Add lookup expressions

blueprintcompiler/ast_utils.py

@@ -33,7 +33,10 @@ class Children:
     def __iter__(self):
         return iter(self._children)
     def __getitem__(self, key):
-        return [child for child in self._children if isinstance(child, key)]
+        if isinstance(key, int):
+            return self._children[key]
+        else:
+            return [child for child in self._children if isinstance(child, key)]
 
 
 class AstNode:

blueprintcompiler/language/__init__.py

@@ -2,6 +2,7 @@
 templates. """
 
 from .attributes import BaseAttribute, BaseTypedAttribute
+from .expression import Expr
 from .gobject_object import Object, ObjectContent
 from .gobject_property import Property
 from .gobject_signal import Signal

blueprintcompiler/language/expression.py

@@ -0,0 +1,63 @@
+# expressions.py
+#
+# Copyright 2022 James Westman <james@jwestman.net>
+#
+# This file is free software; you can redistribute it and/or modify it
+# under the terms of the GNU Lesser General Public License as
+# published by the Free Software Foundation; either version 3 of the
+# License, or (at your option) any later version.
+#
+# This file is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public
+# License along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
+# SPDX-License-Identifier: LGPL-3.0-or-later
+
+
+from .common import *
+
+
+expr = Pratt()
+
+
+class Expr(AstNode):
+    grammar = expr
+
+    def emit_xml(self, xml: XmlEmitter):
+        self.children[-1].emit_xml(xml)
+
+
+class InfixExpr(AstNode):
+    @property
+    def lhs(self):
+        children = list(self.parent_by_type(Expr).children)
+        return children[children.index(self) - 1]
+
+
+class IdentExpr(AstNode):
+    grammar = UseIdent("ident")
+
+    def emit_xml(self, xml: XmlEmitter):
+        xml.start_tag("constant")
+        xml.put_text(self.tokens["ident"])
+        xml.end_tag()
+
+
+class LookupOp(InfixExpr):
+    grammar = [".", UseIdent("property")]
+
+    def emit_xml(self, xml: XmlEmitter):
+        xml.start_tag("lookup", name=self.tokens["property"])
+        self.lhs.emit_xml(xml)
+        xml.end_tag()
+
+
+expr.children = [
+    Prefix(IdentExpr),
+    Prefix(["(", Expr, ")"]),
+    Infix(10, LookupOp),
+]

blueprintcompiler/language/gobject_property.py

@@ -18,6 +18,7 @@
 # SPDX-License-Identifier: LGPL-3.0-or-later
 
 
+from .expression import Expr
 from .gobject_object import Object
 from .gtkbuilder_template import Template
 from .values import Value, TranslatedStringValue
@@ -26,19 +27,27 @@ from .common import *
 
 class Property(AstNode):
     grammar = AnyOf(
-        Statement(
+        [
             UseIdent("name"),
             ":",
             Keyword("bind"),
-            UseIdent("bind_source").expected("the ID of a source object to bind from"),
+            UseIdent("bind_source"),
             ".",
-            UseIdent("bind_property").expected("a property name to bind from"),
+            UseIdent("bind_property"),
             ZeroOrMore(AnyOf(
                 ["no-sync-create", UseLiteral("no_sync_create", True)],
                 ["inverted", UseLiteral("inverted", True)],
                 ["bidirectional", UseLiteral("bidirectional", True)],
                 Match("sync-create").warn("sync-create is deprecated in favor of no-sync-create"),
             )),
+            ";",
+        ],
+        Statement(
+            UseIdent("name"),
+            UseLiteral("binding", True),
+            ":",
+            "bind",
+            Expr,
         ),
         Statement(
             UseIdent("name"),
@@ -154,7 +163,13 @@ class Property(AstNode):
             self.children[Object][0].emit_xml(xml)
             xml.end_tag()
         elif value is None:
-            xml.put_self_closing("property", **props)
+            if self.tokens["binding"]:
+                xml.start_tag("binding", **props)
+                for x in self.children:
+                    x.emit_xml(xml)
+                xml.end_tag()
+            else:
+                xml.put_self_closing("property", **props);
         else:
             xml.start_tag("property", **props)
             value.emit_xml(xml)

blueprintcompiler/parse_tree.py

@@ -98,6 +98,7 @@ class ParseContext:
     def __init__(self, tokens, index=0):
         self.tokens = list(tokens)
 
