Allow flagging of multiline implicit string concatenations (#2117)

At present, `ISC001` and `ISC002` flag concatenations like the following:

```py
"a" "b"  # ISC001
"a" \
  "b"  # ISC002
```

However, multiline concatenations are allowed.

This PR adds a setting:

```toml
[tool.ruff.flake8-implicit-str-concat]
allow-multiline = false
```

Which extends `ISC002` to _also_ flag multiline concatenations, like:

```py
(
  "a"  # ISC002
  "b"
)
```

Note that this is backwards compatible, as `allow-multiline` defaults to `true`.

README.md

@@ -2684,6 +2684,28 @@ max-string-length = 20
 
 ---
 
+### `flake8-implicit-str-concat`
+
+#### [`allow-multiline`](#allow-multiline)
+
+Whether to allow implicit string concatenations for multiline strings.
+By default, implicit concatenations of multiline strings are
+allowed (but continuation lines, delimited with a backslash, are
+prohibited).
+
+**Default value**: `true`
+
+**Type**: `bool`
+
+**Example usage**:
+
+```toml
+[tool.ruff.flake8-implicit-str-concat]
+allow-multiline = false
+```
+
+---
+
 ### `flake8-import-conventions`
 
 #### [`aliases`](#aliases)

ruff.schema.json

@@ -175,6 +175,17 @@
         }
       ]
     },
+    "flake8-implicit-str-concat": {
+      "description": "Options for the `flake8-implicit-str-concat` plugin.",
+      "anyOf": [
+        {
+          "$ref": "#/definitions/Flake8ImplicitStrConcatOptions"
+        },
+        {
+          "type": "null"
+        }
+      ]
+    },
     "flake8-import-conventions": {
       "description": "Options for the `flake8-import-conventions` plugin.",
       "anyOf": [
@@ -626,6 +637,19 @@
       },
       "additionalProperties": false
     },
+    "Flake8ImplicitStrConcatOptions": {
+      "type": "object",
+      "properties": {
+        "allow-multiline": {
+          "description": "Whether to allow implicit string concatenations for multiline strings. By default, implicit concatenations of multiline strings are allowed (but continuation lines, delimited with a backslash, are prohibited).",
+          "type": [
+            "boolean",
+            "null"
+          ]
+        }
+      },
+      "additionalProperties": false
+    },
     "Flake8ImportConventionsOptions": {
       "type": "object",
       "properties": {

src/checkers/tokens.rs

@@ -124,9 +124,12 @@ pub fn check_tokens(
     // ISC001, ISC002
     if enforce_implicit_string_concatenation {
         diagnostics.extend(
-            flake8_implicit_str_concat::rules::implicit(tokens)
+            flake8_implicit_str_concat::rules::implicit(
-                .into_iter()
+                tokens,
-                .filter(|diagnostic| settings.rules.enabled(diagnostic.kind.rule())),
+                &settings.flake8_implicit_str_concat,
+            )
+            .into_iter()
+            .filter(|diagnostic| settings.rules.enabled(diagnostic.kind.rule())),
         );
     }
 

src/flake8_to_ruff/converter.rs

@@ -467,6 +467,7 @@ mod tests {
             flake8_pytest_style: None,
             flake8_quotes: None,
             flake8_tidy_imports: None,
+            flake8_implicit_str_concat: None,
             flake8_import_conventions: None,
             flake8_unused_arguments: None,
             isort: None,
@@ -531,6 +532,7 @@ mod tests {
             flake8_pytest_style: None,
             flake8_quotes: None,
             flake8_tidy_imports: None,
+            flake8_implicit_str_concat: None,
             flake8_import_conventions: None,
             flake8_unused_arguments: None,
             isort: None,
@@ -595,6 +597,7 @@ mod tests {
             flake8_pytest_style: None,
             flake8_quotes: None,
             flake8_tidy_imports: None,
+            flake8_implicit_str_concat: None,
             flake8_import_conventions: None,
             flake8_unused_arguments: None,
             isort: None,
@@ -659,6 +662,7 @@ mod tests {
             flake8_pytest_style: None,
             flake8_quotes: None,
             flake8_tidy_imports: None,
+            flake8_implicit_str_concat: None,
             flake8_import_conventions: None,
             flake8_unused_arguments: None,
             isort: None,
@@ -728,6 +732,7 @@ mod tests {
                 avoid_escape: None,
             }),
             flake8_tidy_imports: None,
+            flake8_implicit_str_concat: None,
             flake8_import_conventions: None,
             flake8_unused_arguments: None,
             isort: None,
@@ -800,6 +805,7 @@ mod tests {
             flake8_pytest_style: None,
             flake8_quotes: None,
             flake8_tidy_imports: None,
+            flake8_implicit_str_concat: None,
             flake8_import_conventions: None,
             flake8_unused_arguments: None,
             isort: None,
@@ -876,6 +882,7 @@ mod tests {
                 avoid_escape: None,
             }),
             flake8_tidy_imports: None,
+            flake8_implicit_str_concat: None,
             flake8_import_conventions: None,
             flake8_unused_arguments: None,
             isort: None,

