Better error handling for incomplete syntax

gtkblueprinttool/ast.py

@@ -37,6 +37,7 @@ class AstNode:
         self.group = None
         self.parent = None
         self.child_nodes = None
+        self.incomplete = False
 
     def __init_subclass__(cls):
         cls.completers = []
@@ -148,9 +149,9 @@ class GtkDirective(AstNode):
         else:
             err = CompileError("Only GTK 4 is supported")
             if self.version.startswith("4"):
-                err.hint("Expected the GIR version, not an exact version number. Use `@gtk \"4.0\";`.")
+                err.hint("Expected the GIR version, not an exact version number. Use `using Gtk 4.0;`.")
             else:
-                err.hint("Expected `@gtk \"4.0\";`")
+                err.hint("Expected `using Gtk 4.0;`")
             raise err
 
     def emit_xml(self, xml: XmlEmitter):

gtkblueprinttool/ast_utils.py

@@ -45,6 +45,11 @@ class Validator:
                 # same message again
                 instance.__dict__[key + "_err"] = True
 
+                # If the node is only partially complete, then an error must
+                # have already been reported at the parsing stage
+                if instance.incomplete:
+                    return None
+
                 # This mess of code sets the error's start and end positions
                 # from the tokens passed to the decorator, if they have not
                 # already been set
@@ -58,6 +63,13 @@ class Validator:
 
                 # Re-raise the exception
                 raise e
+            except Exception as e:
+                # If the node is only partially complete, then an error must
+                # have already been reported at the parsing stage
+                if instance.incomplete:
+                    return None
+                else:
+                    raise e
 
         # Return the validation result (which other validators, or the code
         # generation phase, might depend on)

gtkblueprinttool/parse_tree.py

@@ -66,6 +66,7 @@ class ParseGroup:
         self.tokens: T.Dict[str, Token] = {}
         self.start = start
         self.end = None
+        self.incomplete = False
 
     def add_child(self, child):
         child_type = child.ast_type.child_type
@@ -85,12 +86,16 @@ class ParseGroup:
             child_type: [child.to_ast() for child in children]
             for child_type, children in self.children.items()
         }
+
         try:
             ast = self.ast_type(**children, **self.keys)
+            ast.incomplete = self.incomplete
             ast.group = self
             ast.child_nodes = [c for child_type in children.values() for c in child_type]
+
             for child in ast.child_nodes:
                 child.parent = ast
+
             return ast
         except TypeError as e:
             raise CompilerBugError(f"Failed to construct ast.{self.ast_type.__name__} from ParseGroup. See the previous stacktrace.")
@@ -114,6 +119,7 @@ class ParseContext:
         self.group_keys = {}
         self.group_children = []
         self.last_group = None
+        self.group_incomplete = True
 
         self.errors = []
         self.warnings = []
@@ -140,12 +146,14 @@ class ParseContext:
             for child in other.group_children:
                 other.group.add_child(child)
             other.group.end = other.tokens[other.index - 1].end
+            other.group.incomplete = other.group_incomplete
             self.group_children.append(other.group)
         else:
             # If the other context had no match group of its own, collect all
             # its matched values
             self.group_keys = {**self.group_keys, **other.group_keys}
             self.group_children += other.group_children
+            self.group_incomplete |= other.group_incomplete
 
         self.index = other.index
         # Propagate the last parsed group down the stack so it can be easily
@@ -166,6 +174,12 @@ class ParseContext:
         assert_true(key not in self.group_keys)
         self.group_keys[key] = (value, token)
 
+    def set_group_incomplete(self):
+        """ Marks the current match group as incomplete (it could not be fully
+        parsed, but the parser recovered). """
+        assert_true(key not in self.group_keys)
+        self.group_incomplete = True
+
 
     def skip(self):
         """ Skips whitespace and comments. """
@@ -295,6 +309,7 @@ class Statement(ParseNode):
                     return False
             except CompileError as e:
                 ctx.errors.append(e)
+                ctx.group
                 return True
 
         token = ctx.peek_token()

gtkblueprinttool/parser.py

@@ -30,8 +30,8 @@ def parse(tokens) -> T.Tuple[ast.UI, T.Optional[MultipleErrors]]:
     gtk_directive = Group(
         ast.GtkDirective,
         Statement(
-            Keyword("using").err("File must start with a \"using gtk\" directive (e.g. `using Gtk 4.0;`)"),
-            Keyword("Gtk").err("File must start with a \"using gtk\" directive (e.g. `using Gtk 4.0;`)"),
+            Keyword("using").err("File must start with a \"using Gtk\" directive (e.g. `using Gtk 4.0;`)"),
+            Keyword("Gtk").err("File must start with a \"using Gtk\" directive (e.g. `using Gtk 4.0;`)"),
             UseNumberText("version").expected("a version number for GTK"),
         )
     )
@@ -298,7 +298,7 @@ def parse(tokens) -> T.Tuple[ast.UI, T.Optional[MultipleErrors]]:
     ui = Group(
         ast.UI,
         Sequence(
-            gtk_directive.err("File must start with a \"using Gtk\" directive (e.g. `using Gtk 4.0;`)"),
+            gtk_directive,
             ZeroOrMore(import_statement),
             Until(AnyOf(
                 template,