Support for Content-Disposition: inline

Actually all these changes do is supporting an incoming `?preview=1` query
argument on download URLs and forward the `x-disposition = inline` extra to
Giftless when requesting the download URL.

At that point datopian/giftless#90 will kick in
and the storage backend will return the appropiate headers.

The only way to pass this parameter all the way down to the action that
requests the downloadURL was to add a new argument to the download
handlers. This would break backwards compatibility so I've added code to
support plugin hooks that don't support the new `inline` arg.

ckanext/blob_storage/actions.py

@@ -22,15 +22,17 @@ def get_resource_download_spec(context, data_dict):
         if k not in resource:
             return {}
 
-    return get_lfs_download_spec(context, resource)
+    inline = toolkit.asbool(data_dict.get('inline'))
+    return get_lfs_download_spec(context, resource, inline=inline)
 
 
 def get_lfs_download_spec(context,  # type: Dict[str, Any]
                           resource,  # type: Dict[str, Any]
                           sha256=None,  # type: Optional[str]
                           size=None,  # type: Optional[int]
                           filename=None,  # type: Optional[str]
-                          storage_prefix=None  # type: Optional[str]
+                          storage_prefix=None,  # type: Optional[str]
+                          inline=False,  # type: Optional[bool]
                           ):  # type: (...) -> Dict[str, Any]
     """Get the LFS download spec (URL and headers) for a resource
 
@@ -55,6 +57,10 @@ def get_lfs_download_spec(context,  # type: Dict[str, Any]
     client = context.get('download_lfs_client', LfsClient(helpers.server_url(), authz_token))
 
     resources = [{"oid": sha256, "size": size, "x-filename": filename}]
+
+    if inline:
+        resources[0]["x-disposition"] = "inline"
+
     object_spec = _get_resource_download_lfs_objects(client, storage_prefix, resources)[0]
 
     assert object_spec['oid'] == sha256

ckanext/blob_storage/blueprints.py

@@ -1,7 +1,7 @@
 """ckanext-blob-storage Flask blueprints
 """
 from ckan.plugins import toolkit
-from flask import Blueprint
+from flask import Blueprint, request
 
 from .download_handler import call_download_handlers, call_pre_download_handlers, get_context
 
@@ -24,10 +24,13 @@ def download(id, resource_id, filename=None):
         if id != resource['package_id']:
             return toolkit.abort(404, toolkit._('Resource not found belonging to package'))
 
+        inline = toolkit.asbool(request.args.get('preview'))
+
         package = toolkit.get_action('package_show')(context, {'id': id})
 
         resource = call_pre_download_handlers(resource, package)
-        return call_download_handlers(resource, package, filename)
+
+        return call_download_handlers(resource, package, filename, inline)
 
     except toolkit.ObjectNotFound:
         return toolkit.abort(404, toolkit._('Resource not found'))

ckanext/blob_storage/download_handler.py

@@ -1,4 +1,5 @@
 import os
+import inspect
 
 from ckan import model, plugins
 from ckan.lib import uploader
@@ -31,28 +32,34 @@ def call_pre_download_handlers(resource, package):
     return resource
 
 
-def call_download_handlers(resource, package, filename=None):
+def call_download_handlers(resource, package, filename=None, inline=False):
     """Call all registered plugins download handlers
     """
     for plugin in plugins.PluginImplementations(IResourceDownloadHandler):
         if not hasattr(plugin, 'resource_download'):
             continue
-        response = plugin.resource_download(resource, package, filename)
+
+        if _handler_supports_inline_arg(plugin.resource_download):
+            response = plugin.resource_download(resource, package, filename, inline)
+        else:
+            response = plugin.resource_download(resource, package, filename)
+
         if response:
             return response
 
     return fallback_download_method(resource)
 