src/lib_wasm.rs

@@ -10,9 +10,9 @@ use crate::linter::check_path;
 use crate::registry::Rule;
 use crate::rules::{
     flake8_annotations, flake8_bandit, flake8_bugbear, flake8_builtins, flake8_errmsg,
-    flake8_import_conventions, flake8_pytest_style, flake8_quotes, flake8_tidy_imports,
+    flake8_implicit_str_concat, flake8_import_conventions, flake8_pytest_style, flake8_quotes,
-    flake8_unused_arguments, isort, mccabe, pep8_naming, pycodestyle, pydocstyle, pylint,
+    flake8_tidy_imports, flake8_unused_arguments, isort, mccabe, pep8_naming, pycodestyle,
-    pyupgrade,
+    pydocstyle, pylint, pyupgrade,
 };
 use crate::rustpython_helpers::tokenize;
 use crate::settings::configuration::Configuration;
@@ -142,6 +142,9 @@ pub fn defaultSettings() -> Result<JsValue, JsValue> {
         flake8_pytest_style: Some(flake8_pytest_style::settings::Settings::default().into()),
         flake8_quotes: Some(flake8_quotes::settings::Settings::default().into()),
         flake8_tidy_imports: Some(flake8_tidy_imports::Settings::default().into()),
+        flake8_implicit_str_concat: Some(
+            flake8_implicit_str_concat::settings::Settings::default().into(),
+        ),
         flake8_import_conventions: Some(
             flake8_import_conventions::settings::Settings::default().into(),
         ),

src/registry.rs

@@ -656,9 +656,9 @@ impl Rule {
             | Rule::BadQuotesInlineString
             | Rule::BadQuotesMultilineString
             | Rule::CommentedOutCode
+            | Rule::MultiLineImplicitStringConcatenation
             | Rule::ExtraneousParentheses
             | Rule::InvalidEscapeSequence
-            | Rule::MultiLineImplicitStringConcatenation
             | Rule::SingleLineImplicitStringConcatenation
             | Rule::TrailingCommaMissing
             | Rule::TrailingCommaOnBareTupleProhibited

src/rules/flake8_implicit_str_concat/mod.rs

@@ -1,5 +1,6 @@
 //! Rules from [flake8-implicit-str-concat](https://pypi.org/project/flake8-implicit-str-concat/).
 pub(crate) mod rules;
+pub mod settings;
 
 #[cfg(test)]
 mod tests {
@@ -26,4 +27,24 @@ mod tests {
         insta::assert_yaml_snapshot!(snapshot, diagnostics);
         Ok(())
     }
+
+    #[test_case(Rule::SingleLineImplicitStringConcatenation, Path::new("ISC.py"); "ISC001")]
+    #[test_case(Rule::MultiLineImplicitStringConcatenation, Path::new("ISC.py"); "ISC002")]
+    #[test_case(Rule::ExplicitStringConcatenation, Path::new("ISC.py"); "ISC003")]
+    fn multiline(rule_code: Rule, path: &Path) -> Result<()> {
+        let snapshot = format!("multiline_{}_{}", rule_code.code(), path.to_string_lossy());
+        let diagnostics = test_path(
+            Path::new("./resources/test/fixtures/flake8_implicit_str_concat")
+                .join(path)
+                .as_path(),
+            &settings::Settings {
+                flake8_implicit_str_concat: super::settings::Settings {
+                    allow_multiline: false,
+                },
+                ..settings::Settings::for_rule(rule_code)
+            },
+        )?;
+        insta::assert_yaml_snapshot!(snapshot, diagnostics);
+        Ok(())
+    }
 }

