Source code for hy.reader.hy_reader

"Character reader for parsing Hy source."

import hy
from hy.models import (
    Bytes,
    Complex,
    Dict,
    Expression,
    FComponent,
    Float,
    FString,
    Integer,
    Keyword,
    List,
    Set,
    String,
    Symbol,
    Tuple,
    as_model,
)

from .exceptions import LexException, PrematureEndOfInput
from .mangling import mangle
from .reader import Reader, isnormalizedspace


def sym(name):
    return Symbol(name, from_parser=True)


# Note: This is subtly different from
# the `mkexpr` in hy/compiler.py !
def mkexpr(root, *args):
    return Expression((sym(root) if isinstance(root, str) else root, *args))


def symbol_like(ident, reader=None):
    """Generate a Hy model from an identifier-like string.

    Also verifies the syntax of dot notation and validity of symbol names.

    Parameters
    ----------
    ident : str
        Text to convert.

    reader : Reader, optional
        The reader to use, if any; used for generating position data for errors.

    Returns
    -------
    out : a hy.models.Object subtype corresponding to the parsed text.
    """
    try:
        return Integer(ident)
    except ValueError:
        pass
    try:
        return Float(ident)
    except ValueError:
        pass
    if ident not in ("j", "J"):
        try:
            return Complex(ident)
        except ValueError:
            pass

    if "." in ident:
        for chunk in ident.split("."):
            if chunk and not isinstance(symbol_like(chunk, reader=reader), Symbol):
                msg = (
                    "Cannot access attribute on anything other"
                    " than a name (in order to get attributes of expressions,"
                    " use `(. <expression> <attr>)` or `(.<attr> <expression>)`)"
                )
                if reader is None:
                    raise ValueError(msg)
                else:
                    raise LexException.from_reader(msg, reader)

    if reader is None:
        if (
            not ident
            or ident[:1] == ":"
            or any(isnormalizedspace(c) for c in ident)
            or HyReader.NON_IDENT.intersection(ident)
        ):
            raise ValueError(f"Syntactically illegal symbol: {ident!r}")

    return sym(ident)


