Bug 1632131 - Simple smoke test for FOG's string metric type. r=chutten

A first Rust test, which should run without any interaction with
Firefox.
This will eventually break down when we get IPC in there.

Depends on D72128

Differential Revision: https://phabricator.services.mozilla.com/D72385

toolkit/components/glean/api/Cargo.toml

@@ -8,3 +8,7 @@ publish = false
 [dependencies]
 glean-core = "25.1.0"
 log = "0.4"
+once_cell = "1.2.0"
+
+[dev-dependencies]
+tempfile = "3.1.0"

toolkit/components/glean/api/src/lib.rs

@@ -10,6 +10,9 @@
 //! assert!(glean::is_upload_enabled())
 //! ```
 
+// Re-exporting for later use in generated code.
+pub extern crate once_cell;
+
 pub mod metrics;
 
 /// Run a closure with a mutable reference to the locked global Glean object.

toolkit/components/glean/api/tests/common/mod.rs

@@ -0,0 +1,40 @@
+// 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 https://mozilla.org/MPL/2.0/.
+
+use std::sync::{Mutex, MutexGuard};
+
+use glean::once_cell::sync::Lazy;
+
+const GLOBAL_APPLICATION_ID: &str = "org.mozilla.firefox.test";
+
+/// UGLY HACK.
+/// We use a global lock to force synchronization of all tests, even if run multi-threaded.
+/// This allows us to run without `--test-threads 1`.`
+pub fn lock_test() -> MutexGuard<'static, ()> {
+    static GLOBAL_LOCK: Lazy<Mutex<()>> = Lazy::new(|| Mutex::new(()));
+
+    GLOBAL_LOCK.lock().unwrap()
+}
+
+// Create a new instance of Glean with a temporary directory.
+// We need to keep the `TempDir` alive, so that it's not deleted before we stop using it.
+pub fn setup_glean(tempdir: Option<tempfile::TempDir>) -> tempfile::TempDir {
+    let dir = match tempdir {
+        Some(tempdir) => tempdir,
+        None => tempfile::tempdir().unwrap(),
+    };
+    let tmpname = dir.path().display().to_string();
+
+    let cfg = glean_core::Configuration {
+        data_path: tmpname,
+        application_id: GLOBAL_APPLICATION_ID.into(),
+        upload_enabled: true,
+        max_events: None,
+        delay_ping_lifetime_io: false,
+    };
+    let glean = glean_core::Glean::new(cfg).unwrap();
+    glean_core::setup_glean(glean).expect("can't set up global Glean object");
+
+    dir
+}

toolkit/components/glean/api/tests/string.rs

@@ -0,0 +1,27 @@
+mod common;
+use common::*;
+
+use glean::metrics::{CommonMetricData, Lifetime, StringMetric};
+
+#[test]
+fn sets_string_value() {
+    let _lock = lock_test();
+    let _t = setup_glean(None);
+    let store_names: Vec<String> = vec!["store1".into()];
+
+    let metric = StringMetric::new(CommonMetricData {
+        name: "string_metric".into(),
+        category: "telemetry".into(),
+        send_in_pings: store_names.clone(),
+        disabled: false,
+        lifetime: Lifetime::Ping,
+        ..Default::default()
+    });
+
+    metric.set("test_string_value");
+
+    assert_eq!(
+        "test_string_value",
+        metric.test_get_value("store1").unwrap()
+    );
+}

toolkit/library/rust/moz.build

@@ -11,6 +11,7 @@ RustLibrary('gkrust', gkrust_features, is_gkrust=True)
 # Target directory doesn't matter a lot here, since we can't share panic=abort
 # compilation artifacts with gkrust.
 RUST_TESTS = [
+    'glean',
     'selectors',
     'servo_arc',
     'stylo_tests',