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Fix #8442: pass meta_data to EnsureChannelFirst when track_meta is False #8835

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Fix #8442: pass meta_data to EnsureChannelFirst when track_meta is False #8835

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5 changes: 4 additions & 1 deletion monai/transforms/io/array.py
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Original file line number Diff line number Diff line change
Expand Up @@ -300,7 +300,10 @@ def __call__(self, filename: Sequence[PathLike] | PathLike, reader: ImageReader
img_array, meta_data, self.simple_keys, pattern=self.pattern, sep=self.sep
)
if self.ensure_channel_first:
img = EnsureChannelFirst()(img)
if not isinstance(img, MetaTensor):
img = EnsureChannelFirst()(img, meta_dict=meta_data)
else:
img = EnsureChannelFirst()(img)
Comment on lines 302 to +306
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⚠️ Potential issue | 🟡 Minor

🧩 Analysis chain

🏁 Script executed:

#!/bin/bash
# Description: Check whether tests already cover disabled meta tracking with ensure_channel_first.
# Expect: At least one test combines set_track_meta(False) with ensure_channel_first=True.

rg -n -C3 'set_track_meta\s*\(\s*False\s*\)' --type py
rg -n -C3 'ensure_channel_first\s*=\s*True' --type py

Repository: Project-MONAI/MONAI

Length of output: 18238

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# Find LoadImage/LoadImaged test files
fd -e py "test_load_image" tests/

Repository: Project-MONAI/MONAI

Length of output: 135

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# Search within LoadImage test files for set_track_meta(False) usage
rg -l "class.*LoadImage" tests/ --type py

Repository: Project-MONAI/MONAI

Length of output: 166

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# Check test_load_image.py and test_load_imaged.py for both conditions
for f in tests/transforms/test_load_image.py tests/transforms/test_load_imaged.py; do
  echo "=== $f ==="
  if [ -f "$f" ]; then
    rg -A5 -B5 "ensure_channel_first.*=.*True" "$f" | head -50
    echo "---"
    rg -A5 -B5 "set_track_meta.*False" "$f" | head -50
  fi
done

Repository: Project-MONAI/MONAI

Length of output: 783

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# Read test_load_image.py to check for set_track_meta usage
wc -l tests/transforms/test_load_image.py

Repository: Project-MONAI/MONAI

Length of output: 102

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# Read test_load_imaged.py to check for set_track_meta usage
wc -l tests/transforms/test_load_imaged.py

Repository: Project-MONAI/MONAI

Length of output: 103

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# Check both files for any set_track_meta calls
grep -n "set_track_meta" tests/transforms/test_load_image.py tests/transforms/test_load_imaged.py

Repository: Project-MONAI/MONAI

Length of output: 386

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# Get context around ensure_channel_first usage in both test files
rg -B10 -A10 "ensure_channel_first\s*=\s*True" tests/transforms/test_load_image.py

Repository: Project-MONAI/MONAI

Length of output: 45

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rg -B10 -A10 "ensure_channel_meta_first\s*=\s*True" tests/transforms/test_load_imaged.py

Repository: Project-MONAI/MONAI

Length of output: 45

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# Check lines around set_track_meta in test_load_image.py
sed -n '480,495p' tests/transforms/test_load_image.py

Repository: Project-MONAI/MONAI

Length of output: 734

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# Check lines around set_track_meta in test_load_imaged.py
sed -n '168,185p' tests/transforms/test_load_imaged.py

Repository: Project-MONAI/MONAI

Length of output: 696

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# Search for any ensure_channel_first in test files (case-insensitive)
rg -i "ensure_channel_first" tests/transforms/test_load_image.py tests/transforms/test_load_imaged.py

Repository: Project-MONAI/MONAI

Length of output: 831

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# Find TESTS_META definition in test_load_image.py
rg -B5 -A5 "TESTS_META\s*=" tests/transforms/test_load_image.py

Repository: Project-MONAI/MONAI

Length of output: 347

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# Find TESTS_META definition in test_load_imaged.py
rg -B5 -A5 "TESTS_META\s*=" tests/transforms/test_load_imaged.py

Repository: Project-MONAI/MONAI

Length of output: 444

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# Get the full test_correct test method in test_load_image.py
sed -n '485,510p' tests/transforms/test_load_image.py

Repository: Project-MONAI/MONAI

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# Check if TESTS_META includes ensure_channel_first anywhere
rg -A20 "TESTS_META\s*=" tests/transforms/test_load_image.py | grep "ensure_channel_first"

Repository: Project-MONAI/MONAI

Length of output: 45

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rg -A20 "TESTS_META\s*=" tests/transforms/test_load_imaged.py | grep "ensure_channel_first"

Repository: Project-MONAI/MONAI

Length of output: 45

🏁 Script executed:

# Find all test methods that use ensure_channel_first in test files
rg -B2 "ensure_channel_first" tests/transforms/test_load_image.py tests/transforms/test_load_imaged.py | head -80

Repository: Project-MONAI/MONAI

Length of output: 1457

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# Check if any of those tests also call set_track_meta(False)
rg -B20 "ensure_channel_first\s*=\s*True" tests/transforms/test_load_image.py | rg "set_track_meta"

Repository: Project-MONAI/MONAI

Length of output: 45

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# Check which test method uses TEST_CASE_14, TEST_CASE_18, TEST_CASE_20
rg "TEST_CASE_14|TEST_CASE_18|TEST_CASE_20" tests/transforms/test_load_image.py

Repository: Project-MONAI/MONAI

Length of output: 337

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# Get the test method that uses these test cases
sed -n '445,475p' tests/transforms/test_load_image.py

Repository: Project-MONAI/MONAI

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# Get context around the test_channel_dim method to see full implementation
sed -n '455,480p' tests/transforms/test_load_image.py

Repository: Project-MONAI/MONAI

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# Verify the _cmp method in test_load_imaged.py is not using set_track_meta(False)
sed -n '97,115p' tests/transforms/test_load_imaged.py

Repository: Project-MONAI/MONAI

Length of output: 931

Add regression test for set_track_meta(False) + ensure_channel_first=True.

The fix is correct, but there is no test coverage for set_track_meta(False) combined with LoadImage(..., ensure_channel_first=True) or LoadImaged(..., ensure_channel_first=True). Existing tests cover meta tracking separately from channel-first ordering, but not together. Add a test case to prevent regression of this specific scenario.

🤖 Prompt for AI Agents 
Verify each finding against the current code and only fix it if needed.

In `@monai/transforms/io/array.py` around lines 302 - 306, Add a regression test
that verifies disabling meta tracking with set_track_meta(False) does not break
channel-first conversion when using LoadImage or LoadImaged with
ensure_channel_first=True: create a test that calls set_track_meta(False), runs
LoadImage(..., ensure_channel_first=True) (and a LoadImaged variant) on a sample
array, and asserts the output is channel-first (shape/order) and that no
MetaTensor metadata is attached (or meta dict remains absent) to ensure
EnsureChannelFirst still runs on plain tensors; reference EnsureChannelFirst,
LoadImage/LoadImaged, ensure_channel_first, set_track_meta, and MetaTensor when
locating code to test.

if self.image_only:
return img
return img, img.meta if isinstance(img, MetaTensor) else meta_data
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