[docs]class HyReader(Reader): """A modular reader for Hy source.""" ### # Components necessary for Reader implementation ### NON_IDENT = set("()[]{};\"'")
[docs] def fill_pos(self, model, start): """Attach line/col information to a model. Sets the end location of `model` to the current cursor position. Args: model (hy.models.Object): model to set line/col info for. start (tuple[int, int]): (line, column) tuple indicating the start location to assign to `model`. """ model.start_line, model.start_column = start model.end_line, model.end_column = self.pos return model
[docs] def read_default(self, key): """Default reader handler when nothing in the table matches. Try to read an identifier/symbol. If there's a double-quote immediately following, then parse it as a string with the given prefix (e.g., `r"..."`). Otherwise, parse it as a symbol-like. """ ident = key + self.read_ident() if self.peek_and_getc('"'): return self.prefixed_string('"', ident) return symbol_like(ident, reader=self)
[docs] def parse(self, stream, filename=None): """Yields all `hy.models.Object`'s in `source` Additionally exposes `self` as ``hy.&reader`` during read/compile time. Args: source: Hy source to be parsed. filename (str | None): Filename to use for error messages. If `None` then previously set filename is used. """ self._set_source(stream, filename) rname = mangle("&reader") old_reader = getattr(hy, rname, None) setattr(hy, rname, self) try: yield from self.parse_forms_until("") finally: if old_reader is None: delattr(hy, rname) else: setattr(hy, rname, old_reader)
### # Reading forms ### def try_parse_one_form(self): """Attempt to parse a single Hy form. Read one (non-space) character from the stream, then call the corresponding handler. Returns: hy.models.Object | None: Model optionally returned by the called handler. Handlers may return `None` to signify no parsed form (e.g., for comments). Raises: PrematureEndOfInput: If the reader hits the end of the file before fully parsing a form. LexException: If there is an error during form parsing. """ try: self.slurp_space() c = self.getc() start = self._pos if not c: raise PrematureEndOfInput.from_reader( "Premature end of input while attempting to parse one form", self ) handler = self.reader_table.get(c) model = handler(self, c) if handler else self.read_default(c) return self.fill_pos(model, start) if model is not None else None except LexException: raise except Exception as e: raise LexException.from_reader( str(e) or "Exception thrown attempting to parse one form", self )
[docs] def parse_one_form(self): """Read from the stream until a form is parsed. Guaranteed to return a model (i.e., skips over comments). Returns: hy.models.Object """ model = None while model is None: model = self.try_parse_one_form() return model
[docs] def parse_forms_until(self, closer): """Yields `hy.models.Object`'s until character `closer` is seen. Useful for reading a sequence such as s-exprs or lists. """ while True: self.slurp_space() if self.peek_and_getc(closer): break model = self.try_parse_one_form() if model is not None: yield model
### # Basic atoms ### @reader_for(")") @reader_for("]") @reader_for("}") def INVALID(self, key): raise LexException.from_reader( f"Ran into a '{key}' where it wasn't expected.", self ) @reader_for(";") def line_comment(self, _): any(c == "\n" for c in self.chars(eof_ok=True)) return None @reader_for(":") def keyword(self, _): ident = self.read_ident() if "." in ident: raise LexException.from_reader( "Cannot access attribute on anything other" " than a name (in order to get attributes of expressions," " use `(. <expression> <attr>)` or `(.<attr> <expression>)`)", self, ) return Keyword(ident, from_parser=True) @reader_for('"') def prefixed_string(self, _, prefix=""): prefix_chars = set(prefix) if ( len(prefix_chars) != len(prefix) or prefix_chars - set("bfr") or set("bf") <= prefix_chars ): raise LexException.from_reader(f"invalid string prefix {prefix!r}", self) escaping = False def quote_closing(c): nonlocal escaping if c == "\\": escaping = not escaping return 0 if c == '"' and not escaping: return 1 if ( escaping and "r" not in prefix and # https://docs.python.org/3/reference/lexical_analysis.html#string-and-bytes-literals c not in ("\n\r\\'\"abfnrtv01234567x" + ("" if "b" in prefix else "NuU")) ): raise LexException.from_reader("invalid escape sequence \\" + c, self) escaping = False return 0 return self.read_string_until(quote_closing, prefix, "f" in prefix.lower()) ### # Special annotations ### @reader_for("'", ("quote",)) @reader_for("`", ("quasiquote",)) def tag_as(root): def _tag_as(self, _): nc = self.peekc() if ( not nc or isnormalizedspace(nc) or self.reader_table.get(nc) == self.INVALID ): raise LexException.from_reader( "Could not identify the next token.", self ) model = self.parse_one_form() return mkexpr(root, model) return _tag_as @reader_for("~") def unquote(self, key): nc = self.peekc() if not nc or isnormalizedspace(nc) or self.reader_table.get(nc) == self.INVALID: return sym(key) return mkexpr( "unquote" + ("-splice" if self.peek_and_getc("@") else ""), self.parse_one_form(), ) ### # Sequences ### @reader_for("(", (Expression, ")")) @reader_for("[", (List, "]")) @reader_for("{", (Dict, "}")) @reader_for("#{", (Set, "}")) @reader_for("#(", (Tuple, ")")) def