From 18e9be0af7a6a781fe4c394f45bed37a6472bfa3 Mon Sep 17 00:00:00 2001
From: osobh <om.sobh@gmail.com>
Date: Sun, 27 Sep 2026 07:57:49 -0500
Subject: [PATCH] py: only well-formed masks are NotImplementedError; others
 stay TypeError

A boolean array of the axis's length, or of the dataset's whole shape, is
a mask h5py would apply (NotImplementedError here); one of any other shape
(np.array(True), a wrong length) is a key h5py itself refuses with
TypeError, which test_errors_match_h5py requires us to match.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
---
 crates/clawhdf5-py/src/select.rs | 28 ++++++++++++++++++++++++----
 1 file changed, 24 insertions(+), 4 deletions(-)

diff --git a/crates/clawhdf5-py/src/select.rs b/crates/clawhdf5-py/src/select.rs
index 93a1ad1..88ac358 100644
--- a/crates/clawhdf5-py/src/select.rs
+++ b/crates/clawhdf5-py/src/select.rs
@@ -255,6 +255,17 @@ pub(crate) fn parse(key: &Bound<'_, PyAny>, dims: &[u64]) -> PyResult<Plan> {
         }
     }
 
+    // A mask of the dataset's whole shape (`ds[ds[()] > 0]`).
+    if let [a] = args.as_slice() {
+        let np = key.py().import("numpy")?;
+        if a.is_instance(&np.getattr("ndarray")?)?
+            && a.getattr("dtype")?.getattr("kind")?.extract::<String>()? == "b"
+            && a.getattr("ndim")?.extract::<usize>()? > 1
+            && a.getattr("shape")?.extract::<Vec<u64>>()? == dims
+        {
+            return Err(mask_unsupported());
+        }
+    }
     if args.iter().any(|a| a.is_none()) {
         return Err(PyTypeError::new_err(
             "Indexing with None (or np.newaxis) is not supported",
@@ -333,6 +344,10 @@ pub(crate) fn parse(key: &Bound<'_, PyAny>, dims: &[u64]) -> PyResult<Plan> {
     })
 }
 
+fn mask_unsupported() -> PyErr {
+    PyNotImplementedError::new_err("boolean mask indexing is not supported by clawhdf5")
+}
+
 fn parse_axis(py: Python<'_>, a: &Bound<'_, PyAny>, n: u64) -> PyResult<Axis> {
     if a.is_none() {
         return Err(PyTypeError::new_err(
@@ -380,10 +395,15 @@ fn parse_axis(py: Python<'_>, a: &Bound<'_, PyAny>, n: u64) -> PyResult<Axis> {
         let arr = np.call_method1("asarray", (a,))?;
         let kind: String = arr.getattr("dtype")?.getattr("kind")?.extract()?;
         if kind == "b" {
-            // h5py supports masks; clawhdf5 does not (yet), for reads or
-            // writes: an unsupported operation, not a wrong key.
-            return Err(PyNotImplementedError::new_err(
-                "boolean mask indexing is not supported by clawhdf5",
+            // A mask along this axis (h5py supports them; clawhdf5 does
+            // not, for reads or writes: an unsupported operation). A mask
+            // of any other shape is a wrong key, as in h5py.
+            let shape: Vec<u64> = arr.getattr("shape")?.extract()?;
+            if shape == [n] {
+                return Err(mask_unsupported());
+            }
+            return Err(PyTypeError::new_err(
+                "Boolean indexing array has incompatible shape",
             ));
         }
         let ndim: usize = arr.getattr("ndim")?.extract()?;