linkers: delay implementations import until detect is run

This saves on a 1500-line import at startup and may be skipped entirely
if no compiled languages are used. In exchange, we move the
implementation to a new file that is imported instead.

Followup to commit ab20eb5bbc21ae855bcd211131132d2778602bcf.

4 files changed, 77 insertions, 185 deletions

diff --git a/mesonbuild/linkers/__init__.py b/mesonbuild/linkers/__init__.py
index b9df8d7..7c35694 100644
--- a/mesonbuild/linkers/__init__.py
+++ b/mesonbuild/linkers/__init__.py
@@ -12,139 +12,21 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+
+from .base import ArLikeLinker, RSPFileSyntax
 from .detect import (
     defaults,
     guess_win_linker,
     guess_nix_linker,
 )
-from .linkers import (
-    RSPFileSyntax,
-
-    StaticLinker,
-    VisualStudioLikeLinker,
-    VisualStudioLinker,
-    IntelVisualStudioLinker,
-    AppleArLinker,
-    ArLikeLinker,
-    ArLinker,
-    ArmarLinker,
-    DLinker,
-    CcrxLinker,
-    Xc16Linker,
-    CompCertLinker,
-    C2000Linker,
-    TILinker,
-    AIXArLinker,
-    PGIStaticLinker,
-    NvidiaHPC_StaticLinker,
-    MetrowerksStaticLinker,
-    MetrowerksStaticLinkerARM,
-    MetrowerksStaticLinkerEmbeddedPowerPC,
-
-    DynamicLinker,
-    PosixDynamicLinkerMixin,
-    GnuLikeDynamicLinkerMixin,
-    AppleDynamicLinker,
-    GnuDynamicLinker,
-    GnuGoldDynamicLinker,
-    GnuBFDDynamicLinker,
-    LLVMDynamicLinker,
-    MoldDynamicLinker,
-    WASMDynamicLinker,
-    CcrxDynamicLinker,
-    Xc16DynamicLinker,
-    CompCertDynamicLinker,
-    C2000DynamicLinker,
-    TIDynamicLinker,
-    ArmDynamicLinker,
-    ArmClangDynamicLinker,
-    QualcommLLVMDynamicLinker,
-    PGIDynamicLinker,
-    NvidiaHPC_DynamicLinker,
-    NAGDynamicLinker,
-    MetrowerksLinker,
-    MetrowerksLinkerARM,
-    MetrowerksLinkerEmbeddedPowerPC,
-
-    VisualStudioLikeLinkerMixin,
-    MSVCDynamicLinker,
-    ClangClDynamicLinker,
-    XilinkDynamicLinker,
-    SolarisDynamicLinker,
-    AIXDynamicLinker,
-    OptlinkDynamicLinker,
-    CudaLinker,
-
-    prepare_rpaths,
-    order_rpaths,
-    evaluate_rpath,
-)
 
