From 300578fe808a6a58deb5cb58b63704e87032a24f 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: Tue, 16 Jan 2024 17:29:18 +0000
Subject: [PATCH 1/6] Add function that validates identifiers.

---
 src/textual/css/errors.py |  4 ++++
 src/textual/css/parse.py  | 32 ++++++++++++++++++++++++++++++--
 2 files changed, 34 insertions(+), 2 deletions(-)

diff --git a/src/textual/css/errors.py b/src/textual/css/errors.py
index 815b11394e..79873692ee 100644
--- a/src/textual/css/errors.py
+++ b/src/textual/css/errors.py
@@ -48,3 +48,7 @@ def __rich_console__(
 
 class StylesheetError(Exception):
     pass
+
+
+class InvalidIDError(Exception):
+    """For when invalid identifiers are used."""
diff --git a/src/textual/css/parse.py b/src/textual/css/parse.py
index b9e59d94ba..28aa3e26f5 100644
--- a/src/textual/css/parse.py
+++ b/src/textual/css/parse.py
@@ -1,13 +1,14 @@
 from __future__ import annotations
 
 import dataclasses
+import re
 from functools import lru_cache
 from typing import Iterable, Iterator, NoReturn
 
 from ..suggestions import get_suggestion
 from ._help_renderables import HelpText
 from ._styles_builder import DeclarationError, StylesBuilder
-from .errors import UnresolvedVariableError
+from .errors import InvalidIDError, UnresolvedVariableError
 from .model import (
     CombinatorType,
     Declaration,
@@ -17,7 +18,13 @@
     SelectorType,
 )
 from .styles import Styles
-from .tokenize import Token, tokenize, tokenize_declarations, tokenize_values
+from .tokenize import (
+    IDENTIFIER,
+    Token,
+    tokenize,
+    tokenize_declarations,
+    tokenize_values,
+)
 from .tokenizer import EOFError, ReferencedBy
 from .types import CSSLocation, Specificity3
 
@@ -52,6 +59,27 @@ def _add_specificity(
     return (a1 + a2, b1 + b2, c1 + c2)
 
 
+_IDENTIFIER_REGEX = re.compile(f"^{IDENTIFIER}$")
+"""Regular expression that matches strings that contain valid identifiers."""
+
+
+def validate_identifier(identifier: str) -> str:
+    """Determines whether the given identifier is valid or not.
+
+    Args:
+        identifier: Identifier to validate.
+
+    Returns:
+        The identifier, if it is valid.
+
+    Raises:
+        InvalidIDError: If the identifier is invalid.
+    """
+    if _IDENTIFIER_REGEX.match(identifier) is None:
+        raise InvalidIDError(f"{identifier!r} is not a valid identifier.")
+    return identifier
+
+
 @lru_cache(maxsize=1024)
 def parse_selectors(css_selectors: str) -> tuple[SelectorSet, ...]:
     if not css_selectors.strip():

From 5f0af2da473a50632e5da8453509edb332adb2aa 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: Tue, 16 Jan 2024 17:30:14 +0000
Subject: [PATCH 2/6] Validate IDs when creating DOM nodes.

---
 src/textual/dom.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/textual/dom.py b/src/textual/dom.py
index 461e9acea7..c5124ae9c8 100644
--- a/src/textual/dom.py
+++ b/src/textual/dom.py
@@ -38,7 +38,7 @@
 from .css._error_tools import friendly_list
 from .css.constants import VALID_DISPLAY, VALID_VISIBILITY
 from .css.errors import DeclarationError, StyleValueError
-from .css.parse import parse_declarations
+from .css.parse import parse_declarations, validate_identifier
 from .css.styles import RenderStyles, Styles
 from .css.tokenize import IDENTIFIER
 from .message_pump import MessagePump
@@ -170,7 +170,7 @@ def __init__(
         self._name = name
         self._id = None
         if id is not None:
-            self.id = id
+            self.id = validate_identifier(id)
 
         _classes = classes.split() if classes else []
         check_identifiers("class name", *_classes)

From 2d0591af0096b683f9624f0e9df06cb7d375822b 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: Tue, 16 Jan 2024 17:30:24 +0000
Subject: [PATCH 3/6] Add regression tests.

