Templite now compiles to Python code for speed.

1 files changed, 102 insertions, 92 deletions

diff --git a/coverage/templite.py b/coverage/templite.py
index c39e061e..2ca12fef 100644
--- a/coverage/templite.py
+++ b/coverage/templite.py
@@ -2,7 +2,42 @@
 
 # Coincidentally named the same as http://code.activestate.com/recipes/496702/
 
-import re, sys
+import re
+
+
+class CodeBuilder(object):
+    """Build source code conveniently."""
+
+    def __init__(self):
+        self.code = []
+        self.indent_amount = 0
+
+    def add_line(self, line):
+        """Add a line of source to the code.
+
+        Don't include indentations or newlines.
+
+        """
+        self.code.append(" " * self.indent_amount)
+        self.code.append(line)
+        self.code.append("\n")
+
+    def indent(self):
+        """Increase the current indent for following lines."""
+        self.indent_amount += 4
+
+    def dedent(self):
+        """Decrease the current indent for following lines."""
+        self.indent_amount -= 4
+
+    def get_function(self, fn_name):
+        """Compile the code, and return the function `fn_name`."""
+        assert self.indent_amount == 0
+        g = {}
+        code_text = "".join(self.code)
+        exec(code_text, g)
+        return g[fn_name]
+
 
 class Templite(object):
     """A simple template renderer, for a nano-subset of Django syntax.
@@ -39,22 +74,23 @@ class Templite(object):
         for context in contexts:
             self.context.update(context)
 
+        # We construct a function in source form, then compile it and hold onto
+        # it, and execute it to create the template output.
+        code = CodeBuilder()
+
+        code.add_line("def render(ctx, dot):")
+        code.indent()
+        code.add_line("result = []")
+        code.add_line("r = result.append")
+
         # Split the text to form a list of tokens.
         toks = re.split(r"(?s)({{.*?}}|{%.*?%}|{#.*?#})", text)
 
-        # Parse the tokens into a nested list of operations.  Each item in the
-        # list is a tuple with an opcode, and arguments.  They'll be
-        # interpreted by TempliteEngine.
-        #
-        # When parsing an action tag with nested content (if, for), the current
-        # ops list is pushed onto ops_stack, and the parsing continues in a new
-        # ops list that is part of the arguments to the if or for op.
-        ops = []
         ops_stack = []
         for tok in toks:
             if tok.startswith('{{'):
-                # Expression: ('exp', expr)
-                ops.append(('exp', tok[2:-2].strip()))
+                # An expression to evaluate.
+                code.add_line("r(str(%s))" % self.expr_code(tok[2:-2].strip()))
             elif tok.startswith('{#'):
                 # Comment: ignore it and move on.
                 continue
@@ -62,30 +98,58 @@ class Templite(object):
                 # Action tag: split into words and parse further.
                 words = tok[2:-2].strip().split()
                 if words[0] == 'if':
-                    # If: ('if', (expr, body_ops))
-                    if_ops = []
+                    # An if statement: evaluate the expression to determine if.
                     assert len(words) == 2
-                    ops.append(('if', (words[1], if_ops)))
-                    ops_stack.append(ops)
-                    ops = if_ops
+                    ops_stack.append('if')
+                    code.add_line("if %s:" % self.expr_code(words[1]))
+                    code.indent()
                 elif words[0] == 'for':
-                    # For: ('for', (varname, listexpr, body_ops))
+                    # A loop: iterate over expression result.
                     assert len(words) == 4 and words[2] == 'in'
-                    for_ops = []
-                    ops.append(('for', (words[1], words[3], for_ops)))
-                    ops_stack.append(ops)
-                    ops = for_ops
+                    ops_stack.append('for')
+                    code.add_line(
+                        "for ctx[%r] in %s:" % (
+                            words[1],
+                            self.expr_code(words[3])
+                        )
+                    )
+                    code.indent()
                 elif words[0].startswith('end'):
                     # Endsomething.  Pop the ops stack
-                    ops = ops_stack.pop()
-                    assert ops[-1][0] == words[0][3:]
+                    end_what = words[0][3:]
+                    if ops_stack[-1] != end_what:
+                        raise SyntaxError("Mismatched end tag: %r" % end_what)
+                    ops_stack.pop()
+                    code.dedent()
                 else:
-                    raise SyntaxError("Don't understand tag %r" % words)
+                    raise SyntaxError("Don't understand tag: %r" % words[0])
             else:
-                ops.append(('lit', tok))
+                # Literal content.  If it isn't empty, output it.
+                if tok:
+                    code.add_line("r(%r)" % tok)
+
+        if ops_stack:
+            raise SyntaxError("Unmatched action tag: %r" % ops_stack[-1])
 
