feat: add grpc transcoding + tests

google/api_core/path_template.py

@@ -66,7 +66,7 @@ def _expand_variable_match(positional_vars, named_vars, match):
     """Expand a matched variable with its value.
 
     Args:
-        positional_vars (list): A list of positonal variables. This list will
+        positional_vars (list): A list of positional variables. This list will
             be modified.
         named_vars (dict): A dictionary of named variables.
         match (re.Match): A regular expression match.
@@ -195,3 +195,58 @@ def validate(tmpl, path):
     """
     pattern = _generate_pattern_for_template(tmpl) + "$"
     return True if re.match(pattern, path) is not None else False
+
+def transcode(http_options, **request_kwargs):
+    """Transcodes a grpc request pattern into a proper HTTP request following the rules outlined here,
+       https://github.com/googleapis/googleapis/blob/master/google/api/http.proto#L44-L312
+
+        Args:
+            http_options (list(dict)): A list of dicts which consist of these keys,
+                'method'    (str): The http method
+                'uri'       (str): The path template
+                'body'      (str): The body field name (optional)
+                (This is a simplified representation of the proto option `google.api.http`)
+            request_kwargs (dict) : A dict representing the request object
+
+        Returns:
+            dict: The transcoded request with these keys,
+                'method'        (str)   : The http method
+                'uri'           (str)   : The expanded uri
+                'body'          (dict)  : A dict representing the body (optional)
+                'query_params'  (dict)  : A dict mapping query parameter variables and values
+
+        Raises:
+            ValueError: If the request does not match the given template.
+    """
+    answer = {}
+    for http_option in http_options:
+
+        # Assign path
+        uri_template = http_option['uri']
+        path_fields = [match.group('name') for match in _VARIABLE_RE.finditer(uri_template)]
+        path_args = {field:request_kwargs.get(field, None) for field in path_fields}
+        leftovers = {k:v for k,v in request_kwargs.items() if k not in path_args}
+        answer['uri'] = expand(uri_template, **path_args)
+
+        if not validate(uri_template, answer['uri']) or not all(path_args.values()):
+            continue
+
+        # Assign body and query params
+        body = http_option.get('body')
+
+        if body:
+            if body == '*':
+                answer['body'] = leftovers
+                answer['query_params'] = {}
+            else:
+                try:
+                    answer['body'] = leftovers.pop(body)
+                except KeyError:
+                    continue
+                answer['query_params'] = leftovers
+        else:
+            answer['query_params'] = leftovers
+        answer['method'] = http_option['method']
+        return answer
+
+    raise ValueError("Request obj does not match any template")

