Carry the extraction failure code into the indexer

app/MindWork AI Studio/Tools/FileExtractionErrorCodeExtensions.cs

@@ -0,0 +1,95 @@
+using AIStudio.Tools.PluginSystem;
+
+namespace AIStudio.Tools;
+
+/// <summary>
+/// Tells failures which lie in the file apart from failures which lie in its surroundings, and
+/// puts both into words for the indexing user interface.
+/// </summary>
+/// <remarks>
+/// A file without readable text fails the same way on every run, so the indexer remembers it and
+/// waits for the file to change. An offline network drive or an overloaded provider says nothing
+/// about the file itself, which is why those keep being retried.
+/// </remarks>
+internal static class FileExtractionErrorCodeExtensions
+{
+    private static string TB(string fallbackEN) => I18N.I.T(fallbackEN, typeof(FileExtractionErrorCodeExtensions).Namespace, nameof(FileExtractionErrorCodeExtensions));
+
+    /// <summary>
+    /// Gets a value indicating whether reading the file again will fail again, as long as the file
+    /// itself does not change.
+    /// </summary>
+    /// <param name="code">The stable failure code.</param>
+    /// <returns>True, when the reason lies in the file itself.</returns>
+    internal static bool IsPermanentIndexingFailure(this FileExtractionErrorCode code) => code switch
+    {
+        //
+        // The reason lies in the file. Reading it again without changing it produces the same
+        // outcome, so the indexer waits for a new fingerprint:
+        //
+        FileExtractionErrorCode.NO_TEXT_EXTRACTED => true,
+        FileExtractionErrorCode.NO_CONTENT => true,
+        FileExtractionErrorCode.NOT_TEXT_CONTENT => true,
+        FileExtractionErrorCode.NOT_A_VALID_PDF => true,
+        FileExtractionErrorCode.NOT_A_VALID_SPREADSHEET => true,
+        FileExtractionErrorCode.PDF_ENCRYPTED => true,
+        FileExtractionErrorCode.FORMAT_DETECTION_FAILED => true,
+        FileExtractionErrorCode.EXECUTABLE_REJECTED => true,
+        FileExtractionErrorCode.UNSUPPORTED => true,
+
+        // Pages holding nothing but images are one of the recurring cases here, and that is a
+        // property of the document, not of the environment:
+        FileExtractionErrorCode.PAGE_EXTRACTION_FAILED => true,
+
+        //
+        // Everything else depends on the surroundings: an unavailable drive, a file someone else
+        // has open, a missing engine, or a runtime which did not answer in time. All of them are
+        // worth another attempt during the next run:
+        //
+        _ => false,
+    };
+
+    /// <summary>
+    /// Gets the localized message which explains why a file was not indexed.
+    /// </summary>
+    /// <remarks>
+    /// These texts are the counterpart of the ones used for chat attachments: there, a file which
+    /// cannot be read is simply not sent, while here it stays out of the index and the user needs
+    /// to know whether AI Studio will come back to it on its own.
+    /// </remarks>
+    /// <param name="code">The stable failure code.</param>
+    /// <param name="fileName">The name of the file, as shown to the user.</param>
+    /// <returns>The localized message.</returns>
+    internal static string ToIndexingUserMessage(this FileExtractionErrorCode code, string fileName) => string.Format(ToIndexingMessageFormat(code), fileName);
+
+    private static string ToIndexingMessageFormat(FileExtractionErrorCode code) => code switch
+    {
+        //
+        // Permanent failures. Each of them names what is wrong with the file and says that AI
+        // Studio comes back to it once the file changes:
+        //
+        FileExtractionErrorCode.NO_TEXT_EXTRACTED => TB("No text could be read from the file '{0}', so it was not indexed. It might contain images only, such as a scanned PDF without a text layer. AI Studio reads it again as soon as the file changes."),
+        FileExtractionErrorCode.NO_CONTENT => TB("The file '{0}' did not provide any content, so it was not indexed. AI Studio reads it again as soon as the file changes."),
+        FileExtractionErrorCode.NOT_TEXT_CONTENT => TB("The file '{0}' is not a text file, so it was not indexed. Its content could not be read as text, which means it might have a wrong file extension. AI Studio reads it again as soon as the file changes."),
+        FileExtractionErrorCode.NOT_A_VALID_PDF => TB("The file '{0}' is not a readable PDF, so it was not indexed. It might be damaged or transferred incompletely. AI Studio reads it again as soon as the file changes."),
+        FileExtractionErrorCode.NOT_A_VALID_SPREADSHEET => TB("The file '{0}' is not a readable spreadsheet, so it was not indexed. It might be damaged or transferred incompletely. AI Studio reads it again as soon as the file changes."),
+        FileExtractionErrorCode.PDF_ENCRYPTED => TB("The file '{0}' is protected and could not be opened, so it was not indexed. AI Studio reads it again as soon as the file changes."),
+        FileExtractionErrorCode.FORMAT_DETECTION_FAILED => TB("The file type of '{0}' could not be determined, so the file was not indexed. AI Studio reads it again as soon as the file changes."),
+        FileExtractionErrorCode.EXECUTABLE_REJECTED => TB("The file '{0}' is an executable program and was not indexed, regardless of its file extension."),
+        FileExtractionErrorCode.UNSUPPORTED => TB("The file type of '{0}' is not supported, so the file was not indexed. AI Studio reads it again as soon as the file changes."),
+        FileExtractionErrorCode.PAGE_EXTRACTION_FAILED => TB("Pages of the file '{0}' could not be read, so it was not indexed. They might contain images only. AI Studio reads it again as soon as the file changes."),
+
+        //
+        // Temporary failures. They name what the user can act on, and every one of them is tried
+        // again during the next run:
+        //
+        FileExtractionErrorCode.FILE_NOT_FOUND => TB("The file '{0}' does not exist anymore and was not indexed."),
+        FileExtractionErrorCode.FILE_NOT_READABLE => TB("The file '{0}' could not be read and was not indexed. When the file is stored on a network drive, the drive might be unavailable, or another program might be blocking the file. AI Studio tries again during the next run."),
+        FileExtractionErrorCode.FILE_LOCKED => TB("The file '{0}' is currently open in another program, which is why it was not indexed. When the file is stored on a shared network drive, a colleague might have it open. AI Studio tries again during the next run."),
+        FileExtractionErrorCode.TIMEOUT => TB("Reading the file '{0}' took too long and was stopped, so the file was not indexed. When the file is stored on a network drive, the connection might be slow or interrupted. AI Studio tries again during the next run."),
+        FileExtractionErrorCode.PDFIUM_UNAVAILABLE => TB("AI Studio was not able to start its PDF engine, so the file '{0}' was not indexed. AI Studio tries again during the next run."),
+        FileExtractionErrorCode.PANDOC_UNAVAILABLE => TB("Reading the file '{0}' needs Pandoc, which is not available, so the file was not indexed. AI Studio tries again during the next run."),
+
+        _ => TB("The file '{0}' could not be read and was not indexed. AI Studio tries again during the next run."),
+    };
+}

