Portable Text fields throw "Attempt to apply insert patch to non-array value" when pasting content

[wiiiimm]

Describe the bug

When using Portable Text fields (block content) with sanity-plugin-internationalized-array, pasting content into an empty field throws an error:

Error: Attempt to apply insert patch to non-array value

This happens specifically when:

1. The field is wrapped with internationalizedArray
2. The field type is a Portable Text array field (e.g., body, htmlContent)
3. The field is empty and you try to paste content into it

Root Cause

The plugin doesn't properly initialize the nested value field as an empty array for Portable Text fields. When Sanity's Portable Text editor tries to apply an InsertPatch operation to paste content, it expects an array but finds undefined or a non-array value.

To Reproduce

1. Create a schema with an internationalized Portable Text field:

defineField({
  name: 'body',
  title: 'Body',
  type: 'internationalizedArrayBody',
  group: 'editorial',
})

2. Open a document with this field in Sanity Studio
3. Try to paste any content into the empty Portable Text editor
4. See error: "Attempt to apply insert patch to non-array value"

Expected behavior

The Portable Text field should accept pasted content without errors, just like non-internationalized Portable Text fields do.

Workaround Attempts

Tried several workarounds without success:

• Adding initialValue to set empty arrays
• Creating wrapper components to intercept and fix patches
• Attempting to monkey-patch InsertPatch.apply

Which versions of Sanity are you using?

• sanity: 3.62.3
• sanity-plugin-internationalized-array: 3.1.5

What operating system are you using?

macOS

Which versions of Node.js / npm are you running?

• Node: v20.11.1
• pnpm: 9.12.3

Additional context

This is a critical issue for content editors who rely on copy-paste workflows. The issue occurs specifically with array-based field types (Portable Text) when they're wrapped by the internationalized array plugin.

The fix likely needs to ensure that when a language tab is selected, the value field for array-based content types is properly initialized as an empty array [] rather than undefined.

[wiiiimm]

Update: Root Cause Identified and Fixed

After further investigation, I discovered the issue is specifically with document-level "Add translation" buttons when the buttonLocations config includes 'document'.

The Actual Problem

The bug only occurs when:

1. Using the document-level "Add translation to internationalized fields" button
2. Adding a locale to Portable Text fields (or other array-based fields)
3. The field is empty/uninitialized

The field-level buttons and unstable_fieldAction buttons work correctly and don't have this issue.

Root Cause

In src/components/DocumentAddButtons.tsx, when creating patches for new language entries, all fields were initialized with value: undefined. This causes Sanity's Portable Text editor to fail when trying to apply insert patches (like when pasting content), as it expects an array.

The Solution

Modified DocumentAddButtons.tsx to:

1. Detect array-based field types using schema inspection via useSchema hook
2. Initialize array fields with [] instead of undefined
3. Also added a fix in InternationalizedInput.tsx to handle paste operations into empty fields

The fix intelligently detects array fields by:

• Checking if the field's jsonType is 'array'
• Matching against known Portable Text field names
• Examining the schema type definition

Testing

Confirmed the fix works with:

• Document-level locale addition for Portable Text fields
• Pasting content into newly created empty fields
• Field-level and unstable_fieldAction buttons (which already worked)

PR #105 has been updated with the correct fix.