Implement `flake8_todos` (#3921)

LICENSE

@@ -354,6 +354,37 @@ are:
     SOFTWARE.
   """
 
+- flake8-todos, licensed as follows:
+  """
+    Copyright (c) 2019 EclecticIQ. All rights reserved.
+    Copyright (c) 2020 Gram <gram@orsinium.dev>. All rights reserved.
+
+    Redistribution and use in source and binary forms, with or without
+    modification, are permitted provided that the following conditions are met:
+
+       1. Redistributions of source code must retain the above copyright notice,
+    this list of conditions and the following disclaimer.
+
+       2. Redistributions in binary form must reproduce the above copyright
+    notice, this list of conditions and the following disclaimer in the
+    documentation and/or other materials provided with the distribution.
+
+       3. Neither the name of the copyright holder nor the names of its
+    contributors may be used to endorse or promote products derived from this
+    software without specific prior written permission.
+
+    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+    AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+    IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+    DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+    FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+    DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+    SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+    CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+    OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+    OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+  """
+
 - flake8-unused-arguments, licensed as follows:
   """
     MIT License

README.md

@@ -279,6 +279,7 @@ quality tools, including:
 - [flake8-simplify](https://pypi.org/project/flake8-simplify/)
 - [flake8-super](https://pypi.org/project/flake8-super/)
 - [flake8-tidy-imports](https://pypi.org/project/flake8-tidy-imports/)
+- [flake8-todos](https://pypi.org/project/flake8-todos/)
 - [flake8-type-checking](https://pypi.org/project/flake8-type-checking/)
 - [flake8-use-pathlib](https://pypi.org/project/flake8-use-pathlib/)
 - [flynt](https://pypi.org/project/flynt/) ([#2102](https://github.com/charliermarsh/ruff/issues/2102))

crates/ruff/resources/test/fixtures/flake8_todos/TD001.py

@@ -0,0 +1,8 @@
+# T001 - accepted
+# TODO (evanrittenhouse): this is a valid TODO
+# SOME_OTHER_TAG: this is impossible to determine
+# this is not a TODO
+
+# T001 - errors
+# XXX (evanrittenhouse): this is not fine
+# FIXME (evanrittenhouse): this is not fine

crates/ruff/resources/test/fixtures/flake8_todos/TD002.py

@@ -0,0 +1,7 @@
+# T002 - accepted
+# TODO (evanrittenhouse): this has an author
+# TODO(evanrittenhouse): this also has an author
+# T002 - errors
+# TODO: this has no author
+# FIXME: neither does this
+# TODO : and neither does this

crates/ruff/resources/test/fixtures/flake8_todos/TD003.py

@@ -0,0 +1,29 @@
+# TDO003 - accepted
+# TODO: this comment has a link
+# https://github.com/charliermarsh/ruff/issues/3870
+
+# TODO: this comment has an issue
+# TDO-3870
+
+# TDO003 - errors
+# TODO: this comment has no
+# link after it
+
+# TODO: here's a TODO with no link after it
+def foo(x):
+    return x
+
+# TODO: here's a TODO on the last line with no link
+# Here's more content.
+# TDO-3870
+
+# TODO: here's a TODO on the last line with no link
+# Here's more content, with a space.
+
+# TDO-3870
+
+# TODO: here's a TODO without an issue link
+# TODO: followed by a new TODO with an issue link
+# TDO-3870
+
+# TODO: here's a TODO on the last line with no link

crates/ruff/resources/test/fixtures/flake8_todos/TD004.py

@@ -0,0 +1,6 @@
+# T004 - accepted
+# TODO(evanrittenhouse): this has a colon
+# T004 - errors
+# TODO this has no colon
+# TODO(evanrittenhouse 😀) this has no colon
+# FIXME add a colon

crates/ruff/resources/test/fixtures/flake8_todos/TD005.py

@@ -0,0 +1,6 @@
+# T005 - accepted
+# TODO(evanrittenhouse): this has text, while the errors do not
+# T005 - errors
+# TODO(evanrittenhouse):
+# TODO(evanrittenhouse)
+# FIXME

crates/ruff/resources/test/fixtures/flake8_todos/TD006.py

@@ -0,0 +1,5 @@
+# TDO006 - accepted
+# TODO (evanrittenhouse): this is a valid TODO
+# TDO006 - error
+# ToDo (evanrittenhouse): invalid capitalization
+# todo (evanrittenhouse): another invalid capitalization

crates/ruff/resources/test/fixtures/flake8_todos/TD007.py

@@ -0,0 +1,8 @@
+# T007 - accepted
+# TODO(evanrittenhouse): this has a space after a colon
+# TODO: so does this
+# T007 - errors
+# TODO(evanrittenhouse):this has no space after a colon
+# TODO (evanrittenhouse):this doesn't either
+# TODO:neither does this
+# FIXME:and lastly neither does this

