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# -*- coding: utf-8 -*-
# This Source Code Form is subject to the terms of the Mozilla Public
# License, v. 2.0. If a copy of the MPL was not distributed with this
# file, You can obtain one at
Outputter to generate Rust code for metrics.
import enum
import json
import jinja2
from glean_parser import util
from glean_parser.metrics import CowString, Event, Rate
from util import generate_metric_ids, generate_ping_ids, get_metrics
from js import ID_BITS, ID_SIGNAL_BITS
# The list of all args to CommonMetricData.
# No particular order is required, but I have these in
# order just to be organized.
common_metric_data_args = [
def rust_datatypes_filter(value):
A Jinja2 filter that renders Rust literals.
Based on Python's JSONEncoder, but overrides:
- dicts and sets to raise an error
- sets to vec![] (used in labels)
- enums to become Class::Value
- lists to vec![] (used in send_in_pings)
- null to None
- strings to "value".into()
- Rate objects to a CommonMetricData initializer
(for external Denominators' Numerators lists)
class RustEncoder(json.JSONEncoder):
def iterencode(self, value):
if isinstance(value, dict):
raise ValueError("RustEncoder doesn't know dicts {}".format(str(value)))
elif isinstance(value, enum.Enum):
yield (value.__class__.__name__ + "::" + util.Camelize(
elif isinstance(value, set):
yield from self.iterencode(sorted(list(value)))
elif isinstance(value, list):
yield "vec!["
first = True
for subvalue in list(value):
if not first:
yield ", "
yield from self.iterencode(subvalue)
first = False
yield "]"
elif value is None:
yield "None"
# CowString is also a 'str' but is a special case.
# Ensure its case is handled before str's (below).
elif isinstance(value, CowString):
value = json.dumps(value)
yield f"::std::borrow::Cow::from({value})"
elif isinstance(value, str):
yield f"{json.dumps(value)}.into()"
elif isinstance(value, Rate):
yield "CommonMetricData {"
for arg_name in common_metric_data_args:
if hasattr(value, arg_name):
yield f"{arg_name}: "
yield from self.iterencode(getattr(value, arg_name))
yield ", "
yield " ..Default::default()}"
yield from super().iterencode(value)
return "".join(RustEncoder().iterencode(value))
def ctor(obj):
Returns the scope and name of the constructor to use for a metric object.
Necessary because LabeledMetric<T> is constructed using LabeledMetric::new
not LabeledMetric<T>::new
if getattr(obj, "labeled", False):
return "LabeledMetric::new"
return class_name(obj.type) + "::new"
def type_name(obj):
Returns the Rust type to use for a given metric or ping object.
if getattr(obj, "labeled", False):
label_enum = "super::DynamicLabel"
if obj.labels and len(obj.labels):
label_enum = f"{util.Camelize(}Label"
return f"LabeledMetric<Labeled{class_name(obj.type)}, {label_enum}>"
generate_enums = getattr(obj, "_generate_enums", []) # Extra Keys? Reasons?
if len(generate_enums):
for name, _ in generate_enums:
if not len(getattr(obj, name)) and isinstance(obj, Event):
return class_name(obj.type) + "<NoExtraKeys>"
# we always use the `extra` suffix,
# because we only expose the new event API
suffix = "Extra"
return "{}<{}>".format(
class_name(obj.type), util.Camelize( + suffix
generate_structure = getattr(obj, "_generate_structure", [])
if len(generate_structure):
generic = util.Camelize( + "Object"
return "{}<{}>".format(class_name(obj.type), generic)
return class_name(obj.type)
def extra_type_name(typ: str) -> str:
Returns the corresponding Rust type for event's extra key types.
if typ == "boolean":
return "bool"
elif typ == "string":
return "String"
elif typ == "quantity":
return "u32"
def structure_type_name(typ: str) -> str:
Returns the corresponding Rust type for structure items.
if typ == "boolean":
return "bool"
elif typ == "string":
return "String"
elif typ == "number":
return "i64"
def class_name(obj_type):
Returns the Rust class name for a given metric or ping type.
