[isort] Check full module path against project root(s) when categorizing first-party (#16565)

When attempting to determine whether `import foo.bar.baz` is a known
first-party import relative to [user-provided source
paths](https://docs.astral.sh/ruff/settings/#src), when `preview` is
enabled we now check that `SRC/foo/bar/baz` is a directory or
`SRC/foo/bar/baz.py` or `SRC/foo/bar/baz.pyi` exist.

Previously, we just checked the analogous thing for `SRC/foo`, but this
can be misleading in situations with disjoint namespace packages that
share a common base name (e.g. we may be working inside the namespace
package `foo.buzz` and importing `foo.bar` from elsewhere).

Supersedes #12987 
Closes #12984

Author: dylwil3

Cargo.lock

@@ -5,7 +5,6 @@ info:
   args:
     - rule
     - F401
-snapshot_kind: text
 ---
 success: true
 exit_code: 0
@@ -84,6 +83,11 @@ else:
     print("numpy is not installed")
 ```
 
+## Preview
+When [preview](https://docs.astral.sh/ruff/preview/) is enabled,
+the criterion for determining whether an import is first-party
+is stricter, which could affect the suggested fix. See [this FAQ section](https://docs.astral.sh/ruff/faq/#how-does-ruff-determine-which-of-my-imports-are-first-party-third-party-etc) for more details.
+
 ## Options
 - `lint.ignore-init-module-imports`
 - `lint.pyflakes.allowed-unused-imports`

crates/ruff/tests/snapshots/integration_test__rule_f401.snap

@@ -76,6 +76,7 @@ insta = { workspace = true, features = ["filters", "json", "redactions"] }
 test-case = { workspace = true }
 # Disable colored output in tests
 colored = { workspace = true, features = ["no-color"] }
+tempfile = { workspace = true }
 
 [features]
 default = []

crates/ruff_linter/Cargo.toml

@@ -81,7 +81,7 @@ expression: value
           "rules": [
             {
               "fullDescription": {
-                "text": "## What it does\nChecks for unused imports.\n\n## Why is this bad?\nUnused imports add a performance overhead at runtime, and risk creating\nimport cycles. They also increase the cognitive load of reading the code.\n\nIf an import statement is used to check for the availability or existence\nof a module, consider using `importlib.util.find_spec` instead.\n\nIf an import statement is used to re-export a symbol as part of a module's\npublic interface, consider using a \"redundant\" import alias, which\ninstructs Ruff (and other tools) to respect the re-export, and avoid\nmarking it as unused, as in:\n\n```python\nfrom module import member as member\n```\n\nAlternatively, you can use `__all__` to declare a symbol as part of the module's\ninterface, as in:\n\n```python\n# __init__.py\nimport some_module\n\n__all__ = [\"some_module\"]\n```\n\n## Fix safety\n\nFixes to remove unused imports are safe, except in `__init__.py` files.\n\nApplying fixes to `__init__.py` files is currently in preview. The fix offered depends on the\ntype of the unused import. Ruff will suggest a safe fix to export first-party imports with\neither a redundant alias or, if already present in the file, an `__all__` entry. If multiple\n`__all__` declarations are present, Ruff will not offer a fix. Ruff will suggest an unsafe fix\nto remove third-party and standard library imports -- the fix is unsafe because the module's\ninterface changes.\n\n## Example\n\n```python\nimport numpy as np  # unused import\n\n\ndef area(radius):\n    return 3.14 * radius**2\n```\n\nUse instead:\n\n```python\ndef area(radius):\n    return 3.14 * radius**2\n```\n\nTo check the availability of a module, use `importlib.util.find_spec`:\n\n```python\nfrom importlib.util import find_spec\n\nif find_spec(\"numpy\") is not None:\n    print(\"numpy is installed\")\nelse:\n    print(\"numpy is not installed\")\n```\n\n## Options\n- `lint.ignore-init-module-imports`\n- `lint.pyflakes.allowed-unused-imports`\n\n## References\n- [Python documentation: `import`](https://docs.python.org/3/reference/simple_stmts.html#the-import-statement)\n- [Python documentation: `importlib.util.find_spec`](https://docs.python.org/3/library/importlib.html#importlib.util.find_spec)\n- [Typing documentation: interface conventions](https://typing.python.org/en/latest/source/libraries.html#library-interface-public-and-private-symbols)\n"
+                "text": "## What it does\nChecks for unused imports.\n\n## Why is this bad?\nUnused imports add a performance overhead at runtime, and risk creating\nimport cycles. They also increase the cognitive load of reading the code.\n\nIf an import statement is used to check for the availability or existence\nof a module, consider using `importlib.util.find_spec` instead.\n\nIf an import statement is used to re-export a symbol as part of a module's\npublic interface, consider using a \"redundant\" import alias, which\ninstructs Ruff (and other tools) to respect the re-export, and avoid\nmarking it as unused, as in:\n\n```python\nfrom module import member as member\n```\n\nAlternatively, you can use `__all__` to declare a symbol as part of the module's\ninterface, as in:\n\n```python\n# __init__.py\nimport some_module\n\n__all__ = [\"some_module\"]\n```\n\n## Fix safety\n\nFixes to remove unused imports are safe, except in `__init__.py` files.