crates/ruff/src/checkers/tokens.rs

@@ -7,8 +7,8 @@ use crate::lex::docstring_detection::StateMachine;
 use crate::registry::{AsRule, Rule};
 use crate::rules::ruff::rules::Context;
 use crate::rules::{
-    eradicate, flake8_commas, flake8_implicit_str_concat, flake8_pyi, flake8_quotes, pycodestyle,
+    eradicate, flake8_commas, flake8_implicit_str_concat, flake8_pyi, flake8_quotes, flake8_todos,
-    pylint, pyupgrade, ruff,
+    pycodestyle, pylint, pyupgrade, ruff,
 };
 use crate::settings::Settings;
 use ruff_diagnostics::Diagnostic;
@@ -59,6 +59,15 @@ pub(crate) fn check_tokens(
     ]);
     let enforce_extraneous_parenthesis = settings.rules.enabled(Rule::ExtraneousParentheses);
     let enforce_type_comment_in_stub = settings.rules.enabled(Rule::TypeCommentInStub);
+    let enforce_todos = settings.rules.any_enabled(&[
+        Rule::InvalidTodoTag,
+        Rule::MissingTodoAuthor,
+        Rule::MissingTodoLink,
+        Rule::MissingTodoColon,
+        Rule::MissingTodoDescription,
+        Rule::InvalidTodoCapitalization,
+        Rule::MissingSpaceAfterTodoColon,
+    ]);
 
     // RUF001, RUF002, RUF003
     if enforce_ambiguous_unicode_character {
@@ -179,5 +188,14 @@ pub(crate) fn check_tokens(
         diagnostics.extend(flake8_pyi::rules::type_comment_in_stub(tokens));
     }
 
+    // TD001, TD002, TD003, TD004, TD005, TD006, TD007
+    if enforce_todos {
+        diagnostics.extend(
+            flake8_todos::rules::todos(tokens, settings)
+                .into_iter()
+                .filter(|diagnostic| settings.rules.enabled(diagnostic.kind.rule())),
+        );
+    }
+
     diagnostics
 }

crates/ruff/src/codes.rs

@@ -743,6 +743,14 @@ pub fn code_to_rule(linter: Linter, code: &str) -> Option<Rule> {
         // Reserved: (Flynt, "001") => Rule::StringConcatenationToFString,
         (Flynt, "002") => Rule::StaticJoinToFString,
 
+        // flake8-todo
+        (Flake8Todo, "001") => Rule::InvalidTodoTag,
+        (Flake8Todo, "002") => Rule::MissingTodoAuthor,
+        (Flake8Todo, "003") => Rule::MissingTodoLink,
+        (Flake8Todo, "004") => Rule::MissingTodoColon,
+        (Flake8Todo, "005") => Rule::MissingTodoDescription,
+        (Flake8Todo, "006") => Rule::InvalidTodoCapitalization,
+        (Flake8Todo, "007") => Rule::MissingSpaceAfterTodoColon,
         _ => return None,
     })
 }

crates/ruff/src/registry.rs

@@ -674,6 +674,14 @@ ruff_macros::register_rules!(
     rules::flake8_django::rules::DjangoNonLeadingReceiverDecorator,
     // flynt
     rules::flynt::rules::StaticJoinToFString,
+    // flake8-todo
+    rules::flake8_todos::rules::InvalidTodoTag,
+    rules::flake8_todos::rules::MissingTodoAuthor,
+    rules::flake8_todos::rules::MissingTodoLink,
+    rules::flake8_todos::rules::MissingTodoColon,
+    rules::flake8_todos::rules::MissingTodoDescription,
+    rules::flake8_todos::rules::InvalidTodoCapitalization,
+    rules::flake8_todos::rules::MissingSpaceAfterTodoColon,
 );
 
 pub trait AsRule {
@@ -814,6 +822,9 @@ pub enum Linter {
     /// [flake8-use-pathlib](https://pypi.org/project/flake8-use-pathlib/)
     #[prefix = "PTH"]
     Flake8UsePathlib,
+    /// [flake8-todos](https://github.com/orsinium-labs/flake8-todos/)
+    #[prefix = "TD"]
+    Flake8Todo,
     /// [eradicate](https://pypi.org/project/eradicate/)
     #[prefix = "ERA"]
     Eradicate,
@@ -938,7 +949,14 @@ impl Rule {
             | Rule::UselessSemicolon
             | Rule::MultipleStatementsOnOneLineSemicolon
             | Rule::ProhibitedTrailingComma
-            | Rule::TypeCommentInStub => LintSource::Tokens,
+            | Rule::TypeCommentInStub
+            | Rule::InvalidTodoTag
+            | Rule::MissingTodoAuthor
+            | Rule::MissingTodoLink
+            | Rule::MissingTodoColon
+            | Rule::MissingTodoDescription
+            | Rule::InvalidTodoCapitalization
+            | Rule::MissingSpaceAfterTodoColon => LintSource::Tokens,
             Rule::IOError => LintSource::Io,
             Rule::UnsortedImports | Rule::MissingRequiredImport => LintSource::Imports,
             Rule::ImplicitNamespacePackage | Rule::InvalidModuleName => LintSource::Filesystem,

