parser: Tweak parsing during error conditions

When an explicit parsing error is encountered and a CompileError raised,
apply the changes to the context state. This way, the rule that catches
the exception (e.g. Statement or Until) knows where the error occurred.

Also, changed "Expected" errors to be reported at the end of the
previous non-whitespace token.

blueprintcompiler/errors.py

@@ -92,29 +92,38 @@ class CompileError(PrintableError):
     def pretty_print(self, filename: str, code: str, stream=sys.stdout) -> None:
         assert self.range is not None
 
-        line_num, col_num = utils.idx_to_pos(self.range.start + 1, code)
-        end_line_num, end_col_num = utils.idx_to_pos(self.range.end + 1, code)
-        line = code.splitlines(True)[line_num] if code != "" else ""
+        def format_line(range: Range):
+            line_num, col_num = utils.idx_to_pos(range.start, code)
+            end_line_num, end_col_num = utils.idx_to_pos(range.end, code)
+            line = code.splitlines(True)[line_num] if code != "" else ""
 
-        # Display 1-based line numbers
-        line_num += 1
-        end_line_num += 1
+            # Display 1-based line numbers
+            line_num += 1
+            end_line_num += 1
+            col_num += 1
+            end_col_num += 1
 
-        n_spaces = col_num - 1
-        n_carets = (
-            (end_col_num - col_num)
-            if line_num == end_line_num
-            else (len(line) - n_spaces - 1)
-        )
+            n_spaces = col_num - 1
+            n_carets = (
+                (end_col_num - col_num)
+                if line_num == end_line_num
+                else (len(line) - n_spaces - 1)
+            )
 
-        n_spaces += line.count("\t", 0, col_num)
-        n_carets += line.count("\t", col_num, col_num + n_carets)
-        line = line.replace("\t", "  ")
+            n_spaces += line.count("\t", 0, col_num)
+            n_carets += line.count("\t", col_num, col_num + n_carets)
+            line = line.replace("\t", "  ")
+
+            n_carets = max(n_carets, 1)
+
+            return line_num, col_num, line.rstrip(), (" " * n_spaces) + ("^" * n_carets)
+
+        line_num, col_num, line, carets = format_line(self.range)
 
         stream.write(
             f"""{self.color}{Colors.BOLD}{self.category}: {self.message}{Colors.CLEAR}
 at {filename} line {line_num} column {col_num}:
-{Colors.FAINT}{line_num :>4} |{Colors.CLEAR}{line.rstrip()}\n     {Colors.FAINT}|{" "*n_spaces}{"^"*n_carets}{Colors.CLEAR}\n"""
+{Colors.FAINT}{line_num :>4} |{Colors.CLEAR}{line}\n     {Colors.FAINT}|{carets}{Colors.CLEAR}\n"""
         )
 
         for hint in self.hints:
@@ -139,14 +148,12 @@ at {filename} line {line_num} column {col_num}:
                 )
 
         for ref in self.references:
-            line_num, col_num = utils.idx_to_pos(ref.range.start + 1, code)
-            line = code.splitlines(True)[line_num]
-            line_num += 1
+            line_num, col_num, line, carets = format_line(ref.range)
 
             stream.write(
                 f"""{Colors.FAINT}note: {ref.message}:
 at {filename} line {line_num} column {col_num}:
-{Colors.FAINT}{line_num :>4} |{line.rstrip()}\n     {Colors.FAINT}|{" "*(col_num-1)}^{Colors.CLEAR}\n"""
+{Colors.FAINT}{line_num :>4} |{line}\n     {Colors.FAINT}|{carets}{Colors.CLEAR}\n"""
             )
 
         stream.write("\n")

blueprintcompiler/language/common.py

@@ -34,6 +34,7 @@ from ..errors import (
     CompileError,
     CompileWarning,
     DeprecatedWarning,
+    ErrorReference,
     MultipleErrors,
     UnusedWarning,
     UpgradeWarning,

blueprintcompiler/language/contexts.py

@@ -48,7 +48,7 @@ class ScopeCtx:
             return self.node
 
     @cached_property
-    def objects(self) -> T.Dict[str, Object]:
+    def objects(self) -> T.Dict[str, AstNode]:
         return {
             obj.tokens["id"]: obj
             for obj in self._iter_recursive(self.node)
@@ -58,7 +58,7 @@ class ScopeCtx:
     def validate_unique_ids(self) -> None:
         from .gtk_list_item_factory import ExtListItemFactory
 