app/MindWork AI Studio/Tools/FileExtractionException.cs

@@ -0,0 +1,27 @@
+namespace AIStudio.Tools;
+
+/// <summary>
+/// Thrown when a file could not be read, carrying the stable failure code along with the message.
+/// </summary>
+/// <remarks>
+/// The plain message alone does not say whether another attempt is worth anything. The code does,
+/// which is what the indexer needs to tell a file without readable text apart from a network drive
+/// which happens to be offline.
+/// </remarks>
+public sealed class FileExtractionException(FileExtractionErrorCode code, string message, int? pageNumber = null, string? detectedFormat = null) : Exception(message)
+{
+    /// <summary>
+    /// Gets the stable failure code.
+    /// </summary>
+    public FileExtractionErrorCode Code { get; } = code;
+
+    /// <summary>
+    /// Gets the page the failure belongs to, when the failure affects a single page only.
+    /// </summary>
+    public int? PageNumber { get; } = pageNumber;
+
+    /// <summary>
+    /// Gets the format the runtime identified by looking at the content.
+    /// </summary>
+    public string? DetectedFormat { get; } = detectedFormat;
+}

app/MindWork AI Studio/Tools/Services/DataSourceEmbeddingService.cs

@@ -769,8 +769,13 @@ public sealed partial class DataSourceEmbeddingService(SettingsManager settingsM
         if (batch.Count > 0)
             await this.FlushBatchAsync(indexStore, vectorStore, dataSource, file, fingerprint, parentFile, embeddingProvider, provider, manifest, optimizationTracker, collectionName, batch, token);
 
+        //
+        // The extraction itself did not report a failure, but nothing usable came out of it. For
+        // the index this is the same case as a scanned page without a text layer, which is why it
+        // carries a code of its own instead of an unclassified exception:
+        //
         if (totalChunkCount == 0)
-            throw new InvalidOperationException(string.Format(TB("No text could be read from the file '{0}'."), file.Name));
+            throw new FileExtractionException(FileExtractionErrorCode.NO_CONTENT, string.Format(TB("No text could be read from the file '{0}'."), file.Name));
 
         logger.LogDebug(
             "Generated {ChunkCount} chunks for file '{FilePath}' in data source '{DataSourceName}' ({DataSourceId}).",

app/MindWork AI Studio/Tools/Services/RustService.Retrieval.cs

@@ -372,7 +372,7 @@ public sealed partial class RustService
                         error.DetectedFormat,
                         error.Message);
 
-                    throw new InvalidOperationException($"Rust could not extract '{path}': {error.Message}");
+                    throw new FileExtractionException(error.ParsedCode, $"Rust could not extract '{path}': {error.Message}", error.PageNumber, error.DetectedFormat);
                 }
 
                 if (processedEvent.PromptInjection is { } promptInjection)