crates/ruff/src/rules/flake8_todos/mod.rs

@@ -0,0 +1,31 @@
+pub(crate) mod rules;
+
+#[cfg(test)]
+mod tests {
+    use std::convert::AsRef;
+    use std::path::Path;
+
+    use anyhow::Result;
+    use test_case::test_case;
+
+    use crate::registry::Rule;
+    use crate::test::test_path;
+    use crate::{assert_messages, settings};
+
+    #[test_case(Rule::InvalidTodoTag, Path::new("TD001.py"); "TD001")]
+    #[test_case(Rule::MissingTodoAuthor, Path::new("TD002.py"); "TD002")]
+    #[test_case(Rule::MissingTodoLink, Path::new("TD003.py"); "TD003")]
+    #[test_case(Rule::MissingTodoColon, Path::new("TD004.py"); "TD004")]
+    #[test_case(Rule::MissingTodoDescription, Path::new("TD005.py"); "TD005")]
+    #[test_case(Rule::InvalidTodoCapitalization, Path::new("TD006.py"); "TD006")]
+    #[test_case(Rule::MissingSpaceAfterTodoColon, Path::new("TD007.py"); "TD007")]
+    fn rules(rule_code: Rule, path: &Path) -> Result<()> {
+        let snapshot = format!("{}_{}", rule_code.as_ref(), path.to_string_lossy());
+        let diagnostics = test_path(
+            Path::new("flake8_todos").join(path).as_path(),
+            &settings::Settings::for_rule(rule_code),
+        )?;
+        assert_messages!(snapshot, diagnostics);
+        Ok(())
+    }
+}