+        self.binding_power = 0
         self.index = index
         self.start = index
         self.group = None
@@ -118,6 +119,7 @@ class ParseContext:
         ctx = ParseContext(self.tokens, self.index)
         ctx.errors = self.errors
         ctx.warnings = self.warnings
+        ctx.binding_power = self.binding_power
         return ctx
 
     def apply_child(self, other):
@@ -544,6 +546,64 @@ class Keyword(ParseNode):
         return str(token) == self.kw
 
 
+class Prefix(ParseNode):
+    def __init__(self, child):
+        self.child = to_parse_node(child)
+
+    def _parse(self, ctx: ParseContext):
+        return self.child.parse(ctx).succeeded()
+
+
+class Infix(ParseNode):
+    def __init__(self, binding_power: int, child):
+        self.binding_power = binding_power
+        self.child = to_parse_node(child)
+
+    def _parse(self, ctx: ParseContext):
+        ctx.binding_power = self.binding_power
+        return self.child.parse(ctx).succeeded()
+
+    def __lt__(self, other):
+        return self.binding_power < other.binding_power
+    def __eq__(self, other):
+        return self.binding_power == other.binding_power
+
+
+class Pratt(ParseNode):
+    """ Basic Pratt parser implementation. """
+
+    def __init__(self, *children):
+        self.children = children
+
+    @property
+    def children(self):
+        return self._children
+    @children.setter
+    def children(self, children):
+        self._children = children
+        self.prefixes = [child for child in children if isinstance(child, Prefix)]
+        self.infixes = sorted([child for child in children if isinstance(child, Infix)], reverse=True)
+
+    def _parse(self, ctx: ParseContext) -> bool:
+        for prefix in self.prefixes:
+            if prefix.parse(ctx).succeeded():
+                break
+        else:
+            # none of the prefixes could be parsed
+            return False
+
+        while True:
+            succeeded = False
+            for infix in self.infixes:
+                if infix.binding_power <= ctx.binding_power:
+                    break
+                if infix.parse(ctx).succeeded():
+                    succeeded = True
+                    break
+            if not succeeded:
+                return True
+
+
 def to_parse_node(value) -> ParseNode:
     if isinstance(value, str):
         return Match(value)

tests/samples/expr_lookup.blp

@@ -0,0 +1,9 @@
+using Gtk 4.0;
+
+Overlay {
+  Label label {}
+}
+
+Label {
+  label: bind (label.parent).child.label;
+}

tests/samples/expr_lookup.ui

@@ -0,0 +1,20 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<interface>
+  <requires lib="gtk" version="4.0"/>
+  <object class="GtkOverlay">
+    <child>
+      <object class="GtkLabel" id="label"></object>
+    </child>
+  </object>
+  <object class="GtkLabel">
+    <binding name="label">
+      <lookup name="label">
+        <lookup name="child">
+          <lookup name="parent">
+            <constant>label</constant>
+          </lookup>
+        </lookup>
+      </lookup>
+    </binding>
+  </object>
+</interface>

tests/test_samples.py

@@ -136,6 +136,7 @@ class TestSamples(unittest.TestCase):
         self.assert_sample("combo_box_text")
         self.assert_sample("comments")
         self.assert_sample("enum")
+        self.assert_sample("expr_lookup")
         self.assert_sample("file_filter")
         self.assert_sample("flags")
         self.assert_sample("id_prop")