`from __future__ import annotations` now implies 3.7+ (#2690)

diff --git a/CHANGES.md b/CHANGES.md
index 0dcf35ea199932b8f22d678d537351440c1a6634..87e36f4dbe7e7b57cb22ebe63c5be012aec67344 100644 (file)
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -15,6 +15,7 @@
 - Fix determination of f-string expression spans (#2654)
 - Fix bad formatting of error messages about EOF in multi-line statements (#2343)
 - Functions and classes in blocks now have more consistent surrounding spacing (#2472)
 - Fix determination of f-string expression spans (#2654)
 - Fix bad formatting of error messages about EOF in multi-line statements (#2343)
 - Functions and classes in blocks now have more consistent surrounding spacing (#2472)

+- `from __future__ import annotations` statement now implies Python 3.7+ (#2690)

 
 #### Jupyter Notebook support
 
 
 #### Jupyter Notebook support
 

diff --git a/src/black/__init__.py b/src/black/__init__.py
index e2376c45617469d7890c0036c15fc4ac7139c27b..59018d00de469c5e276a98f84cca506e44c29d80 100644 (file)
--- a/src/black/__init__.py
+++ b/src/black/__init__.py
@@ -40,7 +40,7 @@ from black.nodes import STARS, syms, is_simple_decorator_expression
 from black.lines import Line, EmptyLineTracker
 from black.linegen import transform_line, LineGenerator, LN
 from black.comments import normalize_fmt_off
 from black.lines import Line, EmptyLineTracker
 from black.linegen import transform_line, LineGenerator, LN
 from black.comments import normalize_fmt_off

-from black.mode import Mode, TargetVersion
+from black.mode import FUTURE_FLAG_TO_FEATURE, Mode, TargetVersion

 from black.mode import Feature, supports_feature, VERSION_TO_FEATURES
 from black.cache import read_cache, write_cache, get_cache_info, filter_cached, Cache
 from black.concurrency import cancel, shutdown, maybe_install_uvloop
 from black.mode import Feature, supports_feature, VERSION_TO_FEATURES
 from black.cache import read_cache, write_cache, get_cache_info, filter_cached, Cache
 from black.concurrency import cancel, shutdown, maybe_install_uvloop


@@ -1080,7 +1080,7 @@ def format_str(src_contents: str, *, mode: Mode) -> FileContent:
     if mode.target_versions:
         versions = mode.target_versions
     else:
     if mode.target_versions:
         versions = mode.target_versions
     else:

-        versions = detect_target_versions(src_node)
+        versions = detect_target_versions(src_node, future_imports=future_imports)

 
     # TODO: fully drop support and this code hopefully in January 2022 :D
     if TargetVersion.PY27 in mode.target_versions or versions == {TargetVersion.PY27}:
 
     # TODO: fully drop support and this code hopefully in January 2022 :D
     if TargetVersion.PY27 in mode.target_versions or versions == {TargetVersion.PY27}:


@@ -1132,7 +1132,9 @@ def decode_bytes(src: bytes) -> Tuple[FileContent, Encoding, NewLine]:
         return tiow.read(), encoding, newline
 
 
         return tiow.read(), encoding, newline
 
 

-def get_features_used(node: Node) -> Set[Feature]:  # noqa: C901
+def get_features_used(  # noqa: C901
+    node: Node, *, future_imports: Optional[Set[str]] = None
+) -> Set[Feature]:

     """Return a set of (relatively) new Python features used in this file.
 
     Currently looking for:
     """Return a set of (relatively) new Python features used in this file.
 
     Currently looking for:


@@ -1142,9 +1144,17 @@ def get_features_used(node: Node) -> Set[Feature]:  # noqa: C901
     - positional only arguments in function signatures and lambdas;
     - assignment expression;
     - relaxed decorator syntax;
     - positional only arguments in function signatures and lambdas;
     - assignment expression;
     - relaxed decorator syntax;

+    - usage of __future__ flags (annotations);

     - print / exec statements;
     """
     features: Set[Feature] = set()
     - print / exec statements;
     """
     features: Set[Feature] = set()