crates/ruff/src/rules/flake8_todos/rules.rs

@@ -0,0 +1,458 @@
+use itertools::Itertools;
+use once_cell::sync::Lazy;
+use regex::RegexSet;
+use ruff_text_size::{TextLen, TextRange, TextSize};
+use rustpython_parser::lexer::LexResult;
+use rustpython_parser::Tok;
+
+use ruff_diagnostics::{AlwaysAutofixableViolation, Diagnostic, Edit, Fix, Violation};
+use ruff_macros::{derive_message_formats, violation};
+
+use crate::{registry::Rule, settings::Settings};
+
+/// ## What it does
+/// Checks that a TODO comment is labelled with "TODO".
+///
+/// ## Why is this bad?
+/// Ambiguous tags reduce code visibility and can lead to dangling TODOs.
+/// For example, if a comment is tagged with "FIXME" rather than "TODO", it may
+/// be overlooked by future readers.
+///
+/// Note that this rule will only flag "FIXME" and "XXX" tags as incorrect.
+///
+/// ## Example
+/// ```python
+/// # FIXME(ruff): this should get fixed!
+/// ```
+///
+/// Use instead:
+/// ```python
+/// # TODO(ruff): this is now fixed!
+/// ```
+#[violation]
+pub struct InvalidTodoTag {
+    pub tag: String,
+}
+
+impl Violation for InvalidTodoTag {
+    #[derive_message_formats]
+    fn message(&self) -> String {
+        let InvalidTodoTag { tag } = self;
+        format!("Invalid TODO tag: `{tag}`")
+    }
+}
+
+/// ## What it does
+/// Checks that a TODO comment includes an author.
+///
+/// ## Why is this bad?
+/// Including an author on a TODO provides future readers with context around
+/// the issue. While the TODO author is not always considered responsible for
+/// fixing the issue, they are typically the individual with the most context.
+///
+/// ## Example
+/// ```python
+/// # TODO: should assign an author here
+/// ```
+///
+/// Use instead
+/// ```python
+/// # TODO(charlie): now an author is assigned
+/// ```
+#[violation]
+pub struct MissingTodoAuthor;
+
+impl Violation for MissingTodoAuthor {
+    #[derive_message_formats]
+    fn message(&self) -> String {
+        format!("Missing author in TODO; try: `# TODO(<author_name>): ...`")
+    }
+}
+
+/// ## What it does
+/// Checks that a TODO comment is associated with a link to a relevant issue
+/// or ticket.
+///
+/// ## Why is this bad?
+/// Including an issue link near a TODO makes it easier for resolvers
+/// to get context around the issue.
+///
+/// ## Example
+/// ```python
+/// # TODO: this link has no issue
+/// ```
+///
+/// Use one of these instead:
+/// ```python
+/// # TODO(charlie): this comment has an issue link
+/// # https://github.com/charliermarsh/ruff/issues/3870
+///
+/// # TODO(charlie): this comment has a 3-digit issue code
+/// # 003
+///
+/// # TODO(charlie): this comment has an issue code of (up to) 6 characters, then digits
+/// # SIXCHR-003
+/// ```
+#[violation]
+pub struct MissingTodoLink;
+
+impl Violation for MissingTodoLink {
+    #[derive_message_formats]
+    fn message(&self) -> String {
+        format!("Missing issue link on the line following this TODO")
+    }
+}
+
+/// ## What it does
+/// Checks that a "TODO" tag is followed by a colon.
+///
+/// ## Why is this bad?
+/// "TODO" tags are typically followed by a parenthesized author name, a colon,
+/// a space, and a description of the issue, in that order.
+///
+/// Deviating from this pattern can lead to inconsistent and non-idiomatic
+/// comments.
+///
+/// ## Example
+/// ```python
+/// # TODO(charlie) fix this colon
+/// ```
+///
+/// Used instead:
+/// ```python
+/// # TODO(charlie): colon fixed
+/// ```
+#[violation]
+pub struct MissingTodoColon;
+
+impl Violation for MissingTodoColon {
+    #[derive_message_formats]
+    fn message(&self) -> String {
+        format!("Missing colon in TODO")
+    }
+}
+
+/// ## What it does
+/// Checks that a "TODO" tag contains a description of the issue following the
+/// tag itself.
+///
+/// ## Why is this bad?
+/// TODO comments should include a description of the issue to provide context
+/// for future readers.
+///
+/// ## Example
+/// ```python
+/// # TODO(charlie)
+/// ```
+///
+/// Use instead:
+/// ```python
+/// # TODO(charlie): fix some issue
+/// ```
+#[violation]
+pub struct MissingTodoDescription;
+
+impl Violation for MissingTodoDescription {
+    #[derive_message_formats]
+    fn message(&self) -> String {
+        format!("Missing issue description after `TODO`")
+    }
+}
+
+/// ## What it does
+/// Checks that a "TODO" tag is properly capitalized (i.e., that the tag is
+/// uppercase).
+///
+/// ## Why is this bad?
+/// Capitalizing the "TODO" in a TODO comment is a convention that makes it
+/// easier for future readers to identify TODOs.
+///
+/// ## Example
+/// ```python
+/// # todo(charlie): capitalize this
+/// ```
+///
+/// Use instead:
+/// ```python
+/// # TODO(charlie): this is capitalized
+/// ```
+#[violation]
+pub struct InvalidTodoCapitalization {
+    tag: String,
+}
+
+impl AlwaysAutofixableViolation for InvalidTodoCapitalization {
+    #[derive_message_formats]
+    fn message(&self) -> String {
+        let InvalidTodoCapitalization { tag } = self;
+        format!("Invalid TODO capitalization: `{tag}` should be `TODO`")
+    }
+
+    fn autofix_title(&self) -> String {
+        let InvalidTodoCapitalization { tag } = self;
+        format!("Replace `{tag}` with `TODO`")
+    }
+}
+
+/// ## What it does
+/// Checks that the colon after a "TODO" tag is followed by a space.
+///
+/// ## Why is this bad?
+/// "TODO" tags are typically followed by a parenthesized author name, a colon,
+/// a space, and a description of the issue, in that order.
+///
+/// Deviating from this pattern can lead to inconsistent and non-idiomatic
+/// comments.
+///
+/// ## Example
+/// ```python
+/// # TODO(charlie):fix this
+/// ```
+///
+/// Use instead:
+/// ```python
+/// # TODO(charlie): fix this
+/// ```
+#[violation]
+pub struct MissingSpaceAfterTodoColon;
+
+impl Violation for MissingSpaceAfterTodoColon {
+    #[derive_message_formats]
+    fn message(&self) -> String {
+        format!("Missing space after colon in TODO")
+    }
+}
+
+static TODO_REGEX_SET: Lazy<RegexSet> = Lazy::new(|| {
+    RegexSet::new([
+        r#"^#\s*(?i)(TODO).*$"#,
+        r#"^#\s*(?i)(FIXME).*$"#,
+        r#"^#\s*(?i)(XXX).*$"#,
+    ])
+    .unwrap()
+});
+
+// Maps the index of a particular Regex (specified by its index in the above TODO_REGEX_SET slice)
+// to the length of the tag that we're trying to capture.
+static PATTERN_TAG_LENGTH: &[usize; 3] = &["TODO".len(), "FIXME".len(), "XXX".len()];
+
+static ISSUE_LINK_REGEX_SET: Lazy<RegexSet> = Lazy::new(|| {
+    let patterns: [&str; 3] = [
+        r#"^#\s*(http|https)://.*"#, // issue link
+        r#"^#\s*\d+$"#,              // issue code - like "003"
+        r#"^#\s*[A-Z]{1,6}\-?\d+$"#, // issue code - like "TD003" or "TD-003"
