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Breaking Changes.md

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Breaking Changes

wizparse is not 100% compatible with the original parser / interpreter.

I took this opportunity to fix some gigantic missteps in the original language. For example, this was valid syntax:

If a = 1
    Note 'foo'
EndIf

How would you guess this executed? The answer is that it would always execute the Note 'foo' statement, since a = 1 is an assignment, not a comparison, and returned the new value. The author probably meant to write this:

If a == 1
    Note 'foo'
EndIf

An actual example of a wizard that fell prey to this was the 1.97 version of SMIM for Skyrim LE:

If bHalfTex = 1
    SelectSubPackage "81 Half-Sized Furniture Skyrim HD Appearance"
EndIf

This would always select the half-sized textures, whether the user checked the option or not.

A full list of breaking changes follows:

  • Blocks must be closed properly now. Previously, they did not have to be, since the parser read files one line at a time. Consider this SelectOne statement:

    SelectOne 'Are you happy with your selection?',\
          'Finish', 'Finish executing the wizard', '',\
          'Abort', 'Discard all changes and abort', ''
    Case 'Option 1'
        Return
    Case 'Option 2'
        Cancel 'User aborted'

    It's clearly missing an EndSelect. However, because both Cancel and Return tell the interpreter to finish executing the wizard, it never actually reads the next line to notice the lack of an EndSelect. This is a necessary breaking change, since we now parse the entire file before interpreting.

  • The pseudo-bareword strings that the old parser accidentally accepted are now outlawed. This was valid:

    Note thisIsAString
; Prints 'thisIsAString'
thisIsAString = thisIsNotAString
Note thisIsAString
; Prints 'thisIsNotAString'

    They were never mentioned in documentation and I could not find a single wizard that used this (thank god). Still, this technically breaks backwards compatibility, so noting it here.

  • As mentioned above, assignments and compound assignments no longer return a value, meaning that they cannot be used for commands that expect a value (e.g. If statements).

  • SelectOne / SelectMany statements may now only contain a single Default statement at the end of the case list. Previously, any number were allowed and they could occur anywhere in the case list. Only a single one would have been executed, and the fallthrough logic made using them in any position except the last one awkward.

  • Functions now must have parentheses after them. Previously, this was allowed:

    Note 'foo'.len
; Prints '3'

    Now, functions must always be followed by parentheses, even if the argument list is empty. The documentation already made this clear, but the parser did not obey it.

  • Escape sequences are only allowed in strings now. Previously, this was legal:

    \; This is a comment
\Note \'\f\o\o'

    Now, only these escapes are legal:

    ; This is a comment
Note '\f\o\o'

    Note, however, that we still support arbitrary escape sequences in strings. This means you can escape any character in a string, even completely unnecessary ones, as the example above demonstrates. The reason is backwards compatibility: many wizards escape way too much, so removing it would cause breakage.

    There is an exception to this. Extraneous backslashes and whitespace at the end of a line are ignored:

    ; This is legal
Note 'foo' \\\\\\\

    The reason is, again, backwards compatibility. Double and triple backslashes for line continuation occur in several wizards and are relatively easy to support.

  • Random unicode characters in a wizard are no longer silently ignored, but instead cause an error. For example, one SSE wizard had several ▒ characters (MEDIUM SHADE, U+2592) at the end of a line.

Historical

These were previously listed as breaking changes, but have since made their way into the old parser as well.

  • New keywords:

    • DeSelectAllPlugins
    • DeSelectPlugin
    • RenamePlugin
    • ResetPluginName
    • SelectAllPlugins
    • SelectPlugin

    The old versions, with Espm instead of Plugin and Espms instead of Plugins, are deprecated but retained for backwards compatibility.

  • New operator: modulo (a % b) - calculates the remainder.