fix: improve itk-wasm pipeline error messages shown to users

itk-wasm WASM modules throw raw numeric pointers when they crash,
and stderr output only goes to console.error, not the thrown error.
This made load failures show meaningless numbers or empty messages.

- Wrap readDicomTags errors in handleDicomFile and handleDicomStream
  with human-readable messages, preserving originals as cause
- Check runTask returnValue/stderr for non-crash pipeline failures
- Add getErrorDetail utility for extracting meaningful error messages

Author: PaulHax

src/io/dicom.ts

@@ -47,11 +47,23 @@ async function runTask(
   inputs: any[],
   outputs: any[]
 ) {
-  return runPipeline(module, args, outputs, inputs, {
+  const result = await runPipeline(module, args, outputs, inputs, {
     webWorker: getWorker(),
     pipelineBaseUrl: itkConfig.pipelinesUrl,
     pipelineWorkerUrl: itkConfig.pipelineWorkerUrl,
+  }).catch((error) => {
+    throw new Error(
+      `itk-wasm pipeline "${module}" crashed (check browser console for details)`,
+      { cause: error }
+    );
   });
+  if (result.returnValue !== 0) {
+    const detail = result.stderr?.trim() || 'unknown error';
+    throw new Error(
+      `itk-wasm pipeline "${module}" exited with code ${result.returnValue}: ${detail}`
+    );
+  }
+  return result;
 }
 
 /**

src/io/import/processors/handleDicomFile.ts

@@ -6,6 +6,7 @@ import { ReadDicomTagsFunction } from '@/src/core/streaming/dicom/dicomMetaLoade
 import { ImportHandler, asIntermediateResult } from '@/src/io/import/common';
 import { getWorker } from '@/src/io/itk/worker';
 import { FILE_EXT_TO_MIME } from '@/src/io/mimeTypes';
+import { getErrorDetail } from '@/src/utils';
 import { readDicomTags } from '@itk-wasm/dicom';
 
 /**
@@ -22,8 +23,18 @@ const handleDicomFile: ImportHandler = async (dataSource) => {
   }
 
   const readTags: ReadDicomTagsFunction = async (file) => {
-    const result = await readDicomTags(file, { webWorker: getWorker() });
-    return result.tags;
+    try {
+      const result = await readDicomTags(file, { webWorker: getWorker() });
+      return result.tags;
+    } catch (error) {
+      const detail = getErrorDetail(
+        error,
+        'the file could not be parsed as valid DICOM (check browser console for details)'
+      );
+      throw new Error(`Failed to read DICOM tags: ${detail}`, {
+        cause: error,
+      });
+    }
   };
 
   const metaLoader = new DicomFileMetaLoader(dataSource.file, readTags);

src/io/import/processors/handleDicomStream.ts

@@ -14,6 +14,7 @@ import {
 } from '@/src/io/import/common';
 import { getWorker } from '@/src/io/itk/worker';
 import { FILE_EXT_TO_MIME } from '@/src/io/mimeTypes';
+import { getErrorDetail } from '@/src/utils';
 import { readDicomTags } from '@itk-wasm/dicom';
 import { Tags } from '@/src/core/dicomTags';
 import { useMessageStore } from '@/src/store/messages';
@@ -34,8 +35,13 @@ const handleDicomStream: ImportHandler = async (dataSource) => {
       const result = await readDicomTags(file, { webWorker: getWorker() });
       return result.tags;
     } catch (error) {
+      const detail = getErrorDetail(
+        error,
+        'the file could not be parsed as valid DICOM (check browser console for details)'
+      );
       throw new Error(
-        `Failed to read DICOM tags from ${dataSource.uri}: ${error}`
+        `Failed to read DICOM tags from ${dataSource.uri}: ${detail}`,
+        { cause: error }
       );
     }
   };

src/utils/index.ts

@@ -215,6 +215,10 @@ export function ensureError(e: unknown) {
   return e instanceof Error ? e : new Error(JSON.stringify(e));
 }
 
+export function getErrorDetail(error: unknown, fallback: string): string {
+  return error instanceof Error && error.message ? error.message : fallback;
+}
+
 // remove undefined properties
 export function cleanUndefined(obj: Object) {
   return Object.entries(obj).reduce(