Module refinery.lib.scripts.guess

Functions

def guess_language(data)

Try to parse the input as JavaScript, PowerShell, and VBA, then return the name of the language whose parser produces the fewest error nodes. Returns None when no parser can handle more than half of the input.

The count only separates the languages once the input is long enough for them to disagree about it. All three grammars read a script of a few lines without a single error — a Sub/End Sub block, a var declaration and a Write-Host call are each accepted by all three — so for a short input nothing but the order of backends decides, and PowerShell, the language this tool exists for, is asked first.

Expand source code Browse git

def guess_language(data: str | bytearray | bytes | memoryview) -> str | None:
    """
    Try to parse the input as JavaScript, PowerShell, and VBA, then return the name of the language
    whose parser produces the fewest error nodes. Returns `None` when no parser can handle more than
    half of the input.

    The count only separates the languages once the input is long enough for them to disagree about
    it. All three grammars read a script of a few lines without a single error — a `Sub`/`End Sub`
    block, a `var` declaration and a `Write-Host` call are each accepted by all three — so for a
    short input nothing but the order of `backends` decides, and PowerShell, the language this tool
    exists for, is asked first.
    """
    best_name: str | None = None
    best_errors = INF()

    from refinery.lib.scripts.js.model import JsErrorNode
    from refinery.lib.scripts.js.parser import JsParser
    from refinery.lib.scripts.ps1.model import Ps1ErrorNode
    from refinery.lib.scripts.ps1.parser import Ps1Parser
    from refinery.lib.scripts.vba.model import VbaErrorNode
    from refinery.lib.scripts.vba.parser import VbaParser

    backends = (
        ('ps1', Ps1Parser, Ps1ErrorNode),
        ('vba', VbaParser, VbaErrorNode),
        ('js', JsParser, JsErrorNode),
    )

    if not isinstance(data, str):
        import codecs
        data = codecs.decode(data, 'utf8', 'surrogateescape')

    for name, parser_type, error_type in backends:
        try:
            ast = parser_type(data).parse()
            errors = sum(
                len(n.text) for n in ast.walk() if isinstance(n, error_type))
        except Exception:
            continue
        if errors < best_errors:
            best_errors = errors
            best_name = name
            if errors == 0:
                break

    if best_name is None or best_errors * 2 > len(data):
        return None

    return best_name