recipe_modules/jsonutil/api.py

# Copyright 2019 The Fuchsia Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

import re

from recipe_engine import recipe_api


class JsonUtilApi(recipe_api.RecipeApi):
    """JsonUtilApi contains JSON-related utilities."""

    def permissive_loads(self, text):
        """Extracts JSON from supplied text.

        The parsing is somewhat more permissive than the actual JSON spec; for
        example, commas are allowed after the last elements of arrays and
        objects.

        Args:
          text (str): Text containing a JSON string.

        Returns:
          A JSON object representing the extracted JSON string from the text.
        """
        # Strip any comma after the last element of an object or array.
        text = re.sub(r",(?=\s*[}\]])", "", text)
        try:
            return self.m.json.loads(text)
        except ValueError as e:
            raise self.m.step.StepFailure("failed to load JSON: %s" % str(e))

    def retrieve_nested_field(self, json_data, field):
        """Retrieve a field from a nested dict.

        Returns the first found value if it exists. Otherwise return None.

        For example, given the following data:

            data = {
                "list": [
                    {"foo": "bar"}
                ]
            }

        `retrieve_nested_field(data, "foo")` will return "bar".

        Args:
            json_data (Any): The JSON value (list, dict, etc.) to read from.
            field (str): The name of the field.
        """
        if isinstance(json_data, dict):
            if field in json_data:
                return json_data[field]
            for val in json_data.values():
                return_val = self.retrieve_nested_field(val, field)
                if return_val is not None:
                    return return_val
        if isinstance(json_data, list):
            for item in json_data:
                return_val = self.retrieve_nested_field(item, field)
                if return_val is not None:
                    return return_val
        return None