. The value is
a list of fields entered the same way as normal fields.
[!NOTE]
CKAN needs an IPackageController plugin with before_index to
convert repeating subfields to formats that can be indexed by solr. For
testing you may use the included scheming_nerf_index plugin to encode
all repeating fields as JSON strings to prevent solr errors.
repeating_label may be used to provide a singular version of the label
for each group.
Optional form presentation keys:
repeating_collapse: true - wrap the repeating field group in a
Bootstrap accordion (collapsed by default)repeating_grid: true - render each repeating panel in a Bootstrap
grid row (default column class col-md-6)col_class - Bootstrap column class used when repeating_grid is
enabled (e.g. col-md-4)
- field_name: contacts
label: Contacts
repeating_label: Contact
repeating_collapse: true
repeating_grid: true
col_class: col-md-4
repeating_subfields:
- field_name: address
label: Address
required: true
- field_name: city
label: City
- field_name: phone
label: Phone Number
label: This is the human-readable label for the entire group of repeating fields (e.g., “Contacts”). It typically appears as the header for the section.repeating_label: This is the label used for the singular item, often used in the “Add [Label]” button (e.g., “Add Contact”).
Both label and repeating_label support internationalization dictionaries:
- field_name: contacts
label:
en: Contacts
es: Contactos
repeating_label:
en: Contact
es: Contacto
repeating_subfields:
- field_name: address
label:
en: Address of the contact point
es: Dirección del punto de contacto
required: true
...
start_form_page
Dataset fields may be divided into separate form pages for creation
and editing.
Adding start_form_page to a field marks this field as the start of a
new page of fields.
- start_form_page:
title: Detailed Metadata
description:
These fields improve search and give users important links
field_name: address
label: Address
A title and description should be provided to help with navigation.
These values may be strings or objects providing multiple
language versions of text.
required
required: true
Use for fields that must be included. Set to false or
don’t include this key for fields that are optional.
Setting to true will mark the field as required in the editing form
and affects the behavior of the scheming_required field validator.
choices
The choices list may be provided for
select and multiple choice fields.
List elements include labels for human-readable text for
each element (may be multiple languages like a field label)
and values that will be stored in the dataset or resource:
- field_name: category
preset: select
choices:
- value: bactrian
label: Bactrian Camel
- value: hybrid
label: Hybrid Camel
For storing non-string values see output_validators.
For required select fields you may also want to add this setting
so that users are forced to choose an item in the form, otherwise the first
choice will be selected in the form by default:
form_include_blank_choice: true
To set the number of choices displayed in the multiple_select
form snippets use:
select_size: 5
To sort choices alphabetically in form
and display snippets use:
sorted_choices: true
choices_helper
If a choices list is not provided you must provide a choices_helper
function that will return a list of choices in the same format as
the choices list above.
You may register your own helper function or use the
scheming_datastore_choices helper included in ckanext-scheming:
- field_name: country
preset: select
choices_helper: scheming_datastore_choices
datastore_choices_resource: countries-resource-id-or-alias
datastore_choices_columns:
value: Country Code
label: English Country Name
datastore_additional_choices:
- value: none
label: None
- value: na
label: N/A
default
Pre-fill new forms with this default value for this field.
default_jinja2
Pre-fill new forms with a jinja2 snippet defined by default_jinja2, useful
if you need to call a template helper function or use jinja2 logic to determine
the default value for this field.
preset
A preset specifies a set of default values for other field keys. They
allow reuse of definitions for validation and snippets for common field types.
Presets can be used for all schemas: datasets, groups, and organizations.
This extension includes the following presets in presets.json:
preset: title
title validation and large text form snippet
preset: select
validation that choice is from choices, form select box and display snippet
preset: radio
validation that choice is from choices, form radio buttons group and display snippet
preset: multiple_checkbox
multiple choice from choices rendered as checkboxes in the form, stored as a list of values
preset: multiple_select
multiple choice from choices rendered as a multiple select box in the form, stored as a list of values
preset: multiple_text
repeating text field with add and remove buttons, stored as a list of strings
preset: date
date validation and form snippet
preset: datetime
date and time validation and form snippet
preset: dataset_slug
dataset slug validation and form snippet that autofills the value from the title field
preset: tag_string_autocomplete
tag string validation and form autocomplete
preset: dataset_organization
organization validation and form select box
preset: resource_url_upload
resource url validaton and link/upload form field
preset: resource_format_autocomplete
resource format validation and form autocomplete
preset: organization_url_upload
organization url validaton and link/upload form field
format guessing based on url and autocompleting form field
preset: json_object
JSON based input. Only JSON objects are supported. The input JSON will be loaded during output (eg when loading the dataset in a template or via the API
preset: markdown
markdown text area and display
You may define your own presets by adding additional files to the scheming.presets
configuration setting.
The form_snippet value is the name of the snippet template to
use for this field in the dataset or resource editing form.
A number of snippets are provided with this
extension, but you may also provide your own by creating templates
under scheming/form_snippets/ in a template directory in your
own extension.
This snippet is passed the field dict containing all the keys and
values in this field record, including any additional ones
you added to your that aren’t handled by this extension.