---
 CHANGELOG.md            |  1 +
 tests/css/test_parse.py | 41 +++++++++++++++++++++++++++++++++++++++--
 tests/test_dom.py       | 23 ++++++++++++++++++++++-
 3 files changed, 62 insertions(+), 3 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index d3f838be7d..f16ac4dbe3 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -26,6 +26,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 - `SelectionList` option IDs are usable as soon as the widget is instantiated https://github.com/Textualize/textual/issues/3903
 - Fix issue with `Strip.crop` when crop window start aligned with strip end https://github.com/Textualize/textual/pull/3998
 - Fixed Strip.crop_extend https://github.com/Textualize/textual/pull/4011
+- Widgets could be created with IDs that you couldn't query back https://github.com/Textualize/textual/issues/3954
 
 
 ## [0.47.1] - 2023-01-05
diff --git a/tests/css/test_parse.py b/tests/css/test_parse.py
index febe4f06bb..2d6aeef002 100644
--- a/tests/css/test_parse.py
+++ b/tests/css/test_parse.py
@@ -3,8 +3,8 @@
 import pytest
 
 from textual.color import Color
-from textual.css.errors import UnresolvedVariableError
-from textual.css.parse import substitute_references
+from textual.css.errors import InvalidIDError, UnresolvedVariableError
+from textual.css.parse import substitute_references, validate_identifier
 from textual.css.scalar import Scalar, Unit
 from textual.css.stylesheet import Stylesheet, StylesheetParseError
 from textual.css.tokenize import tokenize
@@ -1272,3 +1272,40 @@ def test_parse_bad_pseudo_selector_with_suggestion():
         stylesheet.parse()
 
     assert error.value.start == (2, 7)
+
+
+@pytest.mark.parametrize(
+    "identifier",
+    [
+        "the",
+        "quick",
+        "brown",
+        "f0x",
+        "jump5",
+        "ov3r",
+        "_the__",
+        "l4zy_",
+        "_d0g",
+    ],
+)
+def test_identifier_validation_passes(identifier: str):
+    assert validate_identifier(identifier) == identifier
+
+
+@pytest.mark.parametrize(
+    "identifier",
+    [
+        " the",
+        "quick ",
+        "bro wn",
+        "f0x&",
+        "+jump5",
+        "0v3r",
+        "—the",
+        "läzy_",
+        "_d0g!",
+    ],
+)
+def test_identifier_validation_fails(identifier: str):
+    with pytest.raises(InvalidIDError):
+        validate_identifier(identifier)
diff --git a/tests/test_dom.py b/tests/test_dom.py
index 6f06fb8091..d4dc4336dd 100644
--- a/tests/test_dom.py
+++ b/tests/test_dom.py
@@ -1,6 +1,6 @@
 import pytest
 
-from textual.css.errors import StyleValueError
+from textual.css.errors import InvalidIDError, StyleValueError
 from textual.dom import BadIdentifier, DOMNode
 
 
@@ -259,3 +259,24 @@ def test_walk_children_with_self_breadth(search):
     ]
 
     assert children == ["f", "e", "d", "c", "b", "a"]
+
+
+@pytest.mark.parametrize(
+    "identifier",
+    [
+        " bad",
+        "  terrible  ",
+        "worse!  ",
+        "&ampersand",
+        "amper&sand",
+        "ampersand&",
+        "2_leading_digits",
+        "água",  # water
+        "cão",  # dog
+        "@'/.23",
+    ],
+)
+def test_id_validation(identifier: str):
+    """Regression test for https://github.com/Textualize/textual/issues/3954."""
+    with pytest.raises(InvalidIDError):
+        DOMNode(id=identifier)

From 27408a0ff74086ab28b3dbcaa0d3b829a467922c 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: Tue, 16 Jan 2024 17:40:21 +0000
Subject: [PATCH 4/6] Removes my duplicate work.