src/rules/flake8_implicit_str_concat/rules.rs

@@ -4,13 +4,20 @@ use rustpython_parser::lexer::{LexResult, Tok};
 
 use crate::ast::types::Range;
 use crate::registry::Diagnostic;
+use crate::rules::flake8_implicit_str_concat::settings::Settings;
 use crate::violations;
 
 /// ISC001, ISC002
-pub fn implicit(tokens: &[LexResult]) -> Vec<Diagnostic> {
+pub fn implicit(tokens: &[LexResult], settings: &Settings) -> Vec<Diagnostic> {
     let mut diagnostics = vec![];
-    for ((a_start, a_tok, a_end), (b_start, b_tok, b_end)) in
+    for ((a_start, a_tok, a_end), (b_start, b_tok, b_end)) in tokens
-        tokens.iter().flatten().tuple_windows()
+        .iter()
+        .flatten()
+        .filter(|(_, tok, _)| {
+            !matches!(tok, Tok::Comment(..))
+                && (settings.allow_multiline || !matches!(tok, Tok::NonLogicalNewline))
+        })
+        .tuple_windows()
     {
         if matches!(a_tok, Tok::String { .. }) && matches!(b_tok, Tok::String { .. }) {
             if a_end.row() == b_start.row() {
@@ -22,8 +29,6 @@ pub fn implicit(tokens: &[LexResult]) -> Vec<Diagnostic> {
                     },
                 ));
             } else {
-                // Not on the same line, and no NonLogicalNewline between a and b =>
-                // concatantion over a continuation line.
                 diagnostics.push(Diagnostic::new(
                     violations::MultiLineImplicitStringConcatenation,
                     Range {

src/rules/flake8_implicit_str_concat/settings.rs

@@ -0,0 +1,57 @@
+//! Settings for the `flake8-implicit-str-concat` plugin.
+
+use ruff_macros::ConfigurationOptions;
+use schemars::JsonSchema;
+use serde::{Deserialize, Serialize};
+
+#[derive(
+    Debug, PartialEq, Eq, Serialize, Deserialize, Default, ConfigurationOptions, JsonSchema,
+)]
+#[serde(
+    deny_unknown_fields,
+    rename_all = "kebab-case",
+    rename = "Flake8ImplicitStrConcatOptions"
+)]
+pub struct Options {
+    #[option(
+        default = r#"true"#,
+        value_type = "bool",
+        example = r#"
+            allow-multiline = false
+        "#
+    )]
+    /// Whether to allow implicit string concatenations for multiline strings.
+    /// By default, implicit concatenations of multiline strings are
+    /// allowed (but continuation lines, delimited with a backslash, are
+    /// prohibited).
+    pub allow_multiline: Option<bool>,
+}
+
+#[derive(Debug, Hash)]
+pub struct Settings {
+    pub allow_multiline: bool,
+}
+
+impl Default for Settings {
+    fn default() -> Self {
+        Self {
+            allow_multiline: true,
+        }
+    }
+}
+
+impl From<Options> for Settings {
+    fn from(options: Options) -> Self {
+        Self {
+            allow_multiline: options.allow_multiline.unwrap_or(true),
+        }
+    }
+}
+
+impl From<Settings> for Options {
+    fn from(settings: Settings) -> Self {
+        Self {
+            allow_multiline: Some(settings.allow_multiline),
+        }
+    }
+}

src/rules/flake8_implicit_str_concat/snapshots/ruff__rules__flake8_implicit_str_concat__tests__multiline_ISC001_ISC.py.snap