+    if future_imports:
+        features |= {
+            FUTURE_FLAG_TO_FEATURE[future_import]
+            for future_import in future_imports
+            if future_import in FUTURE_FLAG_TO_FEATURE
+        }
+

     for n in node.pre_order():
         if n.type == token.STRING:
             value_head = n.value[:2]  # type: ignore
     for n in node.pre_order():
         if n.type == token.STRING:
             value_head = n.value[:2]  # type: ignore


@@ -1229,9 +1239,11 @@ def get_features_used(node: Node) -> Set[Feature]:  # noqa: C901
     return features
 
 
     return features
 
 

-def detect_target_versions(node: Node) -> Set[TargetVersion]:
+def detect_target_versions(
+    node: Node, *, future_imports: Optional[Set[str]] = None
+) -> Set[TargetVersion]:

     """Detect the version to target based on the nodes used."""
     """Detect the version to target based on the nodes used."""

-    features = get_features_used(node)
+    features = get_features_used(node, future_imports=future_imports)

     return {
         version for version in TargetVersion if features <= VERSION_TO_FEATURES[version]
     }
     return {
         version for version in TargetVersion if features <= VERSION_TO_FEATURES[version]
     }

diff --git a/src/black/mode.py b/src/black/mode.py
index e2417531240b7c38ae0a61d782a84f9cdf9ee7fd..a2b7d9e9e2d8708e49e2733aa4811b53c7fc547d 100644 (file)
--- a/src/black/mode.py
+++ b/src/black/mode.py
@@ -4,11 +4,18 @@ Mostly around Python language feature support per version and Black configuratio
 chosen by the user.
 """
 
 chosen by the user.
 """
 

+import sys
+

 from dataclasses import dataclass, field
 from enum import Enum
 from operator import attrgetter
 from typing import Dict, Set
 
 from dataclasses import dataclass, field
 from enum import Enum
 from operator import attrgetter
 from typing import Dict, Set
 

+if sys.version_info < (3, 8):
+    from typing_extensions import Final
+else:
+    from typing import Final
+

 from black.const import DEFAULT_LINE_LENGTH
 
 
 from black.const import DEFAULT_LINE_LENGTH
 
 


@@ -44,6 +51,9 @@ class Feature(Enum):
     PATTERN_MATCHING = 11
     FORCE_OPTIONAL_PARENTHESES = 50
 
     PATTERN_MATCHING = 11
     FORCE_OPTIONAL_PARENTHESES = 50
 

+    # __future__ flags
+    FUTURE_ANNOTATIONS = 51
+

     # temporary for Python 2 deprecation
     PRINT_STMT = 200
     EXEC_STMT = 201
     # temporary for Python 2 deprecation
     PRINT_STMT = 200
     EXEC_STMT = 201


@@ -55,6 +65,11 @@ class Feature(Enum):
     BACKQUOTE_REPR = 207
 
 
     BACKQUOTE_REPR = 207
 
 

+FUTURE_FLAG_TO_FEATURE: Final = {
+    "annotations": Feature.FUTURE_ANNOTATIONS,
+}
+
+

 VERSION_TO_FEATURES: Dict[TargetVersion, Set[Feature]] = {
     TargetVersion.PY27: {
         Feature.ASYNC_IDENTIFIERS,
 VERSION_TO_FEATURES: Dict[TargetVersion, Set[Feature]] = {
     TargetVersion.PY27: {
         Feature.ASYNC_IDENTIFIERS,


@@ -89,6 +104,7 @@ VERSION_TO_FEATURES: Dict[TargetVersion, Set[Feature]] = {
         Feature.TRAILING_COMMA_IN_CALL,
         Feature.TRAILING_COMMA_IN_DEF,
         Feature.ASYNC_KEYWORDS,
         Feature.TRAILING_COMMA_IN_CALL,
         Feature.TRAILING_COMMA_IN_DEF,
         Feature.ASYNC_KEYWORDS,

+        Feature.FUTURE_ANNOTATIONS,

     },
     TargetVersion.PY38: {
         Feature.UNICODE_LITERALS,
     },
     TargetVersion.PY38: {
         Feature.UNICODE_LITERALS,


