Prevent solver from selecting packages with empty markers

poetry/puzzle/solver.py

@@ -184,6 +184,7 @@ class Solver:
         graph = self._build_graph(self._package, packages)
         graph = self._build_graph(self._package, packages)
 
 
         depths = []
         depths = []
+        final_packages = []
         for package in packages:
         for package in packages:
             category, optional, marker, depth = self._get_tags_for_package(
             category, optional, marker, depth = self._get_tags_for_package(
                 package, graph
                 package, graph
@@ -191,14 +192,17 @@ class Solver:
 
 
             if marker is None:
             if marker is None:
                 marker = AnyMarker()
                 marker = AnyMarker()
+            if marker.is_empty():
+                continue
 
 
             package.category = category
             package.category = category
             package.optional = optional
             package.optional = optional
             package.marker = marker
             package.marker = marker
 
 
             depths.append(depth)
             depths.append(depth)
+            final_packages.append(package)
 
 
-        return packages, depths
+        return final_packages, depths
 
 
     def _build_graph(
     def _build_graph(
         self, package, packages, previous=None, previous_dep=None, dep=None
         self, package, packages, previous=None, previous_dep=None, dep=None

tests/puzzle/test_solver.py

@@ -1743,3 +1743,35 @@ def test_solver_chooses_from_secondary_if_explicit(package, installed, locked, i
     assert "" == ops[1].package.source_url
     assert "" == ops[1].package.source_url
     assert "" == ops[2].package.source_type
     assert "" == ops[2].package.source_type
     assert "" == ops[2].package.source_url
     assert "" == ops[2].package.source_url
+
+
+def test_solver_discards_packages_with_empty_markers(
+    package, installed, locked, io, pool, repo
+):
+    package.python_versions = "~2.7 || ^3.4"
+    package.add_dependency(
+        "a", {"version": "^0.1.0", "markers": "python_version >= '3.4'"}
+    )
+
+    package_a = get_package("a", "0.1.0")
+    package_a.add_dependency(
+        "b", {"version": "^0.1.0", "markers": "python_version < '3.2'"}
+    )
+    package_a.add_dependency("c", "^0.2.0")
+    package_b = get_package("b", "0.1.0")
+    package_c = get_package("c", "0.2.0")
+    repo.add_package(package_a)
+    repo.add_package(package_b)
+    repo.add_package(package_c)
+
+    solver = Solver(package, pool, installed, locked, io)
+
+    ops = solver.solve()
+
+    check_solver_result(
+        ops,
+        [
+            {"job": "install", "package": package_c},
+            {"job": "install", "package": package_a},
+        ],
+    )