Importing a JSON file that isn't a valid description array crashes Import with an unhandled JsonException

[matt-edmondson]

What's wrong

Import.ImportJson (ImageDescriber/Verbs/Import.cs:144-148) calls JsonSerializer.Deserialize<List<ImageDescription>> and catches no exceptions. Neither of its callers does either: LoadEntries (Import.cs:74-86) and Run (Import.cs:47-72).

As a result, any JSON file that fails to deserialize ends the process with a stack trace. That includes a truncated file, an object at the root instead of an array, a string where a number is expected, and a date that won't parse.

The CSV path already handles malformed input. ParseCsv catches FormatException, OverflowException and ArgumentException for each row, prints Skipping line N: ... and carries on (Import.cs:200-211).

Reproduction (verified on .NET 10, Linux)

echo '{"not":"array"}' > bad.json
ImageDescriber Import -i bad.json
Unhandled exception. System.Text.Json.JsonException: The JSON value could not be converted to
System.Collections.Generic.List`1[ktsu.ImageDescriber.ImageDescription]. Path: $ | LineNumber: 0 | BytePositionInLine: 1.

A file cut off mid-write, or a hand-edited file with a trailing comma, fails the same way. When Import is started from the interactive menu (the default verb), the crash also ends the menu session.

Why it matters

Import is how users move a database to another machine or restore an export. A bad file should produce a one-line error and leave the store untouched.

#171 mentions in passing that ImportJson doesn't catch the FileName validation exception. This issue is the general malformed-input case, which fixing #171 would not cover.

Suggested fix

• In ImportJson, catch JsonException from the deserialize call, plus ArgumentException for semantic-type validation. On failure, print Error: <file> is not a valid ImageDescriber JSON export: <message> and return null so that Run exits before Program.Settings.Save().
• Once ImageDescriber exits 0 on every failure (Ollama unreachable, missing import file, missing required option, failed images) #167 lands, return a non-zero exit code on this path as well.

Acceptance criteria

• Importing {"not":"array"}, a truncated JSON array, or an entry with "FileSizeBytes":"abc" prints an error naming the file and does not throw.
• persistent_state.json is unchanged afterwards.
• A test in ImageDescriber.Test/ImportTests.cs covers the error path.

[matt-edmondson]

Triage

• Category: Bug
• Priority: Low. A malformed JSON import crashes the process with a stack trace and ends the interactive session. The crash happens before Settings.Save(), so the store isn't damaged, and the fix is small.
• Area / suggested assignment: Import verb (Verbs/Import.cs ImportJson). @matt-edmondson
• Duplicates: None. Suggested file names made on Linux/macOS keep characters Windows rejects (: ? * < > | \ "), so they can't be used on Windows and a JSON import there aborts #171 touches the same method (the FileName validation exception), and the two could be fixed together. ImageDescriber exits 0 on every failure (Ollama unreachable, missing import file, missing required option, failed images) #167 (exit codes) is a follow-up.
• In progress: No open ImageDescriber PR.

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