wasi-nn: add testing module

This testing-only module has code (i.e., `check_test!`) to check whether
OpenVINO and some test artifacts are available. The test artifacts are
downloaded and cached if not present, expecting `curl` to be present on
the command line (as discussed in the previous version of this, bytecodealliance#6895).

crates/wasi-nn/src/lib.rs

@@ -6,6 +6,7 @@ pub use ctx::{preload, WasiNnCtx};
 pub use registry::{GraphRegistry, InMemoryRegistry};
 pub mod wit;
 pub mod witx;
+pub mod testing;
 
 use std::sync::Arc;
 

crates/wasi-nn/src/testing.rs

@@ -0,0 +1,91 @@
+//! This is testing-specific code--it is public only so that it can be
+//! accessible both in unit and integration tests.
+//!
+//! This module checks:
+//! - that OpenVINO can be found in the environment
+//! - that some ML model artifacts can be downloaded and cached.
+
+use anyhow::{anyhow, Context, Result};
+use std::{env, fs, path::Path, path::PathBuf, process::Command};
+
+/// Return the directory in which the test artifacts are stored.
+pub fn artifacts_dir() -> PathBuf {
+    PathBuf::from(env!("OUT_DIR")).join("mobilenet")
+}
+
+/// Early-return from a test if the test environment is not met. If the `CI`
+/// or `FORCE_WASINN_TEST_CHECK` environment variables are set, though, this
+/// will return an error instead.
+#[macro_export]
+macro_rules! check_test {
+    () => {
+        if let Err(e) = $crate::testing::check() {
+            if std::env::var_os("CI").is_some()
+                || std::env::var_os("FORCE_WASINN_TEST_CHECK").is_some()
+            {
+                return Err(e);
+            } else {
+                println!("> ignoring test: {}", e);
+                return Ok(());
+            }
+        }
+    };
+}
+
+/// Return `Ok` if all checks pass.
+pub fn check() -> Result<()> {
+    check_openvino_is_installed()?;
+    check_openvino_artifacts_are_available()?;
+    Ok(())
+}
+
+/// Return `Ok` if we find a working OpenVINO installation.
+fn check_openvino_is_installed() -> Result<()> {
+    match std::panic::catch_unwind(|| println!("> found openvino version: {}", openvino::version()))
+    {
+        Ok(_) => Ok(()),
+        Err(e) => Err(anyhow!("unable to find an OpenVINO installation: {:?}", e)),
+    }
+}
+
+/// Return `Ok` if we find the cached MobileNet test artifacts; this will
+/// download the artifacts if necessary.
+fn check_openvino_artifacts_are_available() -> Result<()> {
+    const BASE_URL: &str =
+        "https://github.com/intel/openvino-rs/raw/main/crates/openvino/tests/fixtures/mobilenet";
+    let artifacts_dir = artifacts_dir();
+    if !artifacts_dir.is_dir() {
+        fs::create_dir(&artifacts_dir)?;
+    }
+    for (from, to) in [
+        ("mobilenet.bin", "model.bin"),
+        ("mobilenet.xml", "model.xml"),
+        ("tensor-1x224x224x3-f32.bgr", "tensor.bgr"),
+    ] {
+        let remote_url = [BASE_URL, from].join("/");
+        let local_path = artifacts_dir.join(to);
+        if !local_path.is_file() {
+            download(&remote_url, &local_path)
+                .with_context(|| "unable to retrieve test artifact")?;
+        } else {
+            println!("> using cached artifact: {}", local_path.display())
+        }
+    }
+    Ok(())
+}
+
+/// Retrieve the bytes at the `from` URL and place them in the `to` file.
+fn download(from: &str, to: &Path) -> anyhow::Result<()> {
+    let mut curl = Command::new("curl");
+    curl.arg("--location").arg(from).arg("--output").arg(to);
+    println!("> downloading: {:?}", &curl);
+    let result = curl.output().unwrap();
+    if !result.status.success() {
+        panic!(
+            "curl failed: {}\n{}",
+            result.status,
+            String::from_utf8_lossy(&result.stderr)
+        );
+    }
+    Ok(())
+}