\n\nApplying fixes to `__init__.py` files is currently in preview. The fix offered depends on the\ntype of the unused import. Ruff will suggest a safe fix to export first-party imports with\neither a redundant alias or, if already present in the file, an `__all__` entry. If multiple\n`__all__` declarations are present, Ruff will not offer a fix. Ruff will suggest an unsafe fix\nto remove third-party and standard library imports -- the fix is unsafe because the module's\ninterface changes.\n\n## Example\n\n```python\nimport numpy as np  # unused import\n\n\ndef area(radius):\n    return 3.14 * radius**2\n```\n\nUse instead:\n\n```python\ndef area(radius):\n    return 3.14 * radius**2\n```\n\nTo check the availability of a module, use `importlib.util.find_spec`:\n\n```python\nfrom importlib.util import find_spec\n\nif find_spec(\"numpy\") is not None:\n    print(\"numpy is installed\")\nelse:\n    print(\"numpy is not installed\")\n```\n\n## Preview\nWhen [preview](https://docs.astral.sh/ruff/preview/) is enabled,\nthe criterion for determining whether an import is first-party\nis stricter, which could affect the suggested fix. See [this FAQ section](https://docs.astral.sh/ruff/faq/#how-does-ruff-determine-which-of-my-imports-are-first-party-third-party-etc) for more details.\n\n## Options\n- `lint.ignore-init-module-imports`\n- `lint.pyflakes.allowed-unused-imports`\n\n## References\n- [Python documentation: `import`](https://docs.python.org/3/reference/simple_stmts.html#the-import-statement)\n- [Python documentation: `importlib.util.find_spec`](https://docs.python.org/3/library/importlib.html#importlib.util.find_spec)\n- [Typing documentation: interface conventions](https://typing.python.org/en/latest/source/libraries.html#library-interface-public-and-private-symbols)\n"
               },
               "help": {
                 "text": "`{name}` imported but unused; consider using `importlib.util.find_spec` to test for availability"

crates/ruff_linter/src/message/snapshots/ruff_linter__message__sarif__tests__results.snap

@@ -22,6 +22,11 @@ pub(crate) const fn is_py314_support_enabled(settings: &LinterSettings) -> bool
     settings.preview.is_enabled()
 }
 
+// https://github.com/astral-sh/ruff/pull/16565
+pub(crate) const fn is_full_path_match_source_strategy_enabled(settings: &LinterSettings) -> bool {
+    settings.preview.is_enabled()
+}
+
 // Rule-specific behavior
 
 // https://github.com/astral-sh/ruff/pull/17136

crates/ruff_linter/src/preview.rs

@@ -12,10 +12,12 @@ use crate::checkers::ast::Checker;
 use crate::codes::Rule;
 use crate::fix;
 use crate::importer::ImportedMembers;
+use crate::preview::is_full_path_match_source_strategy_enabled;
 use crate::rules::flake8_type_checking::helpers::{
     filter_contained, is_typing_reference, quote_annotation,
 };
 use crate::rules::flake8_type_checking::imports::ImportBinding;
+use crate::rules::isort::categorize::MatchSourceStrategy;
 use crate::rules::isort::{categorize, ImportSection, ImportType};
 
 /// ## What it does
@@ -63,6 +65,12 @@ use crate::rules::isort::{categorize, ImportSection, ImportType};
 ///     return len(sized)
 /// ```
 ///
+///
+/// ## Preview
+/// When [preview](https://docs.astral.sh/ruff/preview/) is enabled,
+/// the criterion for determining whether an import is first-party
+/// is stricter, which could affect whether this lint is triggered vs [`TC001`](https://docs.astral.sh/ruff/rules/typing-only-third-party-import/). See [this FAQ section](https://docs.astral.sh/ruff/faq/#how-does-ruff-determine-which-of-my-imports-are-first-party-third-party-etc) for more details.
+///
 /// ## Options
 /// - `lint.flake8-type-checking.quote-annotations`
 /// - `lint.flake8-type-checking.runtime-evaluated-base-classes`
@@ -138,6 +146,11 @@ impl Violation for TypingOnlyFirstPartyImport {
 ///     return len(df)
 /// ```
 ///
+/// ## Preview
+/// When [preview](https://docs.astral.sh/ruff/preview/) is enabled,
+/// the criterion for determining whether an import is first-party
+/// is stricter, which could affect whether this lint is triggered vs [`TC001`](https://docs.astral.sh/ruff/rules/typing-only-first-party-import/). See [this FAQ section](https://docs.astral.sh/ruff/faq/#how-does-ruff-determine-which-of-my-imports-are-first-party-third-party-etc) for more details.
+///
 /// ## Options
 /// - `lint.flake8-type-checking.quote-annotations`
 /// - `lint.flake8-type-checking.runtime-evaluated-base-classes`
@@ -299,9 +312,18 @@ pub(crate) fn typing_only_runtime_import(
                 continue;
             }
 
+            let source_name = import.source_name().join(".");
+
             // Categorize the import, using coarse-grained categorization.
+            let match_source_strategy =
+                if is_full_path_match_source_strategy_enabled(checker.settings) {
+                    MatchSourceStrategy::FullPath
+                } else {
+                    MatchSourceStrategy::Root
+                };
+
             let import_type = match categorize(
-                &qualified_name.to_string(),
+                &source_name,
                 qualified_name.is_unresolved_import(),
                 &checker.settings.src,
                 checker.package(),
@@ -311,6 +333,7 @@ pub(crate) fn typing_only_runtime_import(
                 checker.settings.isort.no_sections,
                 &checker.settings.isort.section_order,
                 &checker.settings.isort.default_section,
+                match_source_strategy,
             ) {
                 ImportSection::Known(ImportType::LocalFolder | ImportType::FirstParty) => {
                     ImportType::FirstParty