Add the path of Matplotlib to the link search (for Anaconda)

build.rs

@@ -0,0 +1,30 @@
+use std::{env,
+    fs::File,
+    io::Write,
+    path::Path,
+    process::Command,
+};
+
+fn main() -> Result<(), Box<dyn std::error::Error>> {
+    let outdir = env::var("OUT_DIR")
+        .expect("The OUT_DIR variable must be defined during compilation");
+    let py = Path::new(&outdir).join("matplotlib_location.py");
+    let mut fh = File::create(&py)?;
+    writeln!(fh, "import matplotlib\nprint(matplotlib.__file__)")?;
+    drop(fh);
+
+    let plt_path = Command::new("python3")
+        .arg(py)
+        .output()
+        .expect("Python3 or matplotlib not found.")
+        .stdout;
+    let plt_path = String::from_utf8_lossy(&plt_path);
+    let plt_path = Path::new(plt_path.as_ref());
+
+    if let Some(d) = plt_path.parent() {
+        let d = d.to_str().unwrap();
+        println!("cargo:rustc-link-search={d}");
+        println!("cargo:rustc-env=RUSTFLAGS=-C link-arg=-Wl,-rpath,{d}");
+    }
+    Ok(())
+}

src/lib.rs

@@ -128,7 +128,9 @@ lazy_static! {
 /// ⚠ This may try to lock Python's GIL.  Make sure it is executed
 /// outside a call to `Python::with_gil`.
 macro_rules! pymod { ($m: ident) => {
-    $m.as_ref().map_err(|_| Error::NoMatplotlib)
+    $m.as_ref().map_err(|e| {
+        eprintln!("............... {e}");
+        Error::NoMatplotlib})
 }}