Ensure that diagnostic position cannot be less than 0

Resolves pappasam#272

Author: pappasam

jedi_language_server/initialization_options.py

@@ -141,7 +141,7 @@ def structure(cls: type) -> Any:
     return make_dict_structure_fn(
         cls,
         initialization_options_converter,
-        **{
+        **{  # type: ignore[arg-type]
             a.name: override(rename=convert_class_keys(a.name))
             for a in fields(cls)
         },

jedi_language_server/jedi_utils.py

@@ -16,7 +16,14 @@
 import jedi.inference.references
 import jedi.settings
 from jedi import Project, Script
-from jedi.api.classes import BaseName, Completion, Name, ParamName, Signature
+from jedi.api.classes import (
+    BaseName,
+    BaseSignature,
+    Completion,
+    Name,
+    ParamName,
+    Signature,
+)
 from lsprotocol.types import (
     CompletionItem,
     CompletionItemKind,
@@ -298,21 +305,19 @@ def lsp_python_diagnostic(uri: str, source: str) -> Optional[Diagnostic]:
         compile(source, uri, "exec", PyCF_ONLY_AST)
         return None
     except SyntaxError as err:
-        column = err.offset - 1 if err.offset is not None else 0
-        line = err.lineno - 1 if err.lineno is not None else 0
-
+        column = max(0, err.offset - 1 if err.offset is not None else 0)
+        line = max(0, err.lineno - 1 if err.lineno is not None else 0)
         _until_column = getattr(err, "end_offset", None)
         _until_line = getattr(err, "end_lineno", None)
-
-        until_column = (
-            _until_column - 1 if _until_column is not None else column + 1
+        until_column = max(
+            0, _until_column - 1 if _until_column is not None else column + 1
+        )
+        until_line = max(
+            0, _until_line - 1 if _until_line is not None else line
         )
-        until_line = _until_line - 1 if _until_line is not None else line
-
         if (line, column) >= (until_line, until_column):
             until_column, until_line = column, line
             column = 0
-
         return Diagnostic(
             range=Range(
                 start=Position(line=line, character=column),
@@ -419,7 +424,7 @@ def clean_completion_name(name: str, char_before_cursor: str) -> str:
 _PARAM_NAME_IGNORE = {"/", "*"}
 
 
-def get_snippet_signature(signature: Signature) -> str:
+def get_snippet_signature(signature: Signature | BaseSignature) -> str:
     """Return the snippet signature."""
     params: List[ParamName] = signature.params
     if not params:
@@ -527,11 +532,6 @@ def _md_bold(value: str, markup_kind: MarkupKind) -> str:
     return f"**{value}**" if markup_kind == MarkupKind.Markdown else value
 
 
-def _md_italic(value: str, markup_kind: MarkupKind) -> str:
-    """Add italic surrounding when markup_kind is markdown."""
-    return f"*{value}*" if markup_kind == MarkupKind.Markdown else value
-
-
 def _md_text(value: str, markup_kind: MarkupKind) -> str:
     """Surround a markdown string with a Python fence."""
     return (