Change the compatible strategy to use ~= operator

news/225.feature

+Change the behavior of `--save-compatible` slightly. Now the version specifier saved is using the REAL compatible operator `~=` as described in PEP 440. Before: `requests<3.0.0,>=2.19.1`, After: `requests~=2.19`. The new specifier accepts `requests==2.19.0` as compatible version.

pdm/cli/utils.py

@@ -19,7 +19,7 @@ from pdm.formats.base import make_inline_table
 from pdm.iostream import stream
 from pdm.models.environment import WorkingSet
 from pdm.models.requirements import Requirement, strip_extras
-from pdm.models.specifiers import bump_version, get_specifier
+from pdm.models.specifiers import get_specifier
 from pdm.project import Project
 
 if TYPE_CHECKING:
@@ -376,10 +376,8 @@ def save_version_specifiers(
                 r.specifier = get_specifier(f"=={resolved[name].version}")
             elif save_strategy == "compatible":
                 version = str(resolved[name].version)
-                next_major_version = ".".join(
-                    map(str, bump_version(tuple(version.split(".")), 0))
-                )
-                r.specifier = get_specifier(f">={version},<{next_major_version}")
+                compatible_version = ".".join((version.split(".") + ["0"])[:2])
+                r.specifier = get_specifier(f"~={compatible_version}")
 
 
 def check_project_file(project: Project) -> None:

tests/cli/test_actions.py

@@ -76,7 +76,7 @@ def test_add_package(project, repository, working_set, is_dev):
     actions.do_add(project, is_dev, packages=["requests"])
     section = "dev-dependencies" if is_dev else "dependencies"
 
-    assert project.meta[section][0] == "requests<3.0.0,>=2.19.1"
+    assert project.meta[section][0] == "requests~=2.19"
     locked_candidates = project.get_locked_candidates("dev" if is_dev else "default")
     assert locked_candidates["idna"].version == "2.7"
     for package in ("requests", "idna", "chardet", "urllib3", "certifi"):
@@ -435,15 +435,15 @@ def test_update_unconstrained_without_packages(project, repository, working_set)
 
 def test_update_ignore_constraints(project, repository, working_set):
     actions.do_add(project, packages=("pytz",))
-    assert project.meta.dependencies == ["pytz<2020.0.0,>=2019.3"]
+    assert project.meta.dependencies == ["pytz~=2019.3"]
     repository.add_candidate("pytz", "2020.2")
 
     actions.do_update(project, unconstrained=False, packages=("pytz",))
-    assert project.meta.dependencies == ["pytz<2020.0.0,>=2019.3"]
+    assert project.meta.dependencies == ["pytz~=2019.3"]
     assert project.get_locked_candidates()["pytz"].version == "2019.3"
 
     actions.do_update(project, unconstrained=True, packages=("pytz",))
-    assert project.meta.dependencies == ["pytz<2021.0.0,>=2020.2"]
+    assert project.meta.dependencies == ["pytz~=2020.2"]
     assert project.get_locked_candidates()["pytz"].version == "2020.2"