 __all__ = [
+    # base.py
+    'ArLikeLinker',
+    'RSPFileSyntax',
+
     # detect.py
     'defaults',
     'guess_win_linker',
     'guess_nix_linker',
-
-    # linkers.py
-    'RSPFileSyntax',
-
-    'StaticLinker',
-    'VisualStudioLikeLinker',
-    'VisualStudioLinker',
-    'IntelVisualStudioLinker',
-    'ArLikeLinker',
-    'ArLinker',
-    'ArmarLinker',
-    'DLinker',
-    'CcrxLinker',
-    'Xc16Linker',
-    'CompCertLinker',
-    'C2000Linker',
-    'TILinker',
-    'AIXArLinker',
-    'AppleArLinker',
-    'PGIStaticLinker',
-    'NvidiaHPC_StaticLinker',
-    'MetrowerksStaticLinker',
-    'MetrowerksStaticLinkerARM',
-    'MetrowerksStaticLinkerEmbeddedPowerPC',
-
-    'DynamicLinker',
-    'PosixDynamicLinkerMixin',
-    'GnuLikeDynamicLinkerMixin',
-    'AppleDynamicLinker',
-    'GnuDynamicLinker',
-    'GnuGoldDynamicLinker',
-    'GnuBFDDynamicLinker',
-    'LLVMDynamicLinker',
-    'MoldDynamicLinker',
-    'WASMDynamicLinker',
-    'CcrxDynamicLinker',
-    'Xc16DynamicLinker',
-    'CompCertDynamicLinker',
-    'C2000DynamicLinker',
-    'TIDynamicLinker',
-    'ArmDynamicLinker',
-    'ArmClangDynamicLinker',
-    'QualcommLLVMDynamicLinker',
-    'PGIDynamicLinker',
-    'NvidiaHPC_DynamicLinker',
-    'NAGDynamicLinker',
-    'MetrowerksLinker',
-    'MetrowerksLinkerARM',
-    'MetrowerksLinkerEmbeddedPowerPC',
-
-    'VisualStudioLikeLinkerMixin',
-    'MSVCDynamicLinker',
-    'ClangClDynamicLinker',
-    'XilinkDynamicLinker',
-    'SolarisDynamicLinker',
-    'AIXDynamicLinker',
-    'OptlinkDynamicLinker',
-    'CudaLinker',
-
-    'prepare_rpaths',
-    'order_rpaths',
-    'evaluate_rpath',
 ]
diff --git a/mesonbuild/linkers/base.py b/mesonbuild/linkers/base.py
new file mode 100644
index 0000000..a656bb4
--- /dev/null
+++ b/mesonbuild/linkers/base.py
@@ -0,0 +1,50 @@
+# Copyright 2012-2023 The Meson development team
+
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+
+#     https://www.apache.org/licenses/LICENSE-2.0
+
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# Core public classes for linkers.
+from __future__ import annotations
+
+import enum
+import typing as T
+
+if T.TYPE_CHECKING:
+    from ..environment import Environment
+
+
+@enum.unique
+class RSPFileSyntax(enum.Enum):
+
+    """Which RSP file syntax the compiler supports."""
+
+    MSVC = enum.auto()
+    GCC = enum.auto()
+
+
+class ArLikeLinker:
+    # POSIX requires supporting the dash, GNU permits omitting it
+    std_args = ['-csr']
+
+    def can_linker_accept_rsp(self) -> bool:
+        # armar / AIX can't accept arguments using the @rsp syntax
+        # in fact, only the 'ar' id can
+        return False
+
+    def get_std_link_args(self, env: 'Environment', is_thin: bool) -> T.List[str]:
+        return self.std_args
+
+    def get_output_args(self, target: str) -> T.List[str]:
+        return [target]
+
+    def rsp_file_syntax(self) -> RSPFileSyntax:
+        return RSPFileSyntax.GCC
diff --git a/mesonbuild/linkers/detect.py b/mesonbuild/linkers/detect.py
index 3f8de05..60be10f 100644
--- a/mesonbuild/linkers/detect.py
+++ b/mesonbuild/linkers/detect.py
@@ -19,20 +19,6 @@ from ..mesonlib import (
     EnvironmentException,
     Popen_safe, Popen_safe_logged, join_args, search_version
 )
-from .linkers import (
-    AppleDynamicLinker,
-    LLVMLD64DynamicLinker,
-    GnuGoldDynamicLinker,
-    GnuBFDDynamicLinker,
-    MoldDynamicLinker,
-    LLVMDynamicLinker,
-    QualcommLLVMDynamicLinker,
-    MSVCDynamicLinker,
-    ClangClDynamicLinker,
-    SolarisDynamicLinker,
-    AIXDynamicLinker,
-    OptlinkDynamicLinker,
-)
 
 import re
 import shlex
@@ -62,6 +48,7 @@ def guess_win_linker(env: 'Environment', compiler: T.List[str], comp_class: T.Ty
                      comp_version: str, for_machine: MachineChoice, *,
                      use_linker_prefix: bool = True, invoked_directly: bool = True,
                      extra_args: T.Optional[T.List[str]] = None) -> 'DynamicLinker':
+    from . import linkers
     env.coredata.add_lang_args(comp_class.language, comp_class, for_machine, env)
 
