--- a/DebugClients/Python/coverage/templite.py Sat Oct 10 12:06:10 2015 +0200
+++ b/DebugClients/Python/coverage/templite.py Sat Oct 10 12:44:52 2015 +0200
@@ -1,10 +1,28 @@
-"""A simple Python template renderer, for a nano-subset of Django syntax."""
+# Licensed under the Apache License: http://www.apache.org/licenses/LICENSE-2.0
+# For details: https://bitbucket.org/ned/coveragepy/src/default/NOTICE.txt
+
+"""A simple Python template renderer, for a nano-subset of Django syntax.
+
+For a detailed discussion of this code, see this chapter from 500 Lines:
+http://aosabook.org/en/500L/a-template-engine.html
+
+"""
# Coincidentally named the same as http://code.activestate.com/recipes/496702/
import re
-from .backward import set # pylint: disable=W0622
+from coverage import env
+
+
+class TempliteSyntaxError(ValueError):
+ """Raised when a template has a syntax error."""
+ pass
+
+
+class TempliteValueError(ValueError):
+ """Raised when an expression won't evaluate in a template."""
+ pass
class CodeBuilder(object):
@@ -12,42 +30,45 @@
def __init__(self, indent=0):
self.code = []
- self.indent_amount = indent
+ self.indent_level = indent
+
+ def __str__(self):
+ return "".join(str(c) for c in self.code)
def add_line(self, line):
"""Add a line of source to the code.
- Don't include indentations or newlines.
+ Indentation and newline will be added for you, don't provide them.
"""
- self.code.append(" " * self.indent_amount)
- self.code.append(line)
- self.code.append("\n")
+ self.code.extend([" " * self.indent_level, line, "\n"])
def add_section(self):
"""Add a section, a sub-CodeBuilder."""
- sect = CodeBuilder(self.indent_amount)
- self.code.append(sect)
- return sect
+ section = CodeBuilder(self.indent_level)
+ self.code.append(section)
+ return section
+
+ INDENT_STEP = 4 # PEP8 says so!
def indent(self):
"""Increase the current indent for following lines."""
- self.indent_amount += 4
+ self.indent_level += self.INDENT_STEP
def dedent(self):
"""Decrease the current indent for following lines."""
- self.indent_amount -= 4
-
- def __str__(self):
- return "".join([str(c) for c in self.code])
+ self.indent_level -= self.INDENT_STEP
- def get_function(self, fn_name):
- """Compile the code, and return the function `fn_name`."""
- assert self.indent_amount == 0
- g = {}
- code_text = str(self)
- exec(code_text, g)
- return g[fn_name]
+ def get_globals(self):
+ """Execute the code, and return a dict of globals it defines."""
+ # A check that the caller really finished all the blocks they started.
+ assert self.indent_level == 0
+ # Get the Python source as a single string.
+ python_source = str(self)
+ # Execute the source, defining globals, and return them.
+ global_namespace = {}
+ exec(python_source, global_namespace)
+ return global_namespace
class Templite(object):
@@ -55,7 +76,7 @@
Supported constructs are extended variable access::
- {{var.modifer.modifier|filter|filter}}
+ {{var.modifier.modifier|filter|filter}}
loops::
@@ -70,7 +91,20 @@
{# This will be ignored #}
Construct a Templite with the template text, then use `render` against a
- dictionary context to create a finished string.
+ dictionary context to create a finished string::
+
+ templite = Templite('''
+ <h1>Hello {{name|upper}}!</h1>
+ {% for topic in topics %}
+ <p>You are interested in {{topic}}.</p>
+ {% endif %}
+ ''',
+ {'upper': str.upper},
+ )
+ text = templite.render({
+ 'name': "Ned",
+ 'topics': ['Python', 'Geometry', 'Juggling'],
+ })
"""
def __init__(self, text, *contexts):
@@ -80,110 +114,139 @@
These are good for filters and global values.
"""
- self.text = text
self.context = {}
for context in contexts:
self.context.update(context)
+ self.all_vars = set()
+ self.loop_vars = set()
+
# We construct a function in source form, then compile it and hold onto
# it, and execute it to render the template.
code = CodeBuilder()
- code.add_line("def render(ctx, dot):")
+ code.add_line("def render_function(context, do_dots):")
code.indent()
vars_code = code.add_section()
- self.all_vars = set()
- self.loop_vars = set()
code.add_line("result = []")
- code.add_line("a = result.append")
- code.add_line("e = result.extend")
- code.add_line("s = str")
+ code.add_line("append_result = result.append")
+ code.add_line("extend_result = result.extend")
+ if env.PY2:
+ code.add_line("to_str = unicode")
+ else:
+ code.add_line("to_str = str")
buffered = []
+
def flush_output():
"""Force `buffered` to the code builder."""
if len(buffered) == 1:
- code.add_line("a(%s)" % buffered[0])
+ code.add_line("append_result(%s)" % buffered[0])
elif len(buffered) > 1:
- code.add_line("e([%s])" % ",".join(buffered))
+ code.add_line("extend_result([%s])" % ", ".join(buffered))
del buffered[:]
- # Split the text to form a list of tokens.
- toks = re.split(r"(?s)({{.*?}}|{%.*?%}|{#.*?#})", text)
-
ops_stack = []
- for tok in toks:
- if tok.startswith('{{'):
- # An expression to evaluate.
- buffered.append("s(%s)" % self.expr_code(tok[2:-2].strip()))
- elif tok.startswith('{#'):
+
+ # Split the text to form a list of tokens.