@@ -0,0 +1,25 @@
+---
+source: src/rules/flake8_implicit_str_concat/mod.rs
+expression: diagnostics
+---
+- kind:
+    SingleLineImplicitStringConcatenation: ~
+  location:
+    row: 1
+    column: 4
+  end_location:
+    row: 1
+    column: 11
+  fix: ~
+  parent: ~
+- kind:
+    SingleLineImplicitStringConcatenation: ~
+  location:
+    row: 1
+    column: 8
+  end_location:
+    row: 1
+    column: 15
+  fix: ~
+  parent: ~
+

src/rules/flake8_implicit_str_concat/snapshots/ruff__rules__flake8_implicit_str_concat__tests__multiline_ISC002_ISC.py.snap

@@ -0,0 +1,45 @@
+---
+source: src/rules/flake8_implicit_str_concat/mod.rs
+expression: diagnostics
+---
+- kind:
+    MultiLineImplicitStringConcatenation: ~
+  location:
+    row: 5
+    column: 4
+  end_location:
+    row: 6
+    column: 9
+  fix: ~
+  parent: ~
+- kind:
+    MultiLineImplicitStringConcatenation: ~
+  location:
+    row: 24
+    column: 2
+  end_location:
+    row: 25
+    column: 7
+  fix: ~
+  parent: ~
+- kind:
+    MultiLineImplicitStringConcatenation: ~
+  location:
+    row: 29
+    column: 2
+  end_location:
+    row: 30
+    column: 7
+  fix: ~
+  parent: ~
+- kind:
+    MultiLineImplicitStringConcatenation: ~
+  location:
+    row: 34
+    column: 2
+  end_location:
+    row: 35
+    column: 8
+  fix: ~
+  parent: ~
+

src/rules/flake8_implicit_str_concat/snapshots/ruff__rules__flake8_implicit_str_concat__tests__multiline_ISC003_ISC.py.snap

@@ -0,0 +1,45 @@
+---
+source: src/rules/flake8_implicit_str_concat/mod.rs
+expression: diagnostics
+---
+- kind:
+    ExplicitStringConcatenation: ~
+  location:
+    row: 3
+    column: 4
+  end_location:
+    row: 3
+    column: 17
+  fix: ~
+  parent: ~
+- kind:
+    ExplicitStringConcatenation: ~
+  location:
+    row: 9
+    column: 2
+  end_location:
+    row: 10
+    column: 7
+  fix: ~
+  parent: ~
+- kind:
+    ExplicitStringConcatenation: ~
+  location:
+    row: 14
+    column: 2
+  end_location:
+    row: 15
+    column: 7
+  fix: ~
+  parent: ~
+- kind:
+    ExplicitStringConcatenation: ~
+  location:
+    row: 19
+    column: 2
+  end_location:
+    row: 20
+    column: 8
+  fix: ~
+  parent: ~
+

src/settings/configuration.rs

@@ -16,9 +16,9 @@ use crate::fs;
 use crate::registry::RuleSelector;
 use crate::rules::{
     flake8_annotations, flake8_bandit, flake8_bugbear, flake8_builtins, flake8_errmsg,
-    flake8_import_conventions, flake8_pytest_style, flake8_quotes, flake8_tidy_imports,
+    flake8_implicit_str_concat, flake8_import_conventions, flake8_pytest_style, flake8_quotes,
-    flake8_unused_arguments, isort, mccabe, pep8_naming, pycodestyle, pydocstyle, pylint,
+    flake8_tidy_imports, flake8_unused_arguments, isort, mccabe, pep8_naming, pycodestyle,
-    pyupgrade,
+    pydocstyle, pylint, pyupgrade,
 };
 use crate::settings::options::Options;
 use crate::settings::pyproject::load_options;
@@ -65,6 +65,7 @@ pub struct Configuration {
     pub flake8_bugbear: Option<flake8_bugbear::settings::Options>,
     pub flake8_builtins: Option<flake8_builtins::settings::Options>,
     pub flake8_errmsg: Option<flake8_errmsg::settings::Options>,
+    pub flake8_implicit_str_concat: Option<flake8_implicit_str_concat::settings::Options>,
     pub flake8_import_conventions: Option<flake8_import_conventions::settings::Options>,
     pub flake8_pytest_style: Option<flake8_pytest_style::settings::Options>,
     pub flake8_quotes: Option<flake8_quotes::settings::Options>,
@@ -172,6 +173,7 @@ impl Configuration {
             flake8_bugbear: options.flake8_bugbear,
             flake8_builtins: options.flake8_builtins,
             flake8_errmsg: options.flake8_errmsg,
+            flake8_implicit_str_concat: options.flake8_implicit_str_concat,
             flake8_import_conventions: options.flake8_import_conventions,
             flake8_pytest_style: options.flake8_pytest_style,
             flake8_quotes: options.flake8_quotes,
@@ -240,6 +242,9 @@ impl Configuration {
             flake8_bugbear: self.flake8_bugbear.or(config.flake8_bugbear),
             flake8_builtins: self.flake8_builtins.or(config.flake8_builtins),
             flake8_errmsg: self.flake8_errmsg.or(config.flake8_errmsg),
+            flake8_implicit_str_concat: self
+                .flake8_implicit_str_concat
+                .or(config.flake8_implicit_str_concat),
             flake8_import_conventions: self
                 .flake8_import_conventions
                 .or(config.flake8_import_conventions),

