feat(registry): add with_prefix_and_labels constructor (#147)

Signed-off-by: Adrian Pop <[email protected]>

CHANGELOG.md

@@ -4,6 +4,18 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [0.21.2]
+
+### Added
+
+- Added `sub_registry_with_labels` method to `Registry`.
+  See [PR 145].
+- Added `with_labels` and `with_prefix_and_labels` constructors to `Registry`.
+  See [PR 147].
+
+[PR 145]: https://github.com/prometheus/client_rust/pull/145
+[PR 147]: https://github.com/prometheus/client_rust/pull/147
+
 ## [0.21.1]
 
 ### Added

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "prometheus-client"
-version = "0.21.1"
+version = "0.21.2"
 authors = ["Max Inden <[email protected]>"]
 edition = "2021"
 description = "Open Metrics client library allowing users to natively instrument applications."

src/registry.rs

@@ -75,6 +75,28 @@ impl Registry {
         }
     }
 
+    /// Creates a new default [`Registry`] with the given labels.
+    pub fn with_labels(
+        labels: impl Iterator<Item = (Cow<'static, str>, Cow<'static, str>)>,
+    ) -> Self {
+        Self {
+            labels: labels.into_iter().collect(),
+            ..Default::default()
+        }
+    }
+
+    /// Creates a new default [`Registry`] with the given prefix and labels.
+    pub fn with_prefix_and_labels(
+        prefix: impl Into<String>,
+        labels: impl Iterator<Item = (Cow<'static, str>, Cow<'static, str>)>,
+    ) -> Self {
+        Self {
+            prefix: Some(Prefix(prefix.into())),
+            labels: labels.into_iter().collect(),
+            ..Default::default()
+        }
+    }
+
     /// Register a metric with the [`Registry`].
     ///
     /// Note: In the Open Metrics text exposition format some metric types have
@@ -527,6 +549,53 @@ mod tests {
     use super::*;
     use crate::metrics::counter::Counter;
 
+    #[test]
+    fn constructors() {
+        let counter_name = "test_counter";
+        let prefix = "test_prefix";
+        let labels = vec![
+            (Cow::Borrowed("global_label_1"), Cow::Borrowed("value_1")),
+            (Cow::Borrowed("global_label_1"), Cow::Borrowed("value_2")),
+        ];
+        // test with_prefix constructor
+        let mut registry = Registry::with_prefix(prefix);
+        let counter: Counter = Counter::default();
+        registry.register(counter_name, "some help", counter);
+
+        assert_eq!(
+            Some((prefix.to_string() + "_" + counter_name, vec![])),
+            registry
+                .iter_metrics()
+                .map(|(desc, _)| (desc.name.clone(), desc.labels.clone()))
+                .next()
+        );
+
+        // test with_labels constructor
+        let mut registry = Registry::with_labels(labels.clone().into_iter());
+        let counter: Counter = Counter::default();
+        registry.register(counter_name, "some help", counter);
+        assert_eq!(
+            Some((counter_name.to_string(), labels.clone())),
+            registry
+                .iter_metrics()
+                .map(|(desc, _)| (desc.name.clone(), desc.labels.clone()))
+                .next()
+        );
+
+        // test with_prefix_and_labels constructor
+        let mut registry = Registry::with_prefix_and_labels(prefix, labels.clone().into_iter());
+        let counter: Counter = Counter::default();
+        registry.register(counter_name, "some help", counter);
+
+        assert_eq!(
+            Some((prefix.to_string() + "_" + counter_name, labels)),
+            registry
+                .iter_metrics()
+                .map(|(desc, _)| (desc.name.clone(), desc.labels.clone()))
+                .next()
+        );
+    }
+
     #[test]
     fn register_and_iterate() {
         let mut registry = Registry::default();