This reverts commit 300578fe808a6a58deb5cb58b63704e87032a24f and a couple of other things that I really didn't need.
---
 src/textual/css/errors.py |  4 ----
 src/textual/css/parse.py  | 32 ++----------------------------
 tests/css/test_parse.py   | 41 ++-------------------------------------
 tests/test_dom.py         |  2 +-
 4 files changed, 5 insertions(+), 74 deletions(-)

diff --git a/src/textual/css/errors.py b/src/textual/css/errors.py
index 79873692ee..815b11394e 100644
--- a/src/textual/css/errors.py
+++ b/src/textual/css/errors.py
@@ -48,7 +48,3 @@ def __rich_console__(
 
 class StylesheetError(Exception):
     pass
-
-
-class InvalidIDError(Exception):
-    """For when invalid identifiers are used."""
diff --git a/src/textual/css/parse.py b/src/textual/css/parse.py
index 28aa3e26f5..b9e59d94ba 100644
--- a/src/textual/css/parse.py
+++ b/src/textual/css/parse.py
@@ -1,14 +1,13 @@
 from __future__ import annotations
 
 import dataclasses
-import re
 from functools import lru_cache
 from typing import Iterable, Iterator, NoReturn
 
 from ..suggestions import get_suggestion
 from ._help_renderables import HelpText
 from ._styles_builder import DeclarationError, StylesBuilder
-from .errors import InvalidIDError, UnresolvedVariableError
+from .errors import UnresolvedVariableError
 from .model import (
     CombinatorType,
     Declaration,
@@ -18,13 +17,7 @@
     SelectorType,
 )
 from .styles import Styles
-from .tokenize import (
-    IDENTIFIER,
-    Token,
-    tokenize,
-    tokenize_declarations,
-    tokenize_values,
-)
+from .tokenize import Token, tokenize, tokenize_declarations, tokenize_values
 from .tokenizer import EOFError, ReferencedBy
 from .types import CSSLocation, Specificity3
 
@@ -59,27 +52,6 @@ def _add_specificity(
     return (a1 + a2, b1 + b2, c1 + c2)
 
 
-_IDENTIFIER_REGEX = re.compile(f"^{IDENTIFIER}$")
-"""Regular expression that matches strings that contain valid identifiers."""
-
-
-def validate_identifier(identifier: str) -> str:
-    """Determines whether the given identifier is valid or not.
-
-    Args:
-        identifier: Identifier to validate.
-
-    Returns:
-        The identifier, if it is valid.
-
-    Raises:
-        InvalidIDError: If the identifier is invalid.
-    """
-    if _IDENTIFIER_REGEX.match(identifier) is None:
-        raise InvalidIDError(f"{identifier!r} is not a valid identifier.")
-    return identifier
-
-
 @lru_cache(maxsize=1024)
 def parse_selectors(css_selectors: str) -> tuple[SelectorSet, ...]:
     if not css_selectors.strip():
diff --git a/tests/css/test_parse.py b/tests/css/test_parse.py
index 2d6aeef002..febe4f06bb 100644
--- a/tests/css/test_parse.py
+++ b/tests/css/test_parse.py
@@ -3,8 +3,8 @@
 import pytest
 
 from textual.color import Color
-from textual.css.errors import InvalidIDError, UnresolvedVariableError
-from textual.css.parse import substitute_references, validate_identifier
+from textual.css.errors import UnresolvedVariableError
+from textual.css.parse import substitute_references
 from textual.css.scalar import Scalar, Unit
 from textual.css.stylesheet import Stylesheet, StylesheetParseError
 from textual.css.tokenize import tokenize
@@ -1272,40 +1272,3 @@ def test_parse_bad_pseudo_selector_with_suggestion():
         stylesheet.parse()
 
     assert error.value.start == (2, 7)
-
-
-@pytest.mark.parametrize(
-    "identifier",
-    [
-        "the",
-        "quick",
-        "brown",
-        "f0x",
-        "jump5",
-        "ov3r",
-        "_the__",
-        "l4zy_",
-        "_d0g",
-    ],
-)
-def test_identifier_validation_passes(identifier: str):
-    assert validate_identifier(identifier) == identifier
-
-
-@pytest.mark.parametrize(
-    "identifier",
-    [
-        " the",
-        "quick ",
-        "bro wn",
-        "f0x&",
-        "+jump5",
-        "0v3r",
-        "—the",
-        "läzy_",
-        "_d0g!",
-    ],
-)
-def test_identifier_validation_fails(identifier: str):
-    with pytest.raises(InvalidIDError):
-        validate_identifier(identifier)
diff --git a/tests/test_dom.py b/tests/test_dom.py
index d4dc4336dd..5026f0ab07 100644
--- a/tests/test_dom.py
+++ b/tests/test_dom.py
@@ -1,6 +1,6 @@
 import pytest
 
-from textual.css.errors import InvalidIDError, StyleValueError
+from textual.css.errors import StyleValueError
 from textual.dom import BadIdentifier, DOMNode
 
 

From 0db8e6d6c06a88f4d523f14ff83b776969513b3e 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: Tue, 16 Jan 2024 17:50:47 +0000
Subject: [PATCH 5/6] Fix regular expression check for identifiers.