sequence(seq_type, closer): return lambda self, _: seq_type(self.parse_forms_until(closer)) ### # Reader tag-macros ### @reader_for("#") def tag_dispatch(self, key): """General handler for reader macros (and tag macros). Reads a full identifier after the `#` and calls the corresponding handler (this allows, e.g., `#reads-multiple-forms foo bar baz`). Failing that, reads a single character after the `#` and immediately calls the corresponding handler (this allows, e.g., `#*args` to parse as `#*` followed by `args`). """ if not self.peekc(): raise PrematureEndOfInput.from_reader( "Premature end of input while attempting dispatch", self ) if self.peek_and_getc("^"): typ = self.parse_one_form() target = self.parse_one_form() return mkexpr("annotate", target, typ) tag = None # try dispatching tagged ident ident = self.read_ident(just_peeking=True) if ident and mangle(key + ident) in self.reader_table: self.getn(len(ident)) tag = mangle(key + ident) # failing that, dispatch tag + single character elif key + self.peekc() in self.reader_table: tag = key + self.getc() if tag: tree = self.dispatch(tag) return as_model(tree) if tree is not None else None raise LexException.from_reader( f"reader macro '{key + self.read_ident()}' is not defined", self ) @reader_for("#_") def discard(self, _): """Discards the next parsed form.""" self.parse_one_form() return None @reader_for("#*") def hash_star(self, _): """Unpacking forms `#*` and `#**`, corresponding to `*` and `**` in Python.""" num_stars = 1 while self.peek_and_getc("*"): num_stars += 1 if num_stars > 2: raise LexException.from_reader("too many stars", self) return mkexpr( "unpack-" + ("iterable", "mapping")[num_stars - 1], self.parse_one_form(), ) ### # Strings # (these are more complicated because f-strings # form their own sublanguage) ### @reader_for("#[") def bracketed_string(self, _): """Bracketed strings. See the Hy docs for full details.""" delim = [] for c in self.chars(): if c == "[": break elif c == "]": raise LexException.from_reader( "Ran into a ']' where it wasn't expected.", self ) delim.append(c) delim = "".join(delim) is_fstring = delim == "f" or delim.startswith("f-") # discard single initial newline, if any, accounting for all # three styles of newline self.peek_and_getc("\x0d") self.peek_and_getc("\x0a") index = -1 def delim_closing(c): nonlocal index if c == "]": if index == len(delim): # this is the second bracket at the end of the delim return len(delim) + 2 else: # reset state, this may be the first bracket of closing delim index = 0 elif 0 <= index <= len(delim): # we're inside a possible closing delim if index < len(delim) and c == delim[index]: index += 1 else: # failed delim, reset state index = -1 return 0 return self.read_string_until(delim_closing, None, is_fstring, brackets=delim) def read_string_until(self, closing, prefix, is_fstring, **kwargs): if is_fstring: components = self.read_fcomponents_until(closing, prefix) return FString(components, **kwargs) s = self.read_chars_until(closing, prefix, is_fstring=False) return (Bytes if isinstance(s, bytes) else String)(s, **kwargs) def read_chars_until(self, closing, prefix, is_fstring): s = [] for c in self.chars(): s.append(c) # check if c is closing n_closing_chars = closing(c) if n_closing_chars: # string has ended s = s[:-n_closing_chars] break # check if c is start of component if is_fstring and c == "{" and s[-3:] != ["\\", "N", "{"]: # check and handle "{{" if self.peek_and_getc("{"): s.append("{") else: # remove "{" from end of string component s.pop() break res = "".join(s).replace("\x0d\x0a", "\x0a").replace("\x0d", "\x0a") if prefix is not None: res = eval(f'{prefix}"""{res}"""') if is_fstring: return res, n_closing_chars return res def read_fcomponents_until(self, closing, prefix): components = [] start = self.pos while True: s, closed = self.read_chars_until(closing, prefix, is_fstring=True) if s: components.append(self.fill_pos(String(s), start)) if closed: break components.extend(self.read_fcomponent(prefix)) return components def read_fcomponent(self, prefix): """May return one or two components, since the `=` debugging syntax will create a String component.""" start = self.pos values = [] conversion = None has_debug = False # read the expression, saving the text verbatim # in case we encounter debug `=` space_before = self.slurp_space() with self.saving_chars() as form_text: model = self.parse_one_form() space_between = self.slurp_space() # check for and handle debug syntax: # we emt the verbatim text before we emit the value if self.peek_and_getc("="): has_debug = True space_after = self.slurp_space() dbg_prefix = ( space_before + "".join(form_text) + space_between + "=" + space_after ) values.append(self.fill_pos(String(dbg_prefix), start)) # handle conversion code if self.peek_and_getc("!"): conversion = self.getc() self.slurp_space() def component_closing(c): if c == "}": return 1 return 0 # handle formatting options format_components = [] if self.peek_and_getc(":"): format_components = self.read_fcomponents_until(component_closing, prefix) else: if has_debug and conversion is None: conversion = "r" if not self.getc() == "}": raise LexException.from_reader("f-string: trailing junk in field", self) return values + [ self.fill_pos(FComponent((model, *format_components), conversion), start) ]