src/settings/defaults.rs

@@ -9,9 +9,9 @@ use super::Settings;
 use crate::registry::RuleSelector;
 use crate::rules::{
     flake8_annotations, flake8_bandit, flake8_bugbear, flake8_builtins, flake8_errmsg,
-    flake8_import_conventions, flake8_pytest_style, flake8_quotes, flake8_tidy_imports,
+    flake8_implicit_str_concat, flake8_import_conventions, flake8_pytest_style, flake8_quotes,
-    flake8_unused_arguments, isort, mccabe, pep8_naming, pycodestyle, pydocstyle, pylint,
+    flake8_tidy_imports, flake8_unused_arguments, isort, mccabe, pep8_naming, pycodestyle,
-    pyupgrade,
+    pydocstyle, pylint, pyupgrade,
 };
 
 pub const PREFIXES: &[RuleSelector] = &[RuleSelector::E, RuleSelector::F];
@@ -76,6 +76,7 @@ impl Default for Settings {
             flake8_bugbear: flake8_bugbear::settings::Settings::default(),
             flake8_builtins: flake8_builtins::settings::Settings::default(),
             flake8_errmsg: flake8_errmsg::settings::Settings::default(),
+            flake8_implicit_str_concat: flake8_implicit_str_concat::settings::Settings::default(),
             flake8_import_conventions: flake8_import_conventions::settings::Settings::default(),
             flake8_pytest_style: flake8_pytest_style::settings::Settings::default(),
             flake8_quotes: flake8_quotes::settings::Settings::default(),

src/settings/mod.rs

@@ -17,9 +17,9 @@ use crate::cache::cache_dir;
 use crate::registry::{Rule, RuleSelector, SuffixLength, CATEGORIES, INCOMPATIBLE_CODES};
 use crate::rules::{
     flake8_annotations, flake8_bandit, flake8_bugbear, flake8_builtins, flake8_errmsg,
-    flake8_import_conventions, flake8_pytest_style, flake8_quotes, flake8_tidy_imports,
+    flake8_implicit_str_concat, flake8_import_conventions, flake8_pytest_style, flake8_quotes,
-    flake8_unused_arguments, isort, mccabe, pep8_naming, pycodestyle, pydocstyle, pylint,
+    flake8_tidy_imports, flake8_unused_arguments, isort, mccabe, pep8_naming, pycodestyle,
-    pyupgrade,
+    pydocstyle, pylint, pyupgrade,
 };
 use crate::settings::configuration::Configuration;
 use crate::settings::types::{PerFileIgnore, PythonVersion, SerializationFormat, Version};
@@ -109,6 +109,7 @@ pub struct Settings {
     pub flake8_bugbear: flake8_bugbear::settings::Settings,
     pub flake8_builtins: flake8_builtins::settings::Settings,
     pub flake8_errmsg: flake8_errmsg::settings::Settings,
+    pub flake8_implicit_str_concat: flake8_implicit_str_concat::settings::Settings,
     pub flake8_import_conventions: flake8_import_conventions::settings::Settings,
     pub flake8_pytest_style: flake8_pytest_style::settings::Settings,
     pub flake8_quotes: flake8_quotes::settings::Settings,
@@ -174,6 +175,10 @@ impl Settings {
             flake8_bugbear: config.flake8_bugbear.map(Into::into).unwrap_or_default(),
             flake8_builtins: config.flake8_builtins.map(Into::into).unwrap_or_default(),
             flake8_errmsg: config.flake8_errmsg.map(Into::into).unwrap_or_default(),
+            flake8_implicit_str_concat: config
+                .flake8_implicit_str_concat
+                .map(Into::into)
+                .unwrap_or_default(),
             flake8_import_conventions: config
                 .flake8_import_conventions
                 .map(Into::into)

