YAML Validation Errors

These errors appear when validating or parsing YAML configuration files, particularly in the Converter and Developer Mode.

Error Patterns

Bad Indentation

Message: “The file has a formatting error: indentation (spaces at the beginning of the line) is incorrect.”

Cause: YAML uses spaces for indentation, and they must be consistent.

Bad example:

items:
  my_item:
      display_name: "Sword"
    material: PAPER    # Wrong! Inconsistent indentation

Fixed:

items:
  my_item:
    display_name: "Sword"
    material: PAPER

Rule: Use 2 spaces per indentation level. Never mix tabs and spaces.

Unexpected End of File

Message: “The file is incomplete. Verify that all sections are properly closed.”

Cause: The YAML file is cut off or missing closing elements.

Bad example:

items:
  my_item:
    display_name: "Sword"
    material:

Fixed:

items:
  my_item:
    display_name: "Sword"
    material: PAPER

Duplicate Key

Message: “The file has duplicate keys. Each property name must be unique in its section.”

Cause: The same key appears twice at the same level.

Bad example:

items:
  my_item:
    display_name: "Sword"
    material: PAPER
    display_name: "Better Sword"  # Duplicate!

Fixed:

items:
  my_item:
    display_name: "Better Sword"
    material: PAPER

Unexpected Token

Message: “The file has an unexpected character. Check the file syntax.”

Cause: A character appeared where YAML didn’t expect it.

Common causes:

• Unquoted strings starting with special characters ({, [, *, &, !, %, @)
• Missing colon after a key
• Missing space after the colon

Bad example:

items:
  my_item:
    display_name:Sword  # Missing space after colon

Fixed:

items:
  my_item:
    display_name: Sword

Invalid Tag

Message: “The file contains an invalid YAML tag.”

Cause: An unrecognized YAML tag was used (e.g., !!python/object).

Solution: Remove any YAML tags that start with ! unless they are specifically required by your plugin.

Mapping Values Not Allowed

Message: “The file has a structure error. Verify that values are correctly assigned with ’:’.”

Cause: A value was placed where a mapping key was expected.

Bad example:

items:
  my_item:
    display_name: "My Item"
  material: PAPER  # Wrong level — should be inside my_item

Fixed:

items:
  my_item:
    display_name: "My Item"
    material: PAPER

Incomplete Key-Value Pair

Message: “The file has an incomplete property. Make sure each key has an assigned value.”

Cause: A key exists without a value, and YAML can’t infer what it should be.

Bad example:

items:
  my_item:
    display_name:
    material: PAPER

Fixed:

items:
  my_item:
    display_name: "My Item"
    material: PAPER

Tab Character

Message: “The file uses tabs instead of spaces. YAML only allows spaces for indentation.”

Cause: Tab characters (\t) were used for indentation.

Solution:

1. Configure your text editor to use spaces instead of tabs
2. In VS Code: Settings > Editor: Insert Spaces = true, Tab Size = 2
3. Use “Convert Indentation to Spaces” command in your editor

Empty File

Message: “The file is empty. Upload a YAML file with valid content.”

Solution: Make sure the file you’re uploading actually contains YAML content and isn’t a 0-byte file.

Tips for Writing Valid YAML

1. Always use spaces (2 per level), never tabs
2. Quote strings that contain special characters: display_name: "Item: Special"
3. Validate before uploading using the Developer Mode editor, which provides real-time feedback
4. Use a YAML-aware editor like VS Code with the YAML extension