The included form snippets may be found under templates/scheming/form_snippets.
display_snippet
The display_snippet value is the name of the snippet template to
use for this field in the dataset, resource, group or organization view page.
A number of snippets are provided with this
extension, but you may also provide your own by creating templates
under scheming/display_snippets/ in a template directory in your
own extension.
This snippet is passed the field dict containing all the keys and
values in this field record, including any additional ones
you added to your that aren’t handled by this extension.
The included display snippets may be found under templates/scheming/display_snippets.
If display_snippet: null is used the field will be removed from the view page.
display_property
- field_name: author
label: Author
display_property: dc:creator
Set a property attribute on dataset fields displayed as “Additional Info”, useful for adding RDF markup.
validators
The validators value is a space-separated string of validator and converter
functions to use for this field when creating or updating data. For core fields
the validators default to the ones defined in the CKAN core schemas.
[!WARNING]
Use scheming_required as the first validator
or the required field setting will be ignored.
scheming_required applies either the not_empty or ignore_missing
validator based on the required field setting.
When a validator name is followed by parenthesis the function is called
passing the comma-separated values within and the result is used as the
validator/converter.
validators: scheming_required if_empty_same_as(name) unicode_safe
is the same as a form plugin using the validators:
[
get_validator('scheming_required'),
get_validator('if_empty_same_as')("name"),
get_validator('unicode_safe')
]
If validator parameters can be parsed as a valid python literals,
they are passed with the original type. If not, all parameters passed
as strings. In addition, space character is not allowed in argument
position. Use its HEX code instead \\x20.
validators: xxx(hello,world) # xxx("hello", "world")
validators: xxx(hello,1) # xxx("hello", "1")
validators: xxx("hello",1,None) # xxx("hello", 1, None)
validators: xxx("hello\\x20world") # xxx("hello world")
[!NOTE]
ckanext-scheming automatically adds a call to convert_to_extras
for extra fields when required.
New validators and converters may be registered using the
IValidators plugin interface.
Validators that need access to other values in this schema (e.g.
to test values against the choices list) may be decorated with
the scheming.validation.scheming_validator
function. This decorator will make scheming pass this field dict to the
validator and use its return value for validation of the field.
CKAN’s validator functions reference
lists available validators ready to be used.
output_validators
Internally all extra fields are stored as strings. If you are attempting to save and restore other types of data you will need to use output validators.
For example if you use a simple “yes/no” question, you will need to let ckanext-scheming know that this data needs to be stored and retrieved as a boolean. This is acheieved using validators and output_validators keys.
- field_name: is_camel_friendly
label: Is this camel friendly?
required: true
preset: select
choices:
- value: false
label: "No"
- value: true
label: "Yes"
validators: scheming_required boolean_validator
output_validators: boolean_validator
The output_validators value is like validators but used when
retrieving values from the database instead of when saving them.
These validators may be used to transform the data before it is
sent to the user.
[!NOTE]
ckanext-scheming automatically adds calls to convert_from_extras
for extra fields when required.
create_validators
The create_validators value, if present, overrides validators during creation only.
When updating an existing record, the standard validators list is used instead.
This is useful for:
- Fields that are mandatory when creating a dataset but read-only or optional during updates.
- Setting initial default values or identifiers that shouldn’t be validated the same way afterwards.
- field_name: source_id
label: Source dataset identifier
form_placeholder: 'INT-12345'
# Creation: must be present and valid
create_validators: scheming_required not_empty unicode_safe
# Update: optional, but if provided it must still be valid
validators: ignore_missing unicode_safe
In this example, source_id is required when the dataset is created.
On updates the field is optional: if it is omitted the update passes; if it is
provided it still must be a valid string according to the unicode_safe
validator. This is useful when introducing a new required field without
breaking updates to existing legacy datasets that do not yet have this value.
help_text
help_text: License definitions and additional information
If this key is supplied, its value will be shown after the field as help text.
Help text may be provided in multiple languages like label fields.
Help text must be plain text, no markdown or HTML are allowed unless:
help_allow_html: true
Allow HTML inside the help text if set to true. Default is false.
Adjust the position of help_text with:
help_inline: true
Display help text inline (next to the field) if set to true. Default is false (display help text under the field).
Action API Endpoints
The extension adds action endpoints which expose any configured schemas via:
https://github.com/ckan/ckanext-scheming/blob/master/ckanext/scheming/logic.py
Some examples:
Calling http://localhost:5000/api/3/action/scheming_dataset_schema_list
Returns:
{
help: "http://localhost:5005/api/3/action/help_show?name=scheming_dataset_schema_list",
success: true,
result: [
"dataset",
"camel-photos"
]
}
Calling http://localhost:5000/api/3/action/scheming_dataset_schema_show?type=dataset
Returns:
{
help: "http://localhost:5005/api/3/action/help_show?name=scheming_dataset_schema_show",
success: true,
result: {
dataset_type: "dataset",
about: "A reimplementation of the default CKAN dataset schema",
about_url: "https://github.com/ckan/ckanext-scheming",
dataset_fields: [...],
resource_fields: [...]
}
}
The full list of API actions are available in ckanext/scheming/logic.py
Running the Tests
To run the tests:
pytest --ckan-ini=test.ini ckanext/scheming/tests
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