     # Explicitly pass logo here so that we can get the version of link.exe
@@ -86,11 +73,11 @@ def guess_win_linker(env: 'Environment', compiler: T.List[str], comp_class: T.Ty
     p, o, _ = Popen_safe(compiler + check_args)
     if 'LLD' in o.split('\n', maxsplit=1)[0]:
         if '(compatible with GNU linkers)' in o:
-            return LLVMDynamicLinker(
+            return linkers.LLVMDynamicLinker(
                 compiler, for_machine, comp_class.LINKER_PREFIX,
                 override, version=search_version(o))
         elif not invoked_directly:
-            return ClangClDynamicLinker(
+            return linkers.ClangClDynamicLinker(
                 for_machine, override, exelist=compiler, prefix=comp_class.LINKER_PREFIX,
                 version=search_version(o), direct=False, machine=None)
 
@@ -100,13 +87,13 @@ def guess_win_linker(env: 'Environment', compiler: T.List[str], comp_class: T.Ty
 
     p, o, e = Popen_safe(compiler + check_args)
     if 'LLD' in o.split('\n', maxsplit=1)[0]:
-        return ClangClDynamicLinker(
+        return linkers.ClangClDynamicLinker(
             for_machine, [],
             prefix=comp_class.LINKER_PREFIX if use_linker_prefix else [],
             exelist=compiler, version=search_version(o), direct=invoked_directly)
     elif 'OPTLINK' in o:
         # Optlink's stdout *may* begin with a \r character.
-        return OptlinkDynamicLinker(compiler, for_machine, version=search_version(o))
+        return linkers.OptlinkDynamicLinker(compiler, for_machine, version=search_version(o))
     elif o.startswith('Microsoft') or e.startswith('Microsoft'):
         out = o or e
         match = re.search(r'.*(X86|X64|ARM|ARM64).*', out)
@@ -115,7 +102,7 @@ def guess_win_linker(env: 'Environment', compiler: T.List[str], comp_class: T.Ty
         else:
             target = 'x86'
 
-        return MSVCDynamicLinker(
+        return linkers.MSVCDynamicLinker(
             for_machine, [], machine=target, exelist=compiler,
             prefix=comp_class.LINKER_PREFIX if use_linker_prefix else [],
             version=search_version(out), direct=invoked_directly)
@@ -139,6 +126,7 @@ def guess_nix_linker(env: 'Environment', compiler: T.List[str], comp_class: T.Ty
     :for_machine: which machine this linker targets
     :extra_args: Any additional arguments required (such as a source file)
     """
+    from . import linkers
     env.coredata.add_lang_args(comp_class.language, comp_class, for_machine, env)
     extra_args = extra_args or []
 
@@ -170,14 +158,14 @@ def guess_nix_linker(env: 'Environment', compiler: T.List[str], comp_class: T.Ty
 
         lld_cls: T.Type[DynamicLinker]
         if 'ld64.lld' in newerr:
-            lld_cls = LLVMLD64DynamicLinker
+            lld_cls = linkers.LLVMLD64DynamicLinker
         else:
-            lld_cls = LLVMDynamicLinker
+            lld_cls = linkers.LLVMDynamicLinker
 
         linker = lld_cls(
             compiler, for_machine, comp_class.LINKER_PREFIX, override, version=v)
     elif 'Snapdragon' in e and 'LLVM' in e:
-        linker = QualcommLLVMDynamicLinker(
+        linker = linkers.QualcommLLVMDynamicLinker(
             compiler, for_machine, comp_class.LINKER_PREFIX, override, version=v)
     elif e.startswith('lld-link: '):
         # The LLD MinGW frontend didn't respond to --version before version 9.0.0,
@@ -196,7 +184,7 @@ def guess_nix_linker(env: 'Environment', compiler: T.List[str], comp_class: T.Ty
             _, o, e = Popen_safe([linker_cmd, '--version'])
             v = search_version(o)
 