+    ];
+    RegexSet::new(patterns).unwrap()
+});
+
+// If this struct ever gets pushed outside of this module, it may be worth creating an enum for
+// the different tag types + other convenience methods.
+/// Represents a TODO tag or any of its variants - FIXME, XXX, TODO.
+#[derive(Debug, PartialEq, Eq)]
+struct Tag<'a> {
+    range: TextRange,
+    content: &'a str,
+}
+
+pub(crate) fn todos(tokens: &[LexResult], settings: &Settings) -> Vec<Diagnostic> {
+    let mut diagnostics: Vec<Diagnostic> = vec![];
+
+    let mut iter = tokens.iter().flatten().multipeek();
+    while let Some((token, token_range)) = iter.next() {
+        let Tok::Comment(comment) = token else {
+            continue;
+        };
+
+        // Check that the comment is a TODO (properly formed or not).
+        let Some(tag) = detect_tag(comment, token_range) else {
+            continue;
+        };
+
+        tag_errors(&tag, &mut diagnostics, settings);
+        static_errors(&mut diagnostics, comment, *token_range, &tag);
+
+        // TD003
+        let mut has_issue_link = false;
+        while let Some((token, token_range)) = iter.peek() {
+            if let Tok::Comment(comment) = token {
+                if detect_tag(comment, token_range).is_some() {
+                    break;
+                }
+                if ISSUE_LINK_REGEX_SET.is_match(comment) {
+                    has_issue_link = true;
+                    break;
+                }
+            } else {
+                break;
+            }
+        }
+        if !has_issue_link {
+            diagnostics.push(Diagnostic::new(MissingTodoLink, tag.range));
+        }
+    }
+
+    diagnostics
+}
+
+/// Returns the tag pulled out of a given comment, if it exists.
+fn detect_tag<'a>(comment: &'a str, comment_range: &'a TextRange) -> Option<Tag<'a>> {
+    let Some(regex_index) = TODO_REGEX_SET.matches(comment).into_iter().next() else {
+        return None;
+    };
+
+    let tag_length = PATTERN_TAG_LENGTH[regex_index];
+
+    let mut tag_start_offset = 0usize;
+    for (i, char) in comment.chars().enumerate() {
+        // Regex ensures that the first letter in the comment is the first letter of the tag.
+        if char.is_alphabetic() {
+            tag_start_offset = i;
+            break;
+        }
+    }
+
+    Some(Tag {
+        content: &comment[tag_start_offset..tag_start_offset + tag_length],
+        range: TextRange::at(
+            comment_range.start() + TextSize::try_from(tag_start_offset).ok().unwrap(),
+            TextSize::try_from(tag_length).ok().unwrap(),
+        ),
+    })
+}
+
+/// Check that the tag itself is valid. This function modifies `diagnostics` in-place.
+fn tag_errors(tag: &Tag, diagnostics: &mut Vec<Diagnostic>, settings: &Settings) {
+    if tag.content == "TODO" {
+        return;
+    }
+
+    if tag.content.to_uppercase() == "TODO" {
+        // TD006
+        let mut diagnostic = Diagnostic::new(
+            InvalidTodoCapitalization {
+                tag: tag.content.to_string(),
+            },
+            tag.range,
+        );
+
+        if settings.rules.should_fix(Rule::InvalidTodoCapitalization) {
+            diagnostic.set_fix(Fix::automatic(Edit::range_replacement(
+                "TODO".to_string(),
+                tag.range,
+            )));
+        }
+
+        diagnostics.push(diagnostic);
+    } else {
+        // TD001
+        diagnostics.push(Diagnostic::new(
+            InvalidTodoTag {
+                tag: tag.content.to_string(),
+            },
+            tag.range,
+        ));
+    }
+}
+
+/// Checks for "static" errors in the comment: missing colon, missing author, etc. This function
+/// modifies `diagnostics` in-place.
+fn static_errors(
+    diagnostics: &mut Vec<Diagnostic>,
+    comment: &str,
+    comment_range: TextRange,
+    tag: &Tag,
+) {
+    let post_tag = &comment[usize::from(tag.range.end() - comment_range.start())..];
+    let trimmed = post_tag.trim_start();
+    let content_offset = post_tag.text_len() - trimmed.text_len();
+
+    let author_end = content_offset
+        + if trimmed.starts_with('(') {
+            if let Some(end_index) = trimmed.find(')') {
+                TextSize::try_from(end_index + 1).unwrap()
+            } else {
+                trimmed.text_len()
+            }
+        } else {
+            diagnostics.push(Diagnostic::new(MissingTodoAuthor, tag.range));
+
+            TextSize::new(0)
+        };
+
+    let post_author = &post_tag[usize::from(author_end)..];
+
+    let post_colon = if let Some((.., after_colon)) = post_author.split_once(':') {
+        if let Some(stripped) = after_colon.strip_prefix(' ') {
+            stripped
+        } else {
+            diagnostics.push(Diagnostic::new(MissingSpaceAfterTodoColon, tag.range));
+            after_colon
+        }
+    } else {
+        diagnostics.push(Diagnostic::new(MissingTodoColon, tag.range));
+        ""
+    };
+
+    if post_colon.is_empty() {
+        diagnostics.push(Diagnostic::new(MissingTodoDescription, tag.range));
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_detect_tag() {
+        let test_comment = "# TODO: todo tag";
+        let expected = Tag {
+            content: "TODO",
+            range: TextRange::new(TextSize::new(2), TextSize::new(6)),
+        };
+        assert_eq!(
+            Some(expected),
+            detect_tag(
+                test_comment,
+                &TextRange::new(TextSize::new(0), TextSize::new(15)),
+            )
+        );
+
+        let test_comment = "#TODO: todo tag";
+        let expected = Tag {
+            content: "TODO",
+            range: TextRange::new(TextSize::new(1), TextSize::new(5)),
+        };
+        assert_eq!(
+            Some(expected),
+            detect_tag(
+                test_comment,
+                &TextRange::new(TextSize::new(0), TextSize::new(15)),
+            )
+        );
+
+        let test_comment = "# todo: todo tag";
+        let expected = Tag {
+            content: "todo",
+            range: TextRange::new(TextSize::new(2), TextSize::new(6)),
+        };
+        assert_eq!(
+            Some(expected),
+            detect_tag(
+                test_comment,
+                &TextRange::new(TextSize::new(0), TextSize::new(15)),
+            )
+        );
+        let test_comment = "# fixme: fixme tag";
+        let expected = Tag {
+            content: "fixme",
+            range: TextRange::new(TextSize::new(2), TextSize::new(7)),
+        };
+        assert_eq!(
+            Some(expected),
+            detect_tag(
+                test_comment,
+                &TextRange::new(TextSize::new(0), TextSize::new(17)),
+            )
+        );
+    }
+}

