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"""
Source code generator.
The `srcgen` module contains generic helper routines and classes for generating
source code.
"""
from __future__ import absolute_import
import sys
import os
from collections import OrderedDict
try:
from typing import Any, List, Set, Tuple # noqa
except ImportError:
pass
class Formatter(object):
"""
Source code formatter class.
- Collect source code to be written to a file.
- Keep track of indentation.
Indentation example:
>>> f = Formatter()
>>> f.line('Hello line 1')
>>> f.writelines()
Hello line 1
>>> f.indent_push()
>>> f.comment('Nested comment')
>>> f.indent_pop()
>>> f.format('Back {} again', 'home')
>>> f.writelines()
Hello line 1
// Nested comment
Back home again
"""
shiftwidth = 4
def __init__(self):
# type: () -> None
self.indent = ''
self.lines = [] # type: List[str]
def indent_push(self):
# type: () -> None
"""Increase current indentation level by one."""
self.indent += ' ' * self.shiftwidth
def indent_pop(self):
# type: () -> None
"""Decrease indentation by one level."""
assert self.indent != '', 'Already at top level indentation'
self.indent = self.indent[0:-self.shiftwidth]
def line(self, s=None):
# type: (str) -> None
"""Add an indented line."""
if s:
self.lines.append('{}{}\n'.format(self.indent, s))
else:
self.lines.append('\n')
def outdented_line(self, s):
# type: (str) -> None
"""
Emit a line outdented one level.
This is used for '} else {' and similar things inside a single indented
block.
"""
self.lines.append('{}{}\n'.format(self.indent[0:-self.shiftwidth], s))
def writelines(self, f=None):
# type: (Any) -> None
"""Write all lines to `f`."""
if not f:
f = sys.stdout
f.writelines(self.lines)
def update_file(self, filename, directory):
# type: (str, str) -> None
if directory is not None:
filename = os.path.join(directory, filename)
with open(filename, 'w') as f:
self.writelines(f)
class _IndentedScope(object):
def __init__(self, fmt, after):
# type: (Formatter, str) -> None
self.fmt = fmt
self.after = after
def __enter__(self):
# type: () -> None
self.fmt.indent_push()
def __exit__(self, t, v, tb):
# type: (object, object, object) -> None
self.fmt.indent_pop()
if self.after:
self.fmt.line(self.after)
def indented(self, before=None, after=None):
# type: (str, str) -> Formatter._IndentedScope
"""
Return a scope object for use with a `with` statement:
>>> f = Formatter()
>>> with f.indented('prefix {', '} suffix'):
... f.line('hello')
>>> f.writelines()
prefix {
hello
} suffix
The optional `before` and `after` parameters are surrounding lines
which are *not* indented.
"""
if before:
self.line(before)
return Formatter._IndentedScope(self, after)
def format(self, fmt, *args):
# type: (str, *Any) -> None
self.line(fmt.format(*args))
def multi_line(self, s):
# type: (str) -> None
"""Add one or more lines after stripping common indentation."""
for l in parse_multiline(s):
self.line(l)
def comment(self, s):
# type: (str) -> None
"""Add a comment line."""
self.line('// ' + s)
def doc_comment(self, s):
# type: (str) -> None
"""Add a (multi-line) documentation comment."""
for l in parse_multiline(s):
self.line('/// ' + l if l else '///')
def match(self, m):
# type: (Match) -> None
"""
Add a match expression.
Example:
>>> f = Formatter()
>>> m = Match('x')
>>> m.arm('Orange', ['a', 'b'], 'some body')
>>> m.arm('Yellow', ['a', 'b'], 'some body')
>>> m.arm('Green', ['a', 'b'], 'different body')
>>> m.arm('Blue', ['x', 'y'], 'some body')
>>> f.match(m)
>>> f.writelines()
match x {
Orange { a, b } |
Yellow { a, b } => {
some body
}
Green { a, b } => {
different body
}
Blue { x, y } => {
some body
}
}
"""
with self.indented('match {} {{'.format(m.expr), '}'):
for (fields, body), names in m.arms.items():
with self.indented('', '}'):
names_left = len(names)
for name in names.keys():
fields_str = ', '.join(fields)
if len(fields) != 0:
fields_str = '{{ {} }} '.format(fields_str)
names_left -= 1
if names_left > 0:
suffix = '|'
else:
suffix = '=> {'
self.outdented_line(name + ' ' + fields_str + suffix)
if names_left == 0:
self.multi_line(body)
def _indent(s):
# type: (str) -> int
"""
Compute the indentation of s, or None of an empty line.
Example:
>>> _indent("foo")
0
>>> _indent(" bar")
4
>>> _indent(" ")
>>> _indent("")
"""
t = s.lstrip()
return len(s) - len(t) if t else None
def parse_multiline(s):
# type: (str) -> List[str]
"""
Given a multi-line string, split it into a sequence of lines after
stripping a common indentation, as described in the "trim" function
from PEP 257. This is useful for strings defined with doc strings:
>>> parse_multiline('\\n hello\\n world\\n')
['hello', 'world']
"""
if not s:
return []
# Convert tabs to spaces (following the normal Python rules)
# and split into a list of lines:
lines = s.expandtabs().splitlines()
# Determine minimum indentation (first line doesn't count):
indent = sys.maxsize
for line in lines[1:]:
stripped = line.lstrip()
if stripped:
indent = min(indent, len(line) - len(stripped))
# Remove indentation (first line is special):
trimmed = [lines[0].strip()]
if indent < sys.maxsize:
for line in lines[1:]:
trimmed.append(line[indent:].rstrip())
# Strip off trailing and leading blank lines:
while trimmed and not trimmed[-1]:
trimmed.pop()
while trimmed and not trimmed[0]:
trimmed.pop(0)
return trimmed
class Match(object):
"""
Match formatting class.
Match objects collect all the information needed to emit a Rust `match`
expression, automatically deduplicating overlapping identical arms.
Example:
>>> m = Match('x')
>>> m.arm('Orange', ['a', 'b'], 'some body')
>>> m.arm('Yellow', ['a', 'b'], 'some body')
>>> m.arm('Green', ['a', 'b'], 'different body')
>>> m.arm('Blue', ['x', 'y'], 'some body')
>>> assert(len(m.arms) == 3)
Note that this class is ignorant of Rust types, and considers two fields
with the same name to be equivalent.
"""
def __init__(self, expr):
# type: (str) -> None
self.expr = expr
self.arms = OrderedDict() # type: OrderedDict[Tuple[Tuple[str, ...], str], OrderedDict[str, None]] # noqa
def arm(self, name, fields, body):
# type: (str, List[str], str) -> None
key = (tuple(fields), body)
if key not in self.arms:
self.arms[key] = OrderedDict()
self.arms[key][name] = None
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