@@ -97,6 +113,7 @@ VERSION_TO_FEATURES: Dict[TargetVersion, Set[Feature]] = {
         Feature.TRAILING_COMMA_IN_CALL,
         Feature.TRAILING_COMMA_IN_DEF,
         Feature.ASYNC_KEYWORDS,
         Feature.TRAILING_COMMA_IN_CALL,
         Feature.TRAILING_COMMA_IN_DEF,
         Feature.ASYNC_KEYWORDS,

+        Feature.FUTURE_ANNOTATIONS,

         Feature.ASSIGNMENT_EXPRESSIONS,
         Feature.POS_ONLY_ARGUMENTS,
     },
         Feature.ASSIGNMENT_EXPRESSIONS,
         Feature.POS_ONLY_ARGUMENTS,
     },


@@ -107,6 +124,7 @@ VERSION_TO_FEATURES: Dict[TargetVersion, Set[Feature]] = {
         Feature.TRAILING_COMMA_IN_CALL,
         Feature.TRAILING_COMMA_IN_DEF,
         Feature.ASYNC_KEYWORDS,
         Feature.TRAILING_COMMA_IN_CALL,
         Feature.TRAILING_COMMA_IN_DEF,
         Feature.ASYNC_KEYWORDS,

+        Feature.FUTURE_ANNOTATIONS,

         Feature.ASSIGNMENT_EXPRESSIONS,
         Feature.RELAXED_DECORATORS,
         Feature.POS_ONLY_ARGUMENTS,
         Feature.ASSIGNMENT_EXPRESSIONS,
         Feature.RELAXED_DECORATORS,
         Feature.POS_ONLY_ARGUMENTS,


@@ -118,6 +136,7 @@ VERSION_TO_FEATURES: Dict[TargetVersion, Set[Feature]] = {
         Feature.TRAILING_COMMA_IN_CALL,
         Feature.TRAILING_COMMA_IN_DEF,
         Feature.ASYNC_KEYWORDS,
         Feature.TRAILING_COMMA_IN_CALL,
         Feature.TRAILING_COMMA_IN_DEF,
         Feature.ASYNC_KEYWORDS,

+        Feature.FUTURE_ANNOTATIONS,

         Feature.ASSIGNMENT_EXPRESSIONS,
         Feature.RELAXED_DECORATORS,
         Feature.POS_ONLY_ARGUMENTS,
         Feature.ASSIGNMENT_EXPRESSIONS,
         Feature.RELAXED_DECORATORS,
         Feature.POS_ONLY_ARGUMENTS,

diff --git a/tests/test_black.py b/tests/test_black.py
index 92598532e2c4086b794dcbaa27e83e6b52ec294f..2d0a7dfd4e233ebecc906115c637e15dfcc145ba 100644 (file)
--- a/tests/test_black.py
+++ b/tests/test_black.py
@@ -811,6 +811,24 @@ class BlackTestCase(BlackBaseTestCase):
         node = black.lib2to3_parse("def fn(a, /, b): ...")
         self.assertEqual(black.get_features_used(node), {Feature.POS_ONLY_ARGUMENTS})
 
         node = black.lib2to3_parse("def fn(a, /, b): ...")
         self.assertEqual(black.get_features_used(node), {Feature.POS_ONLY_ARGUMENTS})
 

+    def test_get_features_used_for_future_flags(self) -> None:
+        for src, features in [
+            ("from __future__ import annotations", {Feature.FUTURE_ANNOTATIONS}),
+            (
+                "from __future__ import (other, annotations)",
+                {Feature.FUTURE_ANNOTATIONS},
+            ),
+            ("a = 1 + 2\nfrom something import annotations", set()),
+            ("from __future__ import x, y", set()),
+        ]:
+            with self.subTest(src=src, features=features):
+                node = black.lib2to3_parse(src)
+                future_imports = black.get_future_imports(node)
+                self.assertEqual(
+                    black.get_features_used(node, future_imports=future_imports),
+                    features,
+                )
+

     def test_get_future_imports(self) -> None:
         node = black.lib2to3_parse("\n")
         self.assertEqual(set(), black.get_future_imports(node))
     def test_get_future_imports(self) -> None:
         node = black.lib2to3_parse("\n")
         self.assertEqual(set(), black.get_future_imports(node))