tests/unit/test_path_template.py

@@ -113,3 +113,110 @@ def test__replace_variable_with_pattern():
     match.group.return_value = None
     with pytest.raises(ValueError, match="Unknown"):
         path_template._replace_variable_with_pattern(match)
+
+
+@pytest.mark.parametrize(
+    'http_options, request_kwargs, expected_result',
+    [
+        [[['get','/v1/no/template','']],
+        {'foo':'bar'},
+        ['get','/v1/no/template',{},{'foo':'bar'}]],
+
+        # Single templates
+        [[['get','/v1/{field}','']],
+        {'field':'parent'},
+        ['get','/v1/parent',{},{}]],
+
+        [[['get','/v1/{field.sub}','']],
+        {'field.sub':'parent', 'foo':'bar'},
+        ['get','/v1/parent',{},{'foo':'bar'}]],
+
+        # Single segment wildcard
+        [[['get','/v1/{field=*}','']],
+        {'field':'parent'},
+        ['get','/v1/parent',{},{}]],
+
+        [[['get','/v1/{field=a/*/b/*}','']],
+        {'field':'a/parent/b/child','foo':'bar'},
+        ['get','/v1/a/parent/b/child',{},{'foo':'bar'}]],
+
+        # Double segment wildcard
+        [[['get','/v1/{field=**}','']],
+        {'field':'parent/p1'},
+        ['get','/v1/parent/p1',{},{}]],
+
+        [[['get','/v1/{field=a/**/b/**}','']],
+        {'field':'a/parent/p1/b/child/c1', 'foo':'bar'},
+        ['get','/v1/a/parent/p1/b/child/c1',{},{'foo':'bar'}]],
+
+        # Combined single and double segment wildcard
+        [[['get','/v1/{field=a/*/b/**}','']],
+        {'field':'a/parent/b/child/c1'},
+        ['get','/v1/a/parent/b/child/c1',{},{}]],
+
+        [[['get','/v1/{field=a/**/b/*}/v2/{name}','']],
+        {'field':'a/parent/p1/b/child', 'name':'first', 'foo':'bar'},
+        ['get','/v1/a/parent/p1/b/child/v2/first',{},{'foo':'bar'}]],
+
+        # Single field body
+        [[['post','/v1/no/template','data']],
+        {'data':{'id':1, 'info':'some info'},'foo':'bar'},
+        ['post','/v1/no/template',{'id':1, 'info':'some info'},{'foo':'bar'}]],
+
+        [[['post','/v1/{field=a/*}/b/{name=**}','data']],
+        {'field':'a/parent','name':'first/last','data':{'id':1, 'info':'some info'},'foo':'bar'},
+        ['post','/v1/a/parent/b/first/last',{'id':1, 'info':'some info'},{'foo':'bar'}]],
+
+        # Wildcard body
+        [[['post','/v1/{field=a/*}/b/{name=**}','*']],
+        {'field':'a/parent','name':'first/last','data':{'id':1, 'info':'some info'},'foo':'bar'},
+        ['post','/v1/a/parent/b/first/last',{'data':{'id':1, 'info':'some info'},'foo':'bar'},{}]],
+
+        # Additional bindings
+        [[['post','/v1/{field=a/*}/b/{name=**}','extra_data'], ['post','/v1/{field=a/*}/b/{name=**}','*']],
+        {'field':'a/parent','name':'first/last','data':{'id':1, 'info':'some info'},'foo':'bar'},
+        ['post','/v1/a/parent/b/first/last',{'data':{'id':1, 'info':'some info'},'foo':'bar'},{}]],
+
+        [[['get','/v1/{field=a/*}/b/{name=**}',''],['get','/v1/{field=a/*}/b/first/last','']],
+        {'field':'a/parent','foo':'bar'},
+        ['get','/v1/a/parent/b/first/last',{},{'foo':'bar'}]],
+    ]
+)
+def test_transcode(http_options, request_kwargs, expected_result):
+    http_options, expected_result = helper_test_transcode(http_options, expected_result)
+    result = path_template.transcode(http_options, **request_kwargs)
+    assert result == expected_result
+
+
+@pytest.mark.parametrize(
+    'http_options, request_kwargs',
+    [
+        [[['get','/v1/{name}','']], {'foo':'bar'}],
+        [[['get','/v1/{name}','']], {'name':'first/last'}],
+        [[['get','/v1/{name=mr/*/*}','']], {'name':'first/last'}],
+        [[['post','/v1/{name}','data']], {'name':'first/last'}],
+    ]
+)
+def test_transcode_fails(http_options, request_kwargs):
+    http_options, _ = helper_test_transcode(http_options, range(4))
+    with pytest.raises(ValueError):
+        path_template.transcode(http_options, **request_kwargs)
+
+
+def helper_test_transcode(http_options_list, expected_result_list):
+    http_options = []
+    for opt_list in http_options_list:
+        http_option = {'method':opt_list[0], 'uri':opt_list[1]}
+        if opt_list[2]:
+            http_option['body'] = opt_list[2]
+        http_options.append(http_option)
+
+    expected_result = {
+        'method':expected_result_list[0],
+        'uri':expected_result_list[1],
+        'query_params':expected_result_list[3]
+    }
+    if (expected_result_list[2]):
+        expected_result['body'] = expected_result_list[2]
+
+    return(http_options, expected_result)