tree-wide: reduce unneeded imports on specific Dependency impls

We can check something's subtype using properties, without importing the
module up front and doing isinstance checks on specific subclasses of
the interface -- or worse, solving cyclic imports by doing the import
inside the function. ;)

4 files changed, 12 insertions, 13 deletions

diff --git a/mesonbuild/backend/backends.py b/mesonbuild/backend/backends.py
index a13c0ec..14f03b1 100644
--- a/mesonbuild/backend/backends.py
+++ b/mesonbuild/backend/backends.py
@@ -740,7 +740,7 @@ class Backend:
         srcdir = self.environment.get_source_dir()
 
         for dep in target.external_deps:
-            if not isinstance(dep, (dependencies.ExternalLibrary, dependencies.PkgConfigDependency)):
+            if dep.type_name not in {'library', 'pkgconfig'}:
                 continue
             for libpath in dep.link_args:
                 # For all link args that are absolute paths to a library file, add RPATH args
@@ -1006,7 +1006,8 @@ class Backend:
                 continue
 
             if compiler.language == 'vala':
-                if isinstance(dep, dependencies.PkgConfigDependency):
+                if dep.type_name == 'pkgconfig':
+                    assert isinstance(dep, dependencies.ExternalDependency)
                     if dep.name == 'glib-2.0' and dep.version_reqs is not None:
                         for req in dep.version_reqs:
                             if req.startswith(('>=', '==')):
@@ -1075,7 +1076,7 @@ class Backend:
         results = set()
         for dep in target.external_deps:
 
-            if isinstance(dep, dependencies.PkgConfigDependency):
+            if dep.type_name == 'pkgconfig':
                 # If by chance pkg-config knows the bin dir...
                 bindir = dep.get_pkgconfig_variable('bindir', [], default='')
                 if bindir:
diff --git a/mesonbuild/backend/vs2010backend.py b/mesonbuild/backend/vs2010backend.py
index de6d8d7..d6b2f44 100644
--- a/mesonbuild/backend/vs2010backend.py
+++ b/mesonbuild/backend/vs2010backend.py
@@ -25,7 +25,6 @@ import re
 
 from . import backends
 from .. import build
-from .. import dependencies
 from .. import mlog
 from .. import compilers
 from ..mesonlib import (
@@ -944,6 +943,7 @@ class Vs2010Backend(backends.Backend):
             return self.gen_compile_target_vcxproj(target, ofname, guid)
         else:
             raise MesonException(f'Unknown target type for {target.get_basename()}')
+        assert isinstance(target, (build.Executable, build.SharedLibrary, build.StaticLibrary, build.SharedModule)), 'for mypy'
         # Prefix to use to access the build root from the vcxproj dir
         down = self.target_to_build_root(target)
         # Prefix to use to access the source tree's root from the vcxproj dir
@@ -1175,7 +1175,7 @@ class Vs2010Backend(backends.Backend):
         for d in reversed(target.get_external_deps()):
             # Cflags required by external deps might have UNIX-specific flags,
             # so filter them out if needed
-            if isinstance(d, dependencies.OpenMPDependency):
+            if d.name == 'openmp':
                 ET.SubElement(clconf, 'OpenMPSupport').text = 'true'
             else:
                 d_compile_args = compiler.unix_args_to_native(d.get_compile_args())
@@ -1288,14 +1288,14 @@ class Vs2010Backend(backends.Backend):
             for dep in target.get_external_deps():
                 # Extend without reordering or de-dup to preserve `-L -l` sets
                 # https://github.com/mesonbuild/meson/issues/1718
-                if isinstance(dep, dependencies.OpenMPDependency):
+                if dep.name == 'openmp':
                     ET.SubElement(clconf, 'OpenMPSupport').text = 'true'
                 else:
                     extra_link_args.extend_direct(dep.get_link_args())
             for d in target.get_dependencies():
                 if isinstance(d, build.StaticLibrary):
                     for dep in d.get_external_deps():
-                        if isinstance(dep, dependencies.OpenMPDependency):
+                        if dep.name == 'openmp':
                             ET.SubElement(clconf, 'OpenMPSupport').text = 'true'
                         else:
                             extra_link_args.extend_direct(dep.get_link_args())
diff --git a/mesonbuild/coredata.py b/mesonbuild/coredata.py
index 46127c6..27b1b91 100644
--- a/mesonbuild/coredata.py
+++ b/mesonbuild/coredata.py
@@ -324,11 +324,10 @@ class DependencyCacheType(enum.Enum):
 
     @classmethod
     def from_type(cls, dep: 'dependencies.Dependency') -> 'DependencyCacheType':
-        from . import dependencies
         # As more types gain search overrides they'll need to be added here
-        if isinstance(dep, dependencies.PkgConfigDependency):
+        if dep.type_name == 'pkgconfig':
             return cls.PKG_CONFIG
-        if isinstance(dep, dependencies.CMakeDependency):
+        if dep.type_name == 'cmake':
             return cls.CMAKE
         return cls.OTHER
 
diff --git a/mesonbuild/modules/pkgconfig.py b/mesonbuild/modules/pkgconfig.py
index 714955d..921fb66 100644
--- a/mesonbuild/modules/pkgconfig.py
+++ b/mesonbuild/modules/pkgconfig.py
@@ -26,7 +26,6 @@ from .. import dependencies
 from .. import mesonlib
 from .. import mlog
 from ..coredata import BUILTIN_DIR_OPTIONS
-from ..dependencies import ThreadDependency
 from ..dependencies.pkgconfig import PkgConfigDependency
 from ..interpreter.type_checking import D_MODULE_VERSIONS_KW, INSTALL_DIR_KW, VARIABLES_KW, NoneType
 from ..interpreterbase import FeatureNew, FeatureDeprecated
@@ -164,7 +163,7 @@ class DependenciesHelper:
                 self.add_version_reqs(name, [version_req] if version_req is not None else None)
             elif isinstance(obj, dependencies.Dependency) and not obj.found():
                 pass
-            elif isinstance(obj, ThreadDependency):
+            elif isinstance(obj, dependencies.ExternalDependency) and obj.name == 'threads':
                 pass
             else:
                 raise mesonlib.MesonException('requires argument not a string, '
@@ -196,7 +195,7 @@ class DependenciesHelper:
                     and obj.get_id() in self.metadata):
                 self._check_generated_pc_deprecation(obj)
                 processed_reqs.append(self.metadata[obj.get_id()].filebase)
-            elif isinstance(obj, dependencies.ValgrindDependency):
+            elif isinstance(obj, dependencies.ExternalDependency) and obj.name == 'valgrind':
                 pass
             elif isinstance(obj, PkgConfigDependency):
                 if obj.found():