+ tokens = re.split(r"(?s)({{.*?}}|{%.*?%}|{#.*?#})", text)
+
+ for token in tokens:
+ if token.startswith('{#'):
# Comment: ignore it and move on.
continue
- elif tok.startswith('{%'):
+ elif token.startswith('{{'):
+ # An expression to evaluate.
+ expr = self._expr_code(token[2:-2].strip())
+ buffered.append("to_str(%s)" % expr)
+ elif token.startswith('{%'):
# Action tag: split into words and parse further.
flush_output()
- words = tok[2:-2].strip().split()
+ words = token[2:-2].strip().split()
if words[0] == 'if':
# An if statement: evaluate the expression to determine if.
- assert len(words) == 2
+ if len(words) != 2:
+ self._syntax_error("Don't understand if", token)
ops_stack.append('if')
- code.add_line("if %s:" % self.expr_code(words[1]))
+ code.add_line("if %s:" % self._expr_code(words[1]))
code.indent()
elif words[0] == 'for':
# A loop: iterate over expression result.
- assert len(words) == 4 and words[2] == 'in'
+ if len(words) != 4 or words[2] != 'in':
+ self._syntax_error("Don't understand for", token)
ops_stack.append('for')
- self.loop_vars.add(words[1])
+ self._variable(words[1], self.loop_vars)
code.add_line(
"for c_%s in %s:" % (
words[1],
- self.expr_code(words[3])
+ self._expr_code(words[3])
)
)
code.indent()
elif words[0].startswith('end'):
- # Endsomething. Pop the ops stack
+ # Endsomething. Pop the ops stack.
+ if len(words) != 1:
+ self._syntax_error("Don't understand end", token)
end_what = words[0][3:]
- if ops_stack[-1] != end_what:
- raise SyntaxError("Mismatched end tag: %r" % end_what)
- ops_stack.pop()
+ if not ops_stack:
+ self._syntax_error("Too many ends", token)
+ start_what = ops_stack.pop()
+ if start_what != end_what:
+ self._syntax_error("Mismatched end tag", end_what)
code.dedent()
else:
- raise SyntaxError("Don't understand tag: %r" % words[0])
+ self._syntax_error("Don't understand tag", words[0])
else:
# Literal content. If it isn't empty, output it.
- if tok:
- buffered.append("%r" % tok)
+ if token:
+ buffered.append(repr(token))
+
+ if ops_stack:
+ self._syntax_error("Unmatched action tag", ops_stack[-1])
+
flush_output()
for var_name in self.all_vars - self.loop_vars:
- vars_code.add_line("c_%s = ctx[%r]" % (var_name, var_name))
-
- if ops_stack:
- raise SyntaxError("Unmatched action tag: %r" % ops_stack[-1])
+ vars_code.add_line("c_%s = context[%r]" % (var_name, var_name))
- code.add_line("return ''.join(result)")
+ code.add_line('return "".join(result)')
code.dedent()
- self.render_function = code.get_function('render')
+ self._render_function = code.get_globals()['render_function']
- def expr_code(self, expr):
+ def _expr_code(self, expr):
"""Generate a Python expression for `expr`."""
if "|" in expr:
pipes = expr.split("|")
- code = self.expr_code(pipes[0])
+ code = self._expr_code(pipes[0])
for func in pipes[1:]:
- self.all_vars.add(func)
+ self._variable(func, self.all_vars)
code = "c_%s(%s)" % (func, code)
elif "." in expr:
dots = expr.split(".")
- code = self.expr_code(dots[0])
- args = [repr(d) for d in dots[1:]]
- code = "dot(%s, %s)" % (code, ", ".join(args))
+ code = self._expr_code(dots[0])
+ args = ", ".join(repr(d) for d in dots[1:])
+ code = "do_dots(%s, %s)" % (code, args)
else:
- self.all_vars.add(expr)
+ self._variable(expr, self.all_vars)
code = "c_%s" % expr
return code
+ def _syntax_error(self, msg, thing):
+ """Raise a syntax error using `msg`, and showing `thing`."""
+ raise TempliteSyntaxError("%s: %r" % (msg, thing))
+
+ def _variable(self, name, vars_set):
+ """Track that `name` is used as a variable.
+
+ Adds the name to `vars_set`, a set of variable names.
+
+ Raises an syntax error if `name` is not a valid name.
+
+ """
+ if not re.match(r"[_a-zA-Z][_a-zA-Z0-9]*$", name):
+ self._syntax_error("Not a valid name", name)
+ vars_set.add(name)
+
def render(self, context=None):
"""Render this template by applying it to `context`.
@@ -191,19 +254,24 @@
"""
# Make the complete context we'll use.
- ctx = dict(self.context)
+ render_context = dict(self.context)
if context:
- ctx.update(context)
- return self.render_function(ctx, self.do_dots)
+ render_context.update(context)
+ return self._render_function(render_context, self._do_dots)
- def do_dots(self, value, *dots):
- """Evaluate dotted expressions at runtime."""
+ def _do_dots(self, value, *dots):
+ """Evaluate dotted expressions at run-time."""
for dot in dots:
try:
value = getattr(value, dot)
except AttributeError:
- value = value[dot]
- if hasattr(value, '__call__'):
+ try:
+ value = value[dot]
+ except (TypeError, KeyError):
+ raise TempliteValueError(
+ "Couldn't evaluate %r.%s" % (value, dot)
+ )
+ if callable(value):
value = value()
return value