crates/ruff/src/rules/flake8_todos/snapshots/ruff__rules__flake8_todos__tests__invalid-todo-capitalization_TD006.py.snap

@@ -0,0 +1,38 @@
+---
+source: crates/ruff/src/rules/flake8_todos/mod.rs
+---
+TD006.py:4:3: TD006 [*] Invalid TODO capitalization: `ToDo` should be `TODO`
+  |
+4 | # TODO (evanrittenhouse): this is a valid TODO
+5 | # TDO006 - error
+6 | # ToDo (evanrittenhouse): invalid capitalization
+  |   ^^^^ TD006
+7 | # todo (evanrittenhouse): another invalid capitalization
+  |
+  = help: Replace `ToDo` with `TODO`
+
+ℹ Fix
+1 1 | # TDO006 - accepted
+2 2 | # TODO (evanrittenhouse): this is a valid TODO
+3 3 | # TDO006 - error
+4   |-# ToDo (evanrittenhouse): invalid capitalization
+  4 |+# TODO (evanrittenhouse): invalid capitalization
+5 5 | # todo (evanrittenhouse): another invalid capitalization
+
+TD006.py:5:3: TD006 [*] Invalid TODO capitalization: `todo` should be `TODO`
+  |
+5 | # TDO006 - error
+6 | # ToDo (evanrittenhouse): invalid capitalization
+7 | # todo (evanrittenhouse): another invalid capitalization
+  |   ^^^^ TD006
+  |
+  = help: Replace `todo` with `TODO`
+
+ℹ Fix
+2 2 | # TODO (evanrittenhouse): this is a valid TODO
+3 3 | # TDO006 - error
+4 4 | # ToDo (evanrittenhouse): invalid capitalization
+5   |-# todo (evanrittenhouse): another invalid capitalization
+  5 |+# TODO (evanrittenhouse): another invalid capitalization
+
+

crates/ruff/src/rules/flake8_todos/snapshots/ruff__rules__flake8_todos__tests__invalid-todo-tag_TD001.py.snap

