Fix an infinite loop in the solver (#6178)

Author: dimbleby

src/poetry/mixology/version_solver.py

@@ -513,11 +513,9 @@ def _get_locked(
         locked = self._locked.get(dependency.name, [])
         for dependency_package in locked:
             package = dependency_package.package
-            if (allow_similar or dependency.is_same_package_as(package)) and (
-                dependency.constraint.allows(package.version)
-                or package.is_prerelease()
-                and dependency.constraint.allows(package.version.next_patch())
-            ):
+            if (
+                allow_similar or dependency.is_same_package_as(package)
+            ) and dependency.constraint.allows(package.version):
                 return DependencyPackage(dependency, package)
         return None
 

src/poetry/puzzle/provider.py

@@ -46,7 +46,6 @@
     from poetry.core.packages.directory_dependency import DirectoryDependency
     from poetry.core.packages.file_dependency import FileDependency
     from poetry.core.packages.package import Package
-    from poetry.core.packages.specification import PackageSpecification
     from poetry.core.packages.url_dependency import URLDependency
     from poetry.core.packages.vcs_dependency import VCSDependency
     from poetry.core.semver.version_constraint import VersionConstraint
@@ -193,11 +192,11 @@ def validate_package_for_dependency(
 
     def search_for_installed_packages(
         self,
-        specification: PackageSpecification,
+        dependency: Dependency,
     ) -> list[Package]:
         """
-        Search for installed packages, when available, that provides the given
-        specification.
+        Search for installed packages, when available, that satisfy the given
+        dependency.
 
         This is useful when dealing with packages that are under development, not
         published on package sources and/or only available via system installations.
@@ -207,17 +206,17 @@ def search_for_installed_packages(
 
         logger.debug(
             "Falling back to installed packages to discover metadata for <c2>%s</>",
-            specification.complete_name,
+            dependency.complete_name,
         )
         packages = [
             package
             for package in self._installed_packages
-            if package.provides(specification)
+            if package.satisfies(dependency, ignore_source_type=True)
         ]
         logger.debug(
             "Found <c2>%d</> compatible packages for <c2>%s</>",
             len(packages),
-            specification.complete_name,
+            dependency.complete_name,
         )
         return packages
 

tests/puzzle/test_solver.py

@@ -3648,3 +3648,36 @@ def test_solver_incompatible_dependency_with_and_without_extras(
             {"job": "install", "package": foo},
         ],
     )
+
+
+def test_update_with_prerelease_and_no_solution(
+    solver: Solver,
+    repo: Repository,
+    installed: InstalledRepository,
+    package: ProjectPackage,
+    locked: Repository,
+):
+    # Locked and installed: cleo which depends on an old version of crashtest.
+    cleo = get_package("cleo", "1.0.0a5")
+    crashtest = get_package("crashtest", "0.3.0")
+    cleo.add_dependency(Factory.create_dependency("crashtest", {"version": "<0.4.0"}))
+    locked.add_package(cleo)
+    locked.add_package(crashtest)
+
+    installed.add_package(cleo)
+    installed.add_package(crashtest)
+
+    # Try to upgrade to a new version of crashtest, this will be disallowed by the
+    # dependency from cleo.
+    package.add_dependency(Factory.create_dependency("cleo", "^1.0.0a5"))
+    package.add_dependency(Factory.create_dependency("crashtest", "^0.4.0"))
+
+    newer_crashtest = get_package("crashtest", "0.4.0")
+    even_newer_crashtest = get_package("crashtest", "0.4.1")
+    repo.add_package(cleo)
+    repo.add_package(crashtest)
+    repo.add_package(newer_crashtest)
+    repo.add_package(even_newer_crashtest)
+
+    with pytest.raises(SolverProblemError):
+        solver.solve()