-        assert not ops_stack, "Unmatched action tag: %r" % ops_stack[-1][0]
-        self.ops = ops
+        code.add_line("return ''.join(result)")
+        code.dedent()
+        self.render_function = code.get_function('render')
+
+    def expr_code(self, expr):
+        """Generate a Python expression for `expr`."""
+        if "|" in expr:
+            pipes = expr.split("|")
+            code = self.expr_code(pipes[0])
+            for func in pipes[1:]:
+                code = "ctx[%r](%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))
+        else:
+            code = "ctx[%r]" % expr
+        return code
 
     def render(self, context=None):
         """Render this template by applying it to `context`.
@@ -98,69 +162,15 @@ class Templite(object):
         if context:
             ctx.update(context)
 
-        # Run it through an engine, and return the result.
-        engine = _TempliteEngine(ctx)
-        engine.execute(self.ops)
-        return "".join(engine.result)
-
-
-class _TempliteEngine(object):
-    """Executes Templite objects to produce strings."""
-    def __init__(self, context):
-        self.context = context
-        self.result = []
-
-    def execute(self, ops):
-        """Execute `ops` in the engine.
-
-        Called recursively for the bodies of if's and loops.
-
-        """
-        for op, args in ops:
-            if op == 'lit':
-                self.result.append(args)
-            elif op == 'exp':
-                try:
-                    self.result.append(str(self.evaluate(args)))
-                except:
-                    exc_class, exc, _ = sys.exc_info()
-                    new_exc = exc_class("Couldn't evaluate {{ %s }}: %s"
-                                        % (args, exc))
-                    raise new_exc
-            elif op == 'if':
-                expr, body = args
-                if self.evaluate(expr):
-                    self.execute(body)
-            elif op == 'for':
-                var, lis, body = args
-                vals = self.evaluate(lis)
-                for val in vals:
-                    self.context[var] = val
-                    self.execute(body)
-            else:
-                raise AssertionError("TempliteEngine doesn't grok op %r" % op)
-
-    def evaluate(self, expr):
-        """Evaluate an expression.
-
-        `expr` can have pipes and dots to indicate data access and filtering.
-
-        """
-        if "|" in expr:
-            pipes = expr.split("|")
-            value = self.evaluate(pipes[0])
-            for func in pipes[1:]:
-                value = self.evaluate(func)(value)
-        elif "." in expr:
-            dots = expr.split('.')
-            value = self.evaluate(dots[0])
-            for dot in dots[1:]:
-                try:
-                    value = getattr(value, dot)
-                except AttributeError:
-                    value = value[dot]
-                if hasattr(value, '__call__'):
-                    value = value()
-        else:
-            value = self.context[expr]
+        return self.render_function(ctx, self.do_dots)
+
+    def do_dots(self, value, *dots):
+        """Evaluate dotted expressions at runtime."""
+        for dot in dots:
+            try:
+                value = getattr(value, dot)
+            except AttributeError:
+                value = value[dot]
+            if hasattr(value, '__call__'):
+                value = value()
         return value