src/settings/options.rs

@@ -8,9 +8,9 @@ use serde::{Deserialize, Serialize};
 use crate::registry::RuleSelector;
 use crate::rules::{
     flake8_annotations, flake8_bandit, flake8_bugbear, flake8_builtins, flake8_errmsg,
-    flake8_import_conventions, flake8_pytest_style, flake8_quotes, flake8_tidy_imports,
+    flake8_implicit_str_concat, flake8_import_conventions, flake8_pytest_style, flake8_quotes,
-    flake8_unused_arguments, isort, mccabe, pep8_naming, pycodestyle, pydocstyle, pylint,
+    flake8_tidy_imports, flake8_unused_arguments, isort, mccabe, pep8_naming, pycodestyle,
-    pyupgrade,
+    pydocstyle, pylint, pyupgrade,
 };
 use crate::settings::types::{PythonVersion, SerializationFormat, Version};
 
@@ -440,6 +440,9 @@ pub struct Options {
     /// Options for the `flake8-tidy-imports` plugin.
     pub flake8_tidy_imports: Option<flake8_tidy_imports::options::Options>,
     #[option_group]
+    /// Options for the `flake8-implicit-str-concat` plugin.
+    pub flake8_implicit_str_concat: Option<flake8_implicit_str_concat::settings::Options>,
+    #[option_group]
     /// Options for the `flake8-import-conventions` plugin.
     pub flake8_import_conventions: Option<flake8_import_conventions::settings::Options>,
     #[option_group]

src/settings/pyproject.rs

@@ -202,6 +202,7 @@ mod tests {
                     flake8_pytest_style: None,
                     flake8_quotes: None,
                     flake8_tidy_imports: None,
+                    flake8_implicit_str_concat: None,
                     flake8_import_conventions: None,
                     flake8_unused_arguments: None,
                     isort: None,
@@ -264,6 +265,7 @@ line-length = 79
                     flake8_pytest_style: None,
                     flake8_quotes: None,
                     flake8_tidy_imports: None,
+                    flake8_implicit_str_concat: None,
                     flake8_import_conventions: None,
                     flake8_unused_arguments: None,
                     isort: None,
@@ -326,6 +328,7 @@ exclude = ["foo.py"]
                     flake8_pytest_style: None,
                     flake8_quotes: None,
                     flake8_tidy_imports: None,
+                    flake8_implicit_str_concat: None,
                     flake8_import_conventions: None,
                     flake8_unused_arguments: None,
                     isort: None,
@@ -388,6 +391,7 @@ select = ["E501"]
                     flake8_pytest_style: None,
                     flake8_quotes: None,
                     flake8_tidy_imports: None,
+                    flake8_implicit_str_concat: None,
                     flake8_import_conventions: None,
                     flake8_unused_arguments: None,
                     isort: None,
@@ -451,6 +455,7 @@ ignore = ["E501"]
                     flake8_pytest_style: None,
                     flake8_quotes: None,
                     flake8_tidy_imports: None,
+                    flake8_implicit_str_concat: None,
                     flake8_import_conventions: None,
                     flake8_unused_arguments: None,
                     isort: None,
@@ -582,6 +587,7 @@ other-attribute = 1
                     ]),
                     mark_parentheses: Some(false),
                 }),
+                flake8_implicit_str_concat: None,
                 flake8_quotes: Some(flake8_quotes::settings::Options {
                     inline_quotes: Some(Quote::Single),
                     multiline_quotes: Some(Quote::Double),