-        passed = {}
+        passed: T.Dict[str, AstNode] = {}
         for obj in self._iter_recursive(self.node):
             if obj.tokens["id"] is None:
                 continue
@@ -71,10 +71,16 @@ class ScopeCtx:
                     raise CompileError(
                         f"Duplicate object ID '{obj.tokens['id']}'",
                         token.range,
+                        references=[
+                            ErrorReference(
+                                passed[obj.tokens["id"]].group.tokens["id"].range,
+                                "previous declaration was here",
+                            )
+                        ],
                     )
             passed[obj.tokens["id"]] = obj
 
-    def _iter_recursive(self, node: AstNode):
+    def _iter_recursive(self, node: AstNode) -> T.Generator[AstNode, T.Any, None]:
         yield node
         for child in node.children:
             if child.context[ScopeCtx] is self:

blueprintcompiler/parse_tree.py

@@ -235,7 +235,15 @@ class ParseNode:
         start_idx = ctx.index
         inner_ctx = ctx.create_child()
 
-        if self._parse(inner_ctx):
+        try:
+            result = self._parse(inner_ctx)
+        except Exception as e:
+            # If an exception occurs, there's an explicit error, not just a rule that didn't match. Apply the context
+            # state so that whichever rule handles the exception (e.g. a Statement) knows where the error occurred.
+            ctx.apply_child(inner_ctx)
+            raise e
+
+        if result:
             ctx.apply_child(inner_ctx)
             if ctx.index == start_idx:
                 return ParseResult.EMPTY
@@ -269,11 +277,11 @@ class Err(ParseNode):
         if self.child.parse(ctx).failed():
             start_idx = ctx.start
             while ctx.tokens[start_idx].type in SKIP_TOKENS:
-                start_idx += 1
+                start_idx -= 1
             start_token = ctx.tokens[start_idx]
 
             raise CompileError(
-                self.message, Range(start_token.start, start_token.start, ctx.text)
+                self.message, Range(start_token.end, start_token.end, ctx.text)
             )
         return True
 
@@ -350,7 +358,20 @@ class Statement(ParseNode):
 
         token = ctx.peek_token()
         if str(token) != self.end:
-            ctx.errors.append(CompileError(f"Expected `{self.end}`", token.range))
+            start_idx = ctx.index - 1
+            while ctx.tokens[start_idx].type in SKIP_TOKENS:
+                start_idx -= 1
+            start_token = ctx.tokens[start_idx]
+
+            position = (
+                start_token.start if ctx.index - 1 == start_idx else start_token.end
+            )
+
+            ctx.errors.append(
+                CompileError(
+                    f"Expected `{self.end}`", Range(position, position, ctx.text)
+                )
+            )
         else:
             ctx.next_token()
         return True
@@ -411,7 +432,6 @@ class Until(ParseNode):
                         ctx.skip_unexpected_token()
             except CompileError as e:
                 ctx.errors.append(e)
-                ctx.next_token()
 
         return True
 

tests/sample_errors/empty.err

@@ -1 +1 @@
-1,0,0,File must start with a "using Gtk" directive (e.g. `using Gtk 4.0;`)
+1,1,0,File must start with a "using Gtk" directive (e.g. `using Gtk 4.0;`)

tests/sample_errors/expected_semicolon.err

@@ -1 +1 @@
-6,1,1,Expected `;`
+5,4,0,Expected `;`

tests/sample_errors/incomplete_signal.err

@@ -1,2 +1 @@
-5,1,0,Expected a signal detail name
-4,9,3,Unexpected tokens
+4,11,0,Expected a signal detail name

tests/sample_errors/menu_toplevel_attribute.err

@@ -1,2 +1 @@
-4,5,21,Attributes are not permitted at the top level of a menu
-4,16,10,Unexpected tokens
+4,5,21,Attributes are not permitted at the top level of a menu

tests/sample_errors/no_import_version.err

@@ -1 +1 @@
-1,11,0,Expected a version number for GTK
+1,10,0,Expected a version number for GTK

tests/test_samples.py

@@ -143,9 +143,9 @@ class TestSamples(unittest.TestCase):
             ]
 
             def error_str(error: CompileError):
-                line, col = utils.idx_to_pos(error.range.start + 1, blueprint)
+                line, col = utils.idx_to_pos(error.range.start, blueprint)
                 len = error.range.length
-                return ",".join([str(line + 1), str(col), str(len), error.message])
+                return ",".join([str(line + 1), str(col + 1), str(len), error.message])
 
             actual = "\n".join([error_str(error) for error in errors])