if obj_type == "ping":
return "Ping"
if obj_type.startswith("labeled_"):
obj_type = obj_type[8:]
return util.Camelize(obj_type) + "Metric"
def extra_keys(allowed_extra_keys):
Returns the &'static [&'static str] ALLOWED_EXTRA_KEYS for impl ExtraKeys
return "&[" + ", ".join(map(lambda key: '"' + key + '"', allowed_extra_keys)) + "]"
def get_schedule_reverse_map(objs):
ping_schedule_reverse_map = dict()
if "pings" in objs:
for ping_key, ping_val in objs["pings"].items():
for ping_schedule in ping_val.metadata.get("ping_schedule", []):
if ping_schedule not in ping_schedule_reverse_map:
ping_schedule_reverse_map[ping_schedule] = set()
for ping, schedules in ping_schedule_reverse_map.items():
sorted_schedule = sorted(schedules)
ping_schedule_reverse_map[ping] = sorted_schedule
return ping_schedule_reverse_map
def output_rust(objs, output_fd, ping_names_by_app_id, options={}):
Given a tree of objects, output Rust code to the file-like object `output_fd`.
:param objs: A tree of objects (metrics and pings) as returned from
:param output_fd: Writeable file to write the output to.
:param ping_names_by_app_id: A map of app_ids to lists of ping names.
Used to determine which custom pings to register.
:param options: options dictionary, presently unused.
# Monkeypatch util.snake_case for the templates to use
util.snake_case = lambda value: value.replace(".", "_").replace("-", "_")
# Monkeypatch util.get_jinja2_template to find templates nearby
def get_local_template(template_name, filters=()):
env = jinja2.Environment(
loader=jinja2.PackageLoader("rust", "templates"),
env.filters["camelize"] = util.camelize
env.filters["Camelize"] = util.Camelize
for filter_name, filter_func in filters:
env.filters[filter_name] = filter_func
return env.get_template(template_name)
util.get_jinja2_template = get_local_template
get_metric_id = generate_metric_ids(objs)
get_ping_id = generate_ping_ids(objs)
ping_schedule_reverse_map = get_schedule_reverse_map(objs)
# Map from a tuple (const, typ) to an array of tuples (id, path)
# where:
# const: The Rust constant name to be used for the lookup map
# typ: The metric type to be stored in the lookup map
# id: The numeric metric ID
# path: The fully qualified path to the metric object in Rust
# This map is only filled for metrics, not for pings.
# Example:
# ("COUNTERS", "CounterMetric") -> [(1, "test_only::clicks"), ...]
objs_by_type = {}
# Map from a metric ID to the fully qualified path of the event object in Rust.
# Required for the special handling of event lookups.
# Example:
# 17 -> "test_only::an_event"
events_by_id = {}
# Map from a metric ID to the fully qualified path of the object metric in Rust.
# Required for the special handling of object lookups.
# Example:
# 18 -> "test_only::an_object"
objects_by_id = {}
# Map from a labeled type (e.g. "counter") to a map from metric ID to the
# fully qualified path of the labeled metric object in Rust paired with
# whether the labeled metric has an enum.
# Required for the special handling of labeled metric lookups.
# Example:
# "counter" -> 42 -> ("test_only::mabels_kitchen_counters", false)
labeleds_by_id_by_type = {}
if "pings" in objs:
template_filename = "rust_pings.jinja2"
objs = {"pings": objs["pings"]}
template_filename = "rust.jinja2"
objs = get_metrics(objs)
for category_name, category_value in objs.items():
for metric in category_value.values():
# The constant is all uppercase and suffixed by `_MAP`
const_name = util.snake_case(metric.type).upper() + "_MAP"
typ = type_name(metric)
key = (const_name, typ)
metric_name = util.snake_case(
category_snake = util.snake_case(category_name)
full_path = f"{category_snake}::{metric_name}"
if metric.type == "event":
events_by_id[get_metric_id(metric)] = full_path
if metric.type == "object":
objects_by_id[get_metric_id(metric)] = full_path
if getattr(metric, "labeled", False):
labeled_type = metric.type[8:]
if labeled_type not in labeleds_by_id_by_type:
labeleds_by_id_by_type[labeled_type] = {}
labeleds_by_id_by_type[labeled_type][get_metric_id(metric)] = (
metric.labels and len(metric.labels),
if key not in objs_by_type:
objs_by_type[key] = []
objs_by_type[key].append((get_metric_id(metric), full_path))
# Now for the modules for each category.
template = util.get_jinja2_template(
("rust", rust_datatypes_filter),
("snake_case", util.snake_case),
("type_name", type_name),
("extra_type_name", extra_type_name),
("structure_type_name", structure_type_name),
("ctor", ctor),
("extra_keys", extra_keys),
("metric_id", get_metric_id),
("ping_id", get_ping_id),
submetric_bit=ID_BITS - ID_SIGNAL_BITS,