From 27a2e491fa95f7b4872fe926b9234dd9f7e78037 Mon Sep 17 00:00:00 2001
From: katelyn martin <me+cratelyn@katelyn.world>
Date: Tue, 15 Oct 2024 00:00:00 +0000
Subject: [PATCH 1/2] feat(metrics/family): `len()` returns the number of
 metrics

this commit introduces a `len()` method to `Family<S, M, C>`, which
returns the number of series within a metric family.

see also #245, which allows callers to check if a family `contains()` a
given label set.

Signed-off-by: katelyn martin <me+cratelyn@katelyn.world>
---
 src/metrics/family.rs | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/src/metrics/family.rs b/src/metrics/family.rs
index 2f23b198..092378af 100644
--- a/src/metrics/family.rs
+++ b/src/metrics/family.rs
@@ -288,6 +288,28 @@ impl<S: Clone + std::hash::Hash + Eq, M, C: MetricConstructor<M>> Family<S, M, C
         self.metrics.write().clear()
     }
 
+    /// Returns the number of metrics in this family.
+    ///
+    /// ```
+    /// # use prometheus_client::metrics::counter::{Atomic, Counter};
+    /// # use prometheus_client::metrics::family::Family;
+    /// #
+    /// let family = Family::<Vec<(String, String)>, Counter>::default();
+    /// assert_eq!(family.len(), 0);
+    ///
+    /// // Will create the metric with label `method="GET"` on first call and
+    /// // return a reference.
+    /// family.get_or_create(&vec![("method".to_owned(), "GET".to_owned())]).inc();
+    /// assert_eq!(family.len(), 1);
+    ///
+    /// // Clear the family of all label sets.
+    /// family.clear();
+    /// assert_eq!(family.len(), 0);
+    /// ```
+    pub fn len(&self) -> usize {
+        self.metrics.read().len()
+    }
+
     pub(crate) fn read(&self) -> RwLockReadGuard<HashMap<S, M>> {
         self.metrics.read()
     }

From c301225605b5d0464d644492cffc382c3c8d8e77 Mon Sep 17 00:00:00 2001
From: katelyn martin <me+cratelyn@katelyn.world>
Date: Tue, 15 Oct 2024 00:00:00 +0000
Subject: [PATCH 2/2] lint(metrics/family): add `is_empty()`

```shell
$ cargo clippy --all-features --all-targets --tests
   Compiling prometheus-client v0.23.0 (/path/to/prometheus-client)
warning: struct `Family` has a public `len` method, but no `is_empty` method
   --> src/metrics/family.rs:309:5
    |
309 |     pub fn len(&self) -> usize {
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#len_without_is_empty
    = note: `#[warn(clippy::len_without_is_empty)]` on by default

warning: `prometheus-client` (lib) generated 1 warning
warning: `prometheus-client` (lib test) generated 1 warning (1 duplicate)
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.63s
```

Signed-off-by: katelyn martin <me+cratelyn@katelyn.world>
---
 src/metrics/family.rs | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/src/metrics/family.rs b/src/metrics/family.rs
index 092378af..8f4f4721 100644
--- a/src/metrics/family.rs
+++ b/src/metrics/family.rs
@@ -310,6 +310,11 @@ impl<S: Clone + std::hash::Hash + Eq, M, C: MetricConstructor<M>> Family<S, M, C
         self.metrics.read().len()
     }
 
+    /// Returns `true` if the family contains no metrics.
+    pub fn is_empty(&self) -> bool {
+        self.metrics.read().is_empty()
+    }
+
     pub(crate) fn read(&self) -> RwLockReadGuard<HashMap<S, M>> {
         self.metrics.read()
     }