Retrieve JSON data from an external source

Allow the user to define a custom URL to retrieve the JSON
data (instead of hitting Read the Docs API) needed to add the banner
into the page.

This is useful when there is a git tag that doesn't want to be
updated, but now the warning message is out of date. So, by defining a
custom URL (potentially a JSON under the git repository served by
github, for example) this file is retrieved by the documentation and
displayed the custom message needed at certain date.

The JSON file can be updated independently from the documentation/tag/etc.

versionwarning/_static/js/versionwarning.src.js

@@ -80,6 +80,16 @@ function checkVersion(config) {
     });
 }
 
+function handleBanner(config) {
+    console.debug("handleBanner");
+    if (config.banner.custom) {
+        injectCustomWarningBanner(config);
+    }
+    else {
+        checkVersion(config);
+    }
+}
+
 function init() {
     console.debug("init");
     $.ajax({
@@ -90,11 +100,30 @@ function init() {
             if (banner) {
                 console.debug("There is already a banner added. No checking versions.")
             }
-            else if (config.banner.custom) {
-                injectCustomWarningBanner(config);
+            else if (config.meta.json_url && !config.meta.retrieve_data_from_api) {
+                console.debug("Retrieving dynamic data from 'json_url'.")
+                $.ajax({
+                    dataType: "json",
+                    cache: "false",
+                    url: config.meta.json_url,
+                    success: function(dynamic_config) {
+                        if (config.version.slug in dynamic_config) {
+                            handleBanner(dynamic_config[config.version.slug]);
+                        }
+                        else if (config.meta.only_override_banner) {
+                            handleBanner(config);
+                        }
+                        else {
+                            log.error("JSON data from " + config.meta.json_url + " does not have a warning banner for " + config.version.slug);
+                        }
+                    },
+                    error: function() {
+                        console.error("Error loading dynamic config object");
+                    },
+                });
             }
             else {
-                checkVersion(config);
+                handleBanner(config);
             }
         },
         error: function() {

versionwarning/exceptions.py

@@ -0,0 +1,16 @@
+# -*- coding: utf-8 -*-
+
+
+class ConfigError(Exception):
+    """
+    Incompatible config exception.
+
+    This exception is risen when the extension detects configs that are
+    incompatible or that depends each other.
+    """
+
+    NO_JSON_URL = (
+        'No URL defined to retrieve JSON data. '
+        'The URL is mandatory when "versionwarning_retrieve_data_from_api" '
+        'is True'
+    )

versionwarning/extension.py

@@ -29,6 +29,11 @@ def setup(app):
     app.add_config_value('versionwarning_project_slug', os.environ.get('READTHEDOCS_PROJECT', None), 'html')
     app.add_config_value('versionwarning_project_version', os.environ.get('READTHEDOCS_VERSION', None), 'html')
 
+
+    app.add_config_value('versionwarning_retrieve_data_from_api', True, 'html')
+    app.add_config_value('versionwarning_json_url', None, 'html')
+    app.add_config_value('versionwarning_only_override_banner', True, 'html')
+
     if sphinx.version_info >= (1, 8):
         # ``config-initied`` requires Sphinx >= 1.8
         app.connect('config-inited', generate_versionwarning_data_json)

versionwarning/signals.py

@@ -3,6 +3,8 @@
 import json
 import os
 
+from versionwarning.exceptions import ConfigError
+
 
 STATIC_PATH = os.path.join(os.path.dirname(__file__), '_static')
 JSON_DATA_FILENAME = 'versionwarning-data.json'
@@ -27,6 +29,9 @@ def generate_versionwarning_data_json(app, config=None, **kwargs):
     if config is None:
         config = app.config
 
+    if not config.versionwarning_retrieve_data_from_api and not config.versionwarning_json_url:
+        raise ConfigError(ConfigError.NO_JSON_URL)
+
     if config.versionwarning_project_version in config.versionwarning_messages:
         custom = True
         message = config.versionwarning_messages.get(config.versionwarning_project_version)
@@ -43,30 +48,44 @@ def generate_versionwarning_data_json(app, config=None, **kwargs):
         admonition_type=config.versionwarning_admonition_type,
     )
 
-    data = json.dumps({
-        'meta': {
-            'api_url': config.versionwarning_api_url,
-        },
+    data = {
         'banner': {
-            'html': banner_html,
-            'id_div': config.versionwarning_banner_id_div,
-            'body_selector': config.versionwarning_body_selector,
-            'custom': custom,
+            config.versionwarning_project_version: {
+                'html': banner_html,
+                'id_div': config.versionwarning_banner_id_div,
+                'body_selector': config.versionwarning_body_selector,
+                'custom': custom,
+            },
         },
         'project': {
             'slug': config.versionwarning_project_slug,
         },
         'version': {
             'slug': config.versionwarning_project_version,
         },
-    }, indent=4)
+    }
+
+    if config.versionwarning_retrieve_data_from_api:
+        url_key = 'api_url'
+        url = config.versionwarning_api_url
+    else:
+        url_key = 'json_url'
+        url = config.versionwarning_json_url
+
+    data.update({
+        'meta': {
+            url_key: url,
+            'retrieve_data_from_api': config.versionwarning_retrieve_data_from_api,
+            'only_override_banner': config.versionwarning_only_override_banner,
+        },
+    })
 
     data_path = os.path.join(STATIC_PATH, 'data')
     if not os.path.exists(data_path):
         os.mkdir(data_path)
 
     with open(os.path.join(data_path, JSON_DATA_FILENAME), 'w') as f:
-        f.write(data)
+        f.write(json.dumps(data, indent=4))
 
     # Add the path where ``versionwarning-data.json`` file and
     # ``versionwarning.js`` are saved