 
-def download_handler(resource, _, filename=None):
+def download_handler(resource, _, filename=None, inline=False):
     """Get the download URL from LFS server and redirect the user there
     """
     if resource.get('url_type') != 'upload' or not resource.get('lfs_prefix'):
         return None
-
     context = get_context()
     data_dict = {'resource': resource,
-                 'filename': filename}
+                 'filename': filename,
+                 'inline': inline}
+
     resource_download_spec = tk.get_action('get_resource_download_spec')(context, data_dict)
     href = resource_download_spec.get('href')
 
@@ -76,3 +83,14 @@ def fallback_download_method(resource):
         return tk.abort(404, tk._('No download is available'))
 
     return tk.redirect_to(resource[u'url'])
+
+
+def _handler_supports_inline_arg(handler_function):
+    try:
+        # Python 3
+        args = inspect.getfullargspec(handler_function).args
+    except AttributeError:
+        # Python 2
+        args = inspect.getargspec(handler_function).args
+
+    return 'inline' in args

ckanext/blob_storage/interfaces.py

@@ -27,14 +27,16 @@ def pre_resource_download(self, resource, package):
         """
         pass
 
-    def resource_download(self, resource, package, filename=None):
-        # type: (Dict[str, Any], Dict[str, Any], Optional[str]) -> Any
+    def resource_download(self, resource, package, filename=None, inline=False):
+        # type: (Dict[str, Any], Dict[str, Any], Optional[str], Optional[bool]) -> Any
         """Download a resource
 
         Called to download a resource, with the resource, package and filename
         (if specified in the download request URL) already provided, and after
         some basic authorization checks such as ``resource_show`` have been
-        performed.
+        performed. Additionally if the resource needs to be displayed inline
+        (ie not served as an attachment) the `inline=True` argument can be
+        passed.
 
         All resource download handlers will be called in plugin load order by
         the Blueprint view function responsible for file downloads. The first

ckanext/blob_storage/plugin.py

@@ -141,5 +141,5 @@ def register_authz_bindings(self, authorizer):
 
     # IResourceDownloadHandler
 
-    def resource_download(self, resource, package, filename=None):
-        return download_handler(resource, package, filename)
+    def resource_download(self, resource, package, filename=None, inline=False):
+        return download_handler(resource, package, filename, inline)

ckanext/blob_storage/tests/test_blueprint.py

@@ -0,0 +1,67 @@
+import mock
+import pytest
+
+from ckan.plugins import toolkit
+from ckan.tests import factories
+
+
+@pytest.mark.usefixtures('clean_db')
+def test_preview_arg(app):
+
+    org = factories.Organization()
+    dataset = factories.Dataset(owner_org=org['id'])
+    resource = factories.Resource(
+        package_id=dataset['id'],
+        url_type='upload',
+        sha256='cc71500070cf26cd6e8eab7c9eec3a937be957d144f445ad24003157e2bd0919',
+        size=12,
+        lfs_prefix='lfs/prefix'
+    )
+
+    with mock.patch('ckanext.blob_storage.blueprints.call_download_handlers') as m:
+
+        m.return_value = ''
+
+        url = toolkit.url_for(
+            'blob_storage.download',
+            id=dataset['id'],
+            resource_id=resource['id'],
+            preview=1
+        )
+
+        app.get(url)
+
+        args = m.call_args
+
+        assert args[0][0]['id'] == resource['id']   # resource
+        assert args[0][1]['id'] == dataset['id']    # dataset
+        assert args[0][2] is None                   # filename
+        assert args[0][3] is True                   # inline
+
+        url = toolkit.url_for(
+            'blob_storage.download',
+            id=dataset['id'],
+            resource_id=resource['id'],
+            filename='test.csv',
+            preview=1
+        )
+
+        app.get(url)
+
+        args = m.call_args
+
+        assert args[0][2] == 'test.csv'             # filename
+        assert args[0][3] is True                   # inline
+
+        url = toolkit.url_for(
+            'blob_storage.download',
+            id=dataset['id'],
+            resource_id=resource['id'],
+            filename='test.csv',
+        )
+
+        app.get(url)
+
+        args = m.call_args
+
+        assert args[0][3] is False                   # inline