@@ -0,0 +1,20 @@
+---
+source: crates/ruff/src/rules/flake8_todos/mod.rs
+---
+TD001.py:7:3: TD001 Invalid TODO tag: `XXX`
+  |
+7 | # T001 - errors
+8 | # XXX (evanrittenhouse): this is not fine
+  |   ^^^ TD001
+9 | # FIXME (evanrittenhouse): this is not fine
+  |
+
+TD001.py:8:3: TD001 Invalid TODO tag: `FIXME`
+   |
+ 8 | # T001 - errors
+ 9 | # XXX (evanrittenhouse): this is not fine
+10 | # FIXME (evanrittenhouse): this is not fine
+   |   ^^^^^ TD001
+   |
+
+

crates/ruff/src/rules/flake8_todos/snapshots/ruff__rules__flake8_todos__tests__missing-space-after-todo-colon_TD007.py.snap

@@ -0,0 +1,41 @@
+---
+source: crates/ruff/src/rules/flake8_todos/mod.rs
+---
+TD007.py:5:3: TD007 Missing space after colon in TODO
+  |
+5 | # TODO: so does this
+6 | # T007 - errors
+7 | # TODO(evanrittenhouse):this has no space after a colon
+  |   ^^^^ TD007
+8 | # TODO (evanrittenhouse):this doesn't either
+9 | # TODO:neither does this
+  |
+
+TD007.py:6:3: TD007 Missing space after colon in TODO
+   |
+ 6 | # T007 - errors
+ 7 | # TODO(evanrittenhouse):this has no space after a colon
+ 8 | # TODO (evanrittenhouse):this doesn't either
+   |   ^^^^ TD007
+ 9 | # TODO:neither does this
+10 | # FIXME:and lastly neither does this
+   |
+
+TD007.py:7:3: TD007 Missing space after colon in TODO
+   |
+ 7 | # TODO(evanrittenhouse):this has no space after a colon
+ 8 | # TODO (evanrittenhouse):this doesn't either
+ 9 | # TODO:neither does this
+   |   ^^^^ TD007
+10 | # FIXME:and lastly neither does this
+   |
+
+TD007.py:8:3: TD007 Missing space after colon in TODO
+   |
+ 8 | # TODO (evanrittenhouse):this doesn't either
+ 9 | # TODO:neither does this
+10 | # FIXME:and lastly neither does this
+   |   ^^^^^ TD007
+   |
+
+

crates/ruff/src/rules/flake8_todos/snapshots/ruff__rules__flake8_todos__tests__missing-todo-author_TD002.py.snap

@@ -0,0 +1,31 @@
+---
+source: crates/ruff/src/rules/flake8_todos/mod.rs
+---
+TD002.py:5:3: TD002 Missing author in TODO; try: `# TODO(<author_name>): ...`
+  |
+5 | # TODO(evanrittenhouse): this also has an author
+6 | # T002 - errors
+7 | # TODO: this has no author
+  |   ^^^^ TD002
+8 | # FIXME: neither does this
+9 | # TODO : and neither does this
+  |
+
+TD002.py:6:3: TD002 Missing author in TODO; try: `# TODO(<author_name>): ...`
+  |
+6 | # T002 - errors
+7 | # TODO: this has no author
+8 | # FIXME: neither does this
+  |   ^^^^^ TD002
+9 | # TODO : and neither does this
+  |
+
+TD002.py:7:3: TD002 Missing author in TODO; try: `# TODO(<author_name>): ...`
+  |
+7 | # TODO: this has no author
+8 | # FIXME: neither does this
+9 | # TODO : and neither does this
+  |   ^^^^ TD002
+  |
+
+

crates/ruff/src/rules/flake8_todos/snapshots/ruff__rules__flake8_todos__tests__missing-todo-colon_TD004.py.snap

@@ -0,0 +1,31 @@
+---
+source: crates/ruff/src/rules/flake8_todos/mod.rs
+---
+TD004.py:4:3: TD004 Missing colon in TODO
+  |
+4 | # TODO(evanrittenhouse): this has a colon
+5 | # T004 - errors
+6 | # TODO this has no colon
+  |   ^^^^ TD004
+7 | # TODO(evanrittenhouse 😀) this has no colon
+8 | # FIXME add a colon
+  |
+
+TD004.py:5:3: TD004 Missing colon in TODO
+  |
+5 | # T004 - errors
+6 | # TODO this has no colon
+7 | # TODO(evanrittenhouse 😀) this has no colon
+  |   ^^^^ TD004
+8 | # FIXME add a colon
+  |
+
+TD004.py:6:3: TD004 Missing colon in TODO
+  |
+6 | # TODO this has no colon
+7 | # TODO(evanrittenhouse 😀) this has no colon
+8 | # FIXME add a colon
+  |   ^^^^^ TD004
+  |
+
+

crates/ruff/src/rules/flake8_todos/snapshots/ruff__rules__flake8_todos__tests__missing-todo-description_TD005.py.snap

