From c1204bbf5a92acec43db61da84701c3bdec4640e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Rodrigo=20Gir=C3=A3o=20Serr=C3=A3o?=
 <5621605+rodrigogiraoserrao@users.noreply.github.com>
Date: Thu, 9 Nov 2023 17:48:39 +0000
Subject: [PATCH] Be consistent with line/col numbers.

I added some comments so that we know what line/column numbers are 0-based and which ones are 1-based.

Related issue: #3625.
---
 CHANGELOG.md                 |  1 +
 src/textual/css/tokenizer.py | 29 +++++++++++++++++------------
 tests/css/test_parse.py      | 24 +++++++++++++++++++++---
 3 files changed, 39 insertions(+), 15 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index f82cf3a40f..4bad66e340 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -14,6 +14,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 - Added missing `blur` pseudo class https://github.com/Textualize/textual/issues/3439
 - Fixed visual glitched characters on Windows due to Python limitation https://github.com/Textualize/textual/issues/2548
 - Fixed live-reloading of screen CSS https://github.com/Textualize/textual/issues/3454
+- Off-by-one in CSS error reporting https://github.com/Textualize/textual/issues/3625
 
 ### Changed
 
diff --git a/src/textual/css/tokenizer.py b/src/textual/css/tokenizer.py
index d7cfc449d3..875537eb7e 100644
--- a/src/textual/css/tokenizer.py
+++ b/src/textual/css/tokenizer.py
@@ -34,9 +34,9 @@ def __init__(
         Args:
             read_from: The location where the CSS was read from.
             code: The code being parsed.
-            start: Line number of the error.
+            start: Line and column number of the error (1-indexed).
             message: A message associated with the error.
-            end: End location of token, or None if not known.
+            end: End location of token (1-indexed), or None if not known.
         """
 
         self.read_from = read_from
@@ -60,9 +60,13 @@ def _get_snippet(self) -> Panel:
             line_numbers=True,
             indent_guides=True,
             line_range=(max(0, line_no - 2), line_no + 2),
-            highlight_lines={line_no + 1},
+            highlight_lines={line_no},
+        )
+        syntax.stylize_range(
+            "reverse bold",
+            (self.start[0], self.start[1] - 1),
+            (self.end[0], self.end[1] - 1),
         )
-        syntax.stylize_range("reverse bold", self.start, self.end)
         return Panel(syntax, border_style="red")
 
     def __rich__(self) -> RenderableType:
@@ -136,19 +140,20 @@ class Token(NamedTuple):
     read_from: CSSLocation
     code: str
     location: tuple[int, int]
+    """Token starting location, 0-indexed."""
     referenced_by: ReferencedBy | None = None
 
     @property
     def start(self) -> tuple[int, int]:
-        """Start line and column (1 indexed)."""
+        """Start line and column (1-indexed)."""
         line, offset = self.location
-        return (line + 1, offset)
+        return (line + 1, offset + 1)
 
     @property
     def end(self) -> tuple[int, int]:
-        """End line and column (1 indexed)."""
+        """End line and column (1-indexed)."""
         line, offset = self.location
-        return (line + 1, offset + len(self.value))
+        return (line + 1, offset + len(self.value) + 1)
 
     def with_reference(self, by: ReferencedBy | None) -> "Token":
         """Return a copy of the Token, with reference information attached.
@@ -199,7 +204,7 @@ def get_token(self, expect: Expect) -> Token:
                     "",
                     self.read_from,
                     self.code,
-                    (line_no + 1, col_no + 1),
+                    (line_no, col_no),
                     None,
                 )
             else:
@@ -217,7 +222,7 @@ def get_token(self, expect: Expect) -> Token:
             raise TokenError(
                 self.read_from,
                 self.code,
-                (line_no, col_no),
+                (line_no + 1, col_no + 1),
                 message,
             )
         iter_groups = iter(match.groups())
@@ -251,14 +256,14 @@ def get_token(self, expect: Expect) -> Token:
                 raise TokenError(
                     self.read_from,
                     self.code,
-                    (line_no, col_no),
+                    (line_no + 1, col_no + 1),
                     f"unknown pseudo-class {pseudo_class!r}; did you mean {suggestion!r}?; {all_valid}",
                 )
             else:
                 raise TokenError(
                     self.read_from,
                     self.code,
-                    (line_no, col_no),
+                    (line_no + 1, col_no + 1),
                     f"unknown pseudo-class {pseudo_class!r}; {all_valid}",
                 )
 
diff --git a/tests/css/test_parse.py b/tests/css/test_parse.py
index 124f820d53..febe4f06bb 100644
--- a/tests/css/test_parse.py
+++ b/tests/css/test_parse.py
@@ -1238,7 +1238,7 @@ def test_combined_type_starts_with_number(self):
                 stylesheet.parse()
 
 
-def test_parse_bad_psuedo_selector():
+def test_parse_bad_pseudo_selector():
     """Check unknown selector raises a token error."""
 
     bad_selector = """\
@@ -1248,9 +1248,27 @@ def test_parse_bad_psuedo_selector():
     """
 
     stylesheet = Stylesheet()
-    stylesheet.add_source(bad_selector, "foo")
+    stylesheet.add_source(bad_selector, None)
 
     with pytest.raises(TokenError) as error:
         stylesheet.parse()
 
-    assert error.value.start == (0, 6)
+    assert error.value.start == (1, 7)
+
+
+def test_parse_bad_pseudo_selector_with_suggestion():
+    """Check unknown pseudo selector raises token error with correct position."""
+
+    bad_selector = """
+Widget:blu {
+    border: red;
+}
+"""
+
+    stylesheet = Stylesheet()
+    stylesheet.add_source(bad_selector, None)
+
+    with pytest.raises(TokenError) as error:
+        stylesheet.parse()
+
+    assert error.value.start == (2, 7)