Fix frame cleanup race, value0 guard, and clean up warnings imports

renderer.py:
- Use tempfile.mkdtemp instead of hardcoded _frames/ dir to prevent
  concurrent-run conflicts when two instances render to the same output dir
- Always clean up temporary frame files (move cleanup into finally block
  so frames are removed even if imageio write fails)

silo_reader.py:
- Add guard for missing 'value0' key in Silo attr (avoids cryptic KeyError
  on malformed Silo files; emits a warning and skips the variable)
- Move `import warnings` to module scope (remove duplicate inline imports)

reader.py:
- Move `import warnings` to module scope (remove duplicate inline imports)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: sbryngelson

toolchain/mfc/viz/reader.py

@@ -13,6 +13,7 @@
 
 import os
 import struct
+import warnings
 from dataclasses import dataclass, field
 from typing import Dict, List, Optional, Tuple
 
@@ -395,12 +396,10 @@ def assemble(case_dir: str, step: int, fmt: str = 'binary',  # pylint: disable=t
     for rank in ranks:
         fpath = os.path.join(case_dir, 'binary', f'p{rank}', f'{step}.dat')
         if not os.path.isfile(fpath):
-            import warnings  # pylint: disable=import-outside-toplevel
             warnings.warn(f"Processor file not found, skipping: {fpath}", stacklevel=2)
             continue
         pdata = read_binary_file(fpath, var_filter=var)
         if pdata.m == 0 and pdata.n == 0 and pdata.p == 0:
-            import warnings  # pylint: disable=import-outside-toplevel
             warnings.warn(f"Processor p{rank} has zero dimensions, skipping", stacklevel=2)
             continue
         proc_data.append((rank, pdata))

toolchain/mfc/viz/renderer.py

@@ -7,9 +7,9 @@
 """
 
 import os
+import tempfile
 
 import numpy as np
-
 import matplotlib
 matplotlib.use('Agg')
 import matplotlib.pyplot as plt  # pylint: disable=wrong-import-position
@@ -197,18 +197,10 @@ def render_mp4(varname, steps, output, fps=10,  # pylint: disable=too-many-argum
         if auto_vmax is None and all_maxs:
             opts['vmax'] = max(all_maxs)
 
-    # Write frames as images to a temp directory next to the output file
+    # Write frames to a unique temp directory to avoid concurrent-run conflicts
     output_dir = os.path.dirname(os.path.abspath(output))
-    viz_dir = os.path.join(output_dir, '_frames')
-    # Clean stale frames from any interrupted previous run
-    if os.path.isdir(viz_dir):
-        for stale in os.listdir(viz_dir):
-            if stale.endswith('.png'):
-                try:
-                    os.remove(os.path.join(viz_dir, stale))
-                except OSError:
-                    pass
-    os.makedirs(viz_dir, exist_ok=True)
+    os.makedirs(output_dir, exist_ok=True)
+    viz_dir = tempfile.mkdtemp(dir=output_dir, prefix='_frames_')
 
     try:
         from tqdm import tqdm  # pylint: disable=import-outside-toplevel
@@ -246,7 +238,6 @@ def render_mp4(varname, steps, output, fps=10,  # pylint: disable=too-many-argum
         import imageio  # pylint: disable=import-outside-toplevel
     except ImportError:
         print("imageio is not installed. Install it with: pip install imageio imageio-ffmpeg")
-        print(f"Frames saved to {viz_dir}/")
         return False
 
     writer = None
@@ -261,17 +252,14 @@ def render_mp4(varname, steps, output, fps=10,  # pylint: disable=too-many-argum
     finally:
         if writer is not None:
             writer.close()
-
-    # Clean up only the frames we created
-    if success:
+        # Always clean up temporary frame files
         for fname in frame_files:
-            fpath = os.path.join(viz_dir, fname)
             try:
-                os.remove(fpath)
+                os.remove(os.path.join(viz_dir, fname))
             except OSError:
                 pass
         try:
             os.rmdir(viz_dir)
         except OSError:
-            pass  # directory not empty (pre-existing files)
+            pass
     return success

toolchain/mfc/viz/silo_reader.py

@@ -12,6 +12,7 @@
 """
 
 import os
+import warnings
 from typing import Dict, List, Optional, Tuple
 
 import numpy as np
@@ -115,7 +116,10 @@ def read_silo_file(  # pylint: disable=too-many-locals
             if "silo" not in obj.attrs:
                 continue
             attr = obj.attrs["silo"]
-            data_path = attr["value0"]
+            data_path = attr.get("value0")
+            if data_path is None:
+                warnings.warn(f"Variable '{key}' missing 'value0' in silo attr, skipping", stacklevel=2)
+                continue
             data = _resolve_path(f, data_path).astype(np.float64)
 
             # MFC's DBPUTQV1 passes the Fortran column-major array as a
@@ -160,7 +164,6 @@ def assemble_silo(
     for rank in ranks:
         silo_file = os.path.join(base, f"p{rank}", f"{step}.silo")
         if not os.path.isfile(silo_file):
-            import warnings  # pylint: disable=import-outside-toplevel
             warnings.warn(f"Processor file not found, skipping: {silo_file}", stacklevel=2)
             continue
         pdata = read_silo_file(silo_file, var_filter=var)