---
 CHANGELOG.md       | 2 +-
 src/textual/dom.py | 6 +++---
 tests/test_dom.py  | 4 ++--
 3 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index f16ac4dbe3..42dcff82e1 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -26,7 +26,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 - `SelectionList` option IDs are usable as soon as the widget is instantiated https://github.com/Textualize/textual/issues/3903
 - Fix issue with `Strip.crop` when crop window start aligned with strip end https://github.com/Textualize/textual/pull/3998
 - Fixed Strip.crop_extend https://github.com/Textualize/textual/pull/4011
-- Widgets could be created with IDs that you couldn't query back https://github.com/Textualize/textual/issues/3954
+- ID and class validation was too lenient https://github.com/Textualize/textual/issues/3954
 
 
 ## [0.47.1] - 2023-01-05
diff --git a/src/textual/dom.py b/src/textual/dom.py
index c5124ae9c8..92a9e6e18c 100644
--- a/src/textual/dom.py
+++ b/src/textual/dom.py
@@ -38,7 +38,7 @@
 from .css._error_tools import friendly_list
 from .css.constants import VALID_DISPLAY, VALID_VISIBILITY
 from .css.errors import DeclarationError, StyleValueError
-from .css.parse import parse_declarations, validate_identifier
+from .css.parse import parse_declarations
 from .css.styles import RenderStyles, Styles
 from .css.tokenize import IDENTIFIER
 from .message_pump import MessagePump
@@ -62,7 +62,7 @@
 
 from typing_extensions import Literal
 
-_re_identifier = re.compile(IDENTIFIER)
+_re_identifier = re.compile(f"^{IDENTIFIER}$")
 
 
 WalkMethod: TypeAlias = Literal["depth", "breadth"]
@@ -170,7 +170,7 @@ def __init__(
         self._name = name
         self._id = None
         if id is not None:
-            self.id = validate_identifier(id)
+            self.id = id
 
         _classes = classes.split() if classes else []
         check_identifiers("class name", *_classes)
diff --git a/tests/test_dom.py b/tests/test_dom.py
index 5026f0ab07..ea14a25bfe 100644
--- a/tests/test_dom.py
+++ b/tests/test_dom.py
@@ -277,6 +277,6 @@ def test_walk_children_with_self_breadth(search):
     ],
 )
 def test_id_validation(identifier: str):
-    """Regression test for https://github.com/Textualize/textual/issues/3954."""
-    with pytest.raises(InvalidIDError):
+    """Regression tests for https://github.com/Textualize/textual/issues/3954."""
+    with pytest.raises(BadIdentifier):
         DOMNode(id=identifier)

From 98e28f0dcd6debb058c36fe1f269139d93aa8294 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: Wed, 17 Jan 2024 11:10:43 +0000
Subject: [PATCH 6/6] Use 're.fullmatch' instead of anchors.

Relevant review comment: https://github.com/Textualize/textual/pull/4032#discussion_r1453831415.
---
 src/textual/dom.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/textual/dom.py b/src/textual/dom.py
index 92a9e6e18c..2664881d91 100644
--- a/src/textual/dom.py
+++ b/src/textual/dom.py
@@ -62,7 +62,7 @@
 
 from typing_extensions import Literal
 
-_re_identifier = re.compile(f"^{IDENTIFIER}$")
+_re_identifier = re.compile(IDENTIFIER)
 
 
 WalkMethod: TypeAlias = Literal["depth", "breadth"]
@@ -80,7 +80,7 @@ def check_identifiers(description: str, *names: str) -> None:
         description: Description of where identifier is used for error message.
         *names: Identifiers to check.
     """
-    match = _re_identifier.match
+    match = _re_identifier.fullmatch
     for name in names:
         if match(name) is None:
             raise BadIdentifier(