semver: improve constraint parsing (python-poetry#327)

This change replaces the custom regex used with
`packaging.version.VERSION_PATTERN` for consistency with other parts of
the code base. Additionally, this fixes previous issues with parsing
pre-release dev releases etc.

Author: abn

src/poetry/core/semver/helpers.py

@@ -63,26 +63,18 @@ def parse_single_constraint(constraint: str) -> VersionConstraint:
     # Tilde range
     m = TILDE_CONSTRAINT.match(constraint)
     if m:
-        version = Version.parse(m.group(1))
+        version = Version.parse(m.group("version"))
         high = version.stable.next_minor()
-        if len(m.group(1).split(".")) == 1:
+        if version.release.precision == 1:
             high = version.stable.next_major()
 
         return VersionRange(version, high, include_min=True)
 
     # PEP 440 Tilde range (~=)
     m = TILDE_PEP440_CONSTRAINT.match(constraint)
     if m:
-        precision = 1
-        if m.group(3):
-            precision += 1
-
-            if m.group(4):
-                precision += 1
-
-        version = Version.parse(m.group(1))
-
-        if precision == 2:
+        version = Version.parse(m.group("version"))
+        if version.release.precision == 2:
             high = version.stable.next_major()
         else:
             high = version.stable.next_minor()
@@ -92,14 +84,14 @@ def parse_single_constraint(constraint: str) -> VersionConstraint:
     # Caret range
     m = CARET_CONSTRAINT.match(constraint)
     if m:
-        version = Version.parse(m.group(1))
+        version = Version.parse(m.group("version"))
 
         return VersionRange(version, version.next_breaking(), include_min=True)
 
     # X Range
     m = X_CONSTRAINT.match(constraint)
     if m:
-        op = m.group(1)
+        op = m.group("op")
         major = int(m.group(2))
         minor = m.group(3)
 
@@ -124,15 +116,8 @@ def parse_single_constraint(constraint: str) -> VersionConstraint:
     # Basic comparator
     m = BASIC_CONSTRAINT.match(constraint)
     if m:
-        op = m.group(1)
-        version_string = m.group(2)
-
-        # Technically invalid constraints like `>= 3.*` will appear
-        # here as `3.`.
-        # Pip currently supports these and to avoid breaking existing
-        # users workflows we need to support them as well. To do so,
-        # we just remove the inconsequential part.
-        version_string = version_string.rstrip(".")
+        op = m.group("op")
+        version_string = m.group("version")
 
         if version_string == "dev":
             version_string = "0.0-dev"

src/poetry/core/semver/patterns.py

@@ -2,21 +2,27 @@
 
 import re
 
+from packaging.version import VERSION_PATTERN
 
-MODIFIERS = (
-    "[._-]?"
-    r"((?!post)(?:beta|b|c|pre|RC|alpha|a|patch|pl|p|dev)(?:(?:[.-]?\d+)*)?)?"
-    r"([+-]?([0-9A-Za-z-]+(\.[0-9A-Za-z-]+)*))?"
-)
 
-_COMPLETE_VERSION = (
-    rf"v?(?:\d+!)?(\d+)(?:\.(\d+))?(?:\.(\d+))?(?:\.(\d+))?{MODIFIERS}(?:\+[^\s]+)?"
-)
+COMPLETE_VERSION = re.compile(VERSION_PATTERN, re.VERBOSE | re.IGNORECASE)
 
-COMPLETE_VERSION = re.compile("(?i)" + _COMPLETE_VERSION)
+CARET_CONSTRAINT = re.compile(
+    rf"^\^(?P<version>{VERSION_PATTERN})$", re.VERBOSE | re.IGNORECASE
+)
+TILDE_CONSTRAINT = re.compile(
+    rf"^~(?!=)\s*(?P<version>{VERSION_PATTERN})$", re.VERBOSE | re.IGNORECASE
+)
+TILDE_PEP440_CONSTRAINT = re.compile(
+    rf"^~=\s*(?P<version>{VERSION_PATTERN})$", re.VERBOSE | re.IGNORECASE
+)
+X_CONSTRAINT = re.compile(
+    r"^(?P<op>!=|==)?\s*v?(\d+)(?:\.(\d+))?(?:\.(\d+))?(?:\.[xX*])+$"
+)
 
