dep: support modifying category and package with Dep.modify()

src/pkgcraft/C.pxd

@@ -14,13 +14,15 @@ cdef extern from "pkgcraft.h":
         BLOCKER_WEAK,
 
     cdef enum:
-        DEP_FIELD_BLOCKER # = 1,
-        DEP_FIELD_VERSION # = (1 << 1),
-        DEP_FIELD_SLOT # = (1 << 2),
-        DEP_FIELD_SUBSLOT # = (1 << 3),
-        DEP_FIELD_SLOT_OP # = (1 << 4),
-        DEP_FIELD_USE_DEPS # = (1 << 5),
-        DEP_FIELD_REPO # = (1 << 6),
+        DEP_FIELD_CATEGORY # = 1,
+        DEP_FIELD_PACKAGE,
+        DEP_FIELD_BLOCKER,
+        DEP_FIELD_VERSION,
+        DEP_FIELD_SLOT,
+        DEP_FIELD_SUBSLOT,
+        DEP_FIELD_SLOT_OP,
+        DEP_FIELD_USE_DEPS,
+        DEP_FIELD_REPO,
     ctypedef uint32_t DepField
 
     # DepSet variants.
@@ -985,7 +987,9 @@ cdef extern from "pkgcraft.h":
     # The argument must be a non-null Dep pointer.
     Version *pkgcraft_dep_version(Dep *d)
 
-    # Return a package dependency without the specified fields
+    # Return a package dependency without the specified fields.
+    #
+    # Returns NULL on error.
     #
     # # Safety
     # The arguments must a valid Dep pointer and DepField values.

src/pkgcraft/dep/pkg.pyx

@@ -66,6 +66,8 @@ class SlotOperator(IntEnum):
 
 # mapping of field names to values for Dep.without()
 _DEP_FIELDS = MappingProxyType({
+    'category': C.DEP_FIELD_CATEGORY,
+    'package': C.DEP_FIELD_PACKAGE,
     'blocker': C.DEP_FIELD_BLOCKER,
     'version': C.DEP_FIELD_VERSION,
     'slot': C.DEP_FIELD_SLOT,
@@ -179,7 +181,9 @@ cdef class Dep:
             ptr = C.pkgcraft_dep_without(self.ptr, dep_fields, len(fields))
             PyMem_Free(dep_fields)
 
-            if ptr != self.ptr:
+            if ptr is NULL:
+                raise InvalidDep
+            elif ptr != self.ptr:
                 return Dep.from_ptr(ptr)
 
         return self

tests/dep/test_pkg.py

@@ -139,7 +139,7 @@ def test_valid(self):
                 Dep.valid(obj)
 
     def test_without(self):
-        fields = ("blocker", "version", "slot", "subslot", "slot_op", "use_deps", "repo")
+        optional_fields = ("blocker", "version", "slot", "subslot", "slot_op", "use_deps", "repo")
         dep = Dep("!!>=cat/pkg-1.2-r3:4/5=::repo[u]")
 
         # no args returns the same object
@@ -153,20 +153,26 @@ def test_without(self):
         assert str(dep.without("slot_op")) == "!!>=cat/pkg-1.2-r3:4/5::repo[u]"
         assert str(dep.without("use_deps")) == "!!>=cat/pkg-1.2-r3:4/5=::repo"
         assert str(dep.without("repo")) == "!!>=cat/pkg-1.2-r3:4/5=[u]"
-        assert str(dep.without(*fields)) == "cat/pkg"
+        assert str(dep.without(*optional_fields)) == "cat/pkg"
 
         # returns the same object when no fields are removed
         dep = Dep(">=cat/pkg-1.2-r3::repo")
         assert dep.without("use_deps") is dep
 
+        # category and package can't be unset
+        for field in ["category", "package"]:
+            with pytest.raises(InvalidDep):
+                dep.without(field)
+
         # invalid fields
         for obj in [object(), None, "field"]:
             with pytest.raises(ValueError):
                 dep.without(obj)
 
         # verify all combinations of dep fields create valid deps
         dep = Dep("!!>=cat/pkg-1.2-r3:4/5=::repo[a,b]")
-        for vals in chain.from_iterable(combinations(fields, r) for r in range(len(fields) + 1)):
+        lengths = range(len(optional_fields) + 1)
+        for vals in chain.from_iterable(combinations(optional_fields, r) for r in lengths):
             d = dep.without(*vals)
             assert d == Dep(str(d))
 
@@ -175,12 +181,27 @@ def test_modify(self):
         # no args returns the same object
         assert dep.modify() is dep
 
+        # category
+        dep = Dep("cat/pkg")
+        dep = dep.modify(category="a")
+        assert str(dep) == "a/pkg"
+        with pytest.raises(InvalidDep):
+            dep.modify(category=None)
+
+        # package
+        dep = Dep("cat/pkg")
+        dep = dep.modify(package="b")
+        assert str(dep) == "cat/b"
+        with pytest.raises(InvalidDep):
+            dep.modify(package=None)
+
         # version
         dep = Dep("cat/pkg")
         dep = dep.modify(version=">1")
         assert str(dep) == ">cat/pkg-1"
         dep = dep.modify(version=None)
         assert str(dep) == "cat/pkg"
+        assert dep.modify(version=None) is dep
 
         # invalid version values
         for s in ("", "1.2.3-r4"):