@@ -0,0 +1,31 @@
+---
+source: crates/ruff/src/rules/flake8_todos/mod.rs
+---
+TD005.py:4:3: TD005 Missing issue description after `TODO`
+  |
+4 | # TODO(evanrittenhouse): this has text, while the errors do not
+5 | # T005 - errors
+6 | # TODO(evanrittenhouse):
+  |   ^^^^ TD005
+7 | # TODO(evanrittenhouse)
+8 | # FIXME
+  |
+
+TD005.py:5:3: TD005 Missing issue description after `TODO`
+  |
+5 | # T005 - errors
+6 | # TODO(evanrittenhouse):
+7 | # TODO(evanrittenhouse)
+  |   ^^^^ TD005
+8 | # FIXME
+  |
+
+TD005.py:6:3: TD005 Missing issue description after `TODO`
+  |
+6 | # TODO(evanrittenhouse):
+7 | # TODO(evanrittenhouse)
+8 | # FIXME
+  |   ^^^^^ TD005
+  |
+
+

crates/ruff/src/rules/flake8_todos/snapshots/ruff__rules__flake8_todos__tests__missing-todo-link_TD003.py.snap

@@ -0,0 +1,40 @@
+---
+source: crates/ruff/src/rules/flake8_todos/mod.rs
+---
+TD003.py:9:3: TD003 Missing issue link on the line following this TODO
+   |
+ 9 | # TDO003 - errors
+10 | # TODO: this comment has no
+   |   ^^^^ TD003
+11 | # link after it
+   |
+
+TD003.py:12:3: TD003 Missing issue link on the line following this TODO
+   |
+12 | # link after it
+13 | 
+14 | # TODO: here's a TODO with no link after it
+   |   ^^^^ TD003
+15 | def foo(x):
+16 |     return x
+   |
+
+TD003.py:25:3: TD003 Missing issue link on the line following this TODO
+   |
+25 | # TDO-3870
+26 | 
+27 | # TODO: here's a TODO without an issue link
+   |   ^^^^ TD003
+28 | # TODO: followed by a new TODO with an issue link
+29 | # TDO-3870
+   |
+
+TD003.py:29:3: TD003 Missing issue link on the line following this TODO
+   |
+29 | # TDO-3870
+30 | 
+31 | # TODO: here's a TODO on the last line with no link
+   |   ^^^^ TD003
+   |
+
+

crates/ruff/src/rules/mod.rs

@@ -29,6 +29,7 @@ pub mod flake8_return;
 pub mod flake8_self;
 pub mod flake8_simplify;
 pub mod flake8_tidy_imports;
+pub mod flake8_todos;
 pub mod flake8_type_checking;
 pub mod flake8_unused_arguments;
 pub mod flake8_use_pathlib;

docs/faq.md

@@ -63,6 +63,7 @@ natively, including:
 - [flake8-simplify](https://pypi.org/project/flake8-simplify/)
 - [flake8-super](https://pypi.org/project/flake8-super/)
 - [flake8-tidy-imports](https://pypi.org/project/flake8-tidy-imports/)
+- [flake8-todos](https://pypi.org/project/flake8-todos/)
 - [flake8-type-checking](https://pypi.org/project/flake8-type-checking/)
 - [flake8-use-pathlib](https://pypi.org/project/flake8-use-pathlib/)
 - [flynt](https://pypi.org/project/flynt/) ([#2102](https://github.com/charliermarsh/ruff/issues/2102))
@@ -161,6 +162,7 @@ Today, Ruff can be used to replace Flake8 when used with any of the following pl
 - [flake8-simplify](https://pypi.org/project/flake8-simplify/)
 - [flake8-super](https://pypi.org/project/flake8-super/)
 - [flake8-tidy-imports](https://pypi.org/project/flake8-tidy-imports/)
+- [flake8-todos](https://pypi.org/project/flake8-todos/)
 - [flake8-type-checking](https://pypi.org/project/flake8-type-checking/)
 - [flake8-use-pathlib](https://pypi.org/project/flake8-use-pathlib/)
 - [flynt](https://pypi.org/project/flynt/) ([#2102](https://github.com/charliermarsh/ruff/issues/2102))

ruff.schema.json

@@ -2296,6 +2296,16 @@
         "TCH003",
         "TCH004",
         "TCH005",
+        "TD",
+        "TD0",
+        "TD00",
+        "TD001",
+        "TD002",
+        "TD003",
+        "TD004",
+        "TD005",
+        "TD006",
+        "TD007",
         "TID",
         "TID2",
         "TID25",