-CARET_CONSTRAINT = re.compile(rf"(?i)^\^({_COMPLETE_VERSION})$")
-TILDE_CONSTRAINT = re.compile(rf"(?i)^~(?!=)\s*({_COMPLETE_VERSION})$")
-TILDE_PEP440_CONSTRAINT = re.compile(rf"(?i)^~=\s*({_COMPLETE_VERSION})$")
-X_CONSTRAINT = re.compile(r"^(!=|==)?\s*v?(\d+)(?:\.(\d+))?(?:\.(\d+))?(?:\.[xX*])+$")
-BASIC_CONSTRAINT = re.compile(rf"(?i)^(<>|!=|>=?|<=?|==?)?\s*({_COMPLETE_VERSION}|dev)")
+# note that we also allow technically incorrect version patterns with astrix (eg: 3.5.*)
+# as this is supported by pip and appears in metadata within python packages
+BASIC_CONSTRAINT = re.compile(
+    rf"^(?P<op><>|!=|>=?|<=?|==?)?\s*(?P<version>{VERSION_PATTERN}|dev)(\.\*)?$",
+    re.VERBOSE | re.IGNORECASE,
+)

tests/semver/test_parse_constraint.py

@@ -28,6 +28,14 @@
                 include_min=True,
             ),
         ),
+        (
+            "== 3.8.x",
+            VersionRange(
+                min=Version.from_parts(3, 8),
+                max=Version.from_parts(3, 9, 0),
+                include_min=True,
+            ),
+        ),
         (
             "~= 3.8",
             VersionRange(
@@ -182,6 +190,28 @@
                 include_min=True,
             ),
         ),
+        (
+            "^1.0.0a1.dev0",
+            VersionRange(
+                min=Version.from_parts(
+                    1, 0, 0, pre=ReleaseTag("a", 1), dev=ReleaseTag("dev", 0)
+                ),
+                max=Version.from_parts(2, 0, 0),
+                include_min=True,
+            ),
+        ),
+        (
+            "1.0.0a1.dev0",
+            VersionRange(
+                min=Version.from_parts(
+                    1, 0, 0, pre=ReleaseTag("a", 1), dev=ReleaseTag("dev", 0)
+                ),
+                max=Version.from_parts(
+                    1, 0, 0, pre=ReleaseTag("a", 1), dev=ReleaseTag("dev", 0)
+                ),
+                include_min=True,
+            ),
+        ),
         (
             "~1.0.0a1",
             VersionRange(
@@ -190,6 +220,16 @@
                 include_min=True,
             ),
         ),
+        (
+            "~1.0.0a1.dev0",
+            VersionRange(
+                min=Version.from_parts(
+                    1, 0, 0, pre=ReleaseTag("a", 1), dev=ReleaseTag("dev", 0)
+                ),
+                max=Version.from_parts(1, 1, 0),
+                include_min=True,
+            ),
+        ),
         (
             "^0",
             VersionRange(
@@ -208,7 +248,9 @@
         ),
     ],
 )
+@pytest.mark.parametrize(("with_whitespace_padding",), [(True,), (False,)])
 def test_parse_constraint(
-    constraint: str, version: VersionRange | VersionUnion
+    constraint: str, version: VersionRange | VersionUnion, with_whitespace_padding: bool
 ) -> None:
-    assert parse_constraint(constraint) == version
+    padding = " " * (4 if with_whitespace_padding else 0)
+    assert parse_constraint(f"{padding}{constraint}{padding}") == version

tests/version/test_requirements.py

@@ -43,6 +43,7 @@ def assert_requirement(
         ("name<3.*", {"name": "name", "constraint": "<3.0"}),
         ("name>3.5.*", {"name": "name", "constraint": ">3.5"}),
         ("name==1.0.post1", {"name": "name", "constraint": "==1.0.post1"}),
+        ("name==1.2.0b1.dev0", {"name": "name", "constraint": "==1.2.0b1.dev0"}),
         (
             "name>=1.2.3;python_version=='2.6'",
             {