Add dummy feature for non supported platforms

.github/workflows/audit.yml

@@ -12,7 +12,7 @@ jobs:
   security_audit:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: actions/cache@v3
         with:
           path: |

.github/workflows/build.yml

@@ -9,7 +9,7 @@ jobs:
         runner: [ubuntu-latest, macos-latest, windows-latest]
     runs-on: ${{ matrix.runner }}
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: actions/cache@v3
         with:
           path: |
@@ -29,3 +29,32 @@ jobs:
       - name: Test
         run: |
           cargo build --release --all-features
+
+  build-dummy:
+    strategy:
+      matrix:
+        # Targets that this crate does NOT support
+        target: [x86_64-unknown-freebsd]
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/cache@v3
+        with:
+          path: |
+            ~/.cargo/bin/
+            ~/.cargo/registry/index/
+            ~/.cargo/registry/cache/
+            ~/.cargo/git/db/
+            target/
+          key: ${{ runner.os }}-cargo-${{ hashFiles('**/Cargo.lock') }}
+      - name: Update local toolchain
+        run: |
+          rustup update
+          rustup target add ${{ matrix.target }}
+      - name: Toolchain info
+        run: |
+          rustc --version
+          cargo --version --verbose
+      - name: Test
+        run: |
+          cargo build --release --features dummy --target ${{ matrix.target }}

.github/workflows/test.yml

@@ -6,7 +6,7 @@ jobs:
   fmt:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: actions/cache@v3
         with:
           path: |
@@ -32,7 +32,7 @@ jobs:
   check:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: actions/cache@v3
         with:
           path: |
@@ -63,7 +63,7 @@ jobs:
       RUNNER: ${{ matrix.runner }}
     runs-on: ${{ matrix.runner }}
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: actions/cache@v3
         with:
           path: |

Cargo.toml

@@ -13,6 +13,10 @@ keywords = [ "cross-platform", "metrics", "prometheus", "open-metrics", "process
 [package.metadata.docs.rs]
 all-features = true
 
+[features]
+# Enable a `dummy` collector that always return an empty `Metrics` for non supported platforms
+dummy = []
+
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]

README.md

@@ -48,6 +48,10 @@ Go ([client_golang]) provides.
 | `process_start_time_seconds`       | x     | x     | x       |
 | `process_threads`                  | x     | x     |         |
 
+Please note that if you only need to compile this crate on non-supported
+platforms, you can use the `dummy` feature. Enabling this feature activates a
+dummy collector, which returns an empty `Metrics`.
+
 [client_golang]: https://github.com/prometheus/client_golang
 
 ## Usage
@@ -115,6 +119,14 @@ async fn main() {
 }
 ```
 
+## Features
+
+This crate offers the following features:
+
+| Feature Name | Description                                                                           |
+| ------------ | ------------------------------------------------------------------------------------- |
+| `dummy`      | Enables a dummy collector that returns an empty `Metrics` on non-supported platforms. |
+
 ## Difference from [metrics-process-promstyle]
 
 It appears that [metrics-process-promstyle] only supports Linux, but this crate

src/collector.rs

@@ -1,12 +1,19 @@
-#[cfg(target_os = "macos")]
-mod macos;
+#[cfg_attr(target_os = "macos", path = "collector/macos.rs")]
+#[cfg_attr(target_os = "linux", path = "collector/linux.rs")]
+#[cfg_attr(target_os = "windows", path = "collector/windows.rs")]
+#[allow(unused_attributes)]
+#[cfg_attr(feature = "dummy", path = "collector/dummy.rs")]
+mod collector;
 
-#[cfg(target_os = "linux")]
-mod linux;
+#[cfg(all(
+    not(feature = "dummy"),
+    not(any(target_os = "macos", target_os = "linux", target_os = "windows"))
+))]
+compile_error!(
+    "A feature \"dummy\" must be enabled to compile this crate on non supported platforms."
+);
 
-#[cfg(target_os = "windows")]
-#[path = "collector/windows.rs"]
-mod win;
+pub use collector::collect;
 
 /// Process metrics
 /// https://prometheus.io/docs/instrumenting/writing_clientlibs/#process-metrics
@@ -32,15 +39,6 @@ pub struct Metrics {
     pub threads: Option<u64>,
 }
 
-#[cfg(target_os = "macos")]
-pub use macos::collect;
-
-#[cfg(target_os = "linux")]
-pub use linux::collect;
-
-#[cfg(target_os = "windows")]
-pub use win::collect;
-
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -54,6 +52,7 @@ mod tests {
         }
     }
 
+    #[cfg(any(target_os = "macos", target_os = "linux", target_os = "windows"))]
     #[test]
     fn test_collect_internal_ok() {
         fibonacci(40);
@@ -70,4 +69,23 @@ mod tests {
         #[cfg(not(target_os = "windows"))]
         assert_matches!(m.threads, Some(_));
     }
+
+    #[cfg(not(target_os = "macos"))]
+    #[cfg(not(target_os = "linux"))]
+    #[cfg(not(target_os = "windows"))]
+    #[cfg(feature = "dummy")]
+    #[test]
+    fn test_collect_internal_ok_dummy() {
+        fibonacci(40);
+        let m = collect();
+        dbg!(&m);
+        assert_matches!(m.cpu_seconds_total, None);
+        assert_matches!(m.open_fds, None);
+        assert_matches!(m.max_fds, None);
+        assert_matches!(m.virtual_memory_bytes, None);
+        assert_matches!(m.virtual_memory_max_bytes, None);
+        assert_matches!(m.resident_memory_bytes, None);
+        assert_matches!(m.start_time_seconds, None);
+        assert_matches!(m.threads, None);
+    }
 }

src/collector/dummy.rs

@@ -0,0 +1,5 @@
+use super::Metrics;
+
+pub fn collect() -> Metrics {
+    Metrics::default()
+}