-        linker = LLVMDynamicLinker(compiler, for_machine, comp_class.LINKER_PREFIX, override, version=v)
+        linker = linkers.LLVMDynamicLinker(compiler, for_machine, comp_class.LINKER_PREFIX, override, version=v)
     # first might be apple clang, second is for real gcc, the third is icc
     elif e.endswith('(use -v to see invocation)\n') or 'macosx_version' in e or 'ld: unknown option:' in e:
         if isinstance(comp_class.LINKER_PREFIX, str):
@@ -211,17 +199,17 @@ def guess_nix_linker(env: 'Environment', compiler: T.List[str], comp_class: T.Ty
                 break
         else:
             __failed_to_detect_linker(compiler, check_args, o, e)
-        linker = AppleDynamicLinker(compiler, for_machine, comp_class.LINKER_PREFIX, override, version=v)
+        linker = linkers.AppleDynamicLinker(compiler, for_machine, comp_class.LINKER_PREFIX, override, version=v)
     elif 'GNU' in o or 'GNU' in e:
         gnu_cls: T.Type[GnuDynamicLinker]
         # this is always the only thing on stdout, except for swift
         # which may or may not redirect the linker stdout to stderr
         if o.startswith('GNU gold') or e.startswith('GNU gold'):
-            gnu_cls = GnuGoldDynamicLinker
+            gnu_cls = linkers.GnuGoldDynamicLinker
         elif o.startswith('mold') or e.startswith('mold'):
-            gnu_cls = MoldDynamicLinker
+            gnu_cls = linkers.MoldDynamicLinker
         else:
-            gnu_cls = GnuBFDDynamicLinker
+            gnu_cls = linkers.GnuBFDDynamicLinker
         linker = gnu_cls(compiler, for_machine, comp_class.LINKER_PREFIX, override, version=v)
     elif 'Solaris' in e or 'Solaris' in o:
         for line in (o+e).split('\n'):
@@ -230,7 +218,7 @@ def guess_nix_linker(env: 'Environment', compiler: T.List[str], comp_class: T.Ty
                 break
         else:
             v = 'unknown version'
-        linker = SolarisDynamicLinker(
+        linker = linkers.SolarisDynamicLinker(
             compiler, for_machine, comp_class.LINKER_PREFIX, override,
             version=v)
     elif 'ld: 0706-012 The -- flag is not recognized' in e:
@@ -238,7 +226,7 @@ def guess_nix_linker(env: 'Environment', compiler: T.List[str], comp_class: T.Ty
             _, _, e = Popen_safe(compiler + [comp_class.LINKER_PREFIX + '-V'] + extra_args)
         else:
             _, _, e = Popen_safe(compiler + comp_class.LINKER_PREFIX + ['-V'] + extra_args)
-        linker = AIXDynamicLinker(
+        linker = linkers.AIXDynamicLinker(
             compiler, for_machine, comp_class.LINKER_PREFIX, override,
             version=search_version(e))
     else:
diff --git a/mesonbuild/linkers/linkers.py b/mesonbuild/linkers/linkers.py
index 21e0eeb..d7868f2 100644
--- a/mesonbuild/linkers/linkers.py
+++ b/mesonbuild/linkers/linkers.py
@@ -14,10 +14,10 @@
 from __future__ import annotations
 
 import abc
-import enum
 import os
 import typing as T
 
+from .base import ArLikeLinker, RSPFileSyntax
 from .. import mesonlib
 from ..mesonlib import EnvironmentException, MesonException
 from ..arglist import CompilerArgs
@@ -28,15 +28,6 @@ if T.TYPE_CHECKING:
     from ..mesonlib import MachineChoice
 
 
-@enum.unique
-class RSPFileSyntax(enum.Enum):
-
-    """Which RSP file syntax the compiler supports."""
-
-    MSVC = enum.auto()
-    GCC = enum.auto()
-
-
 class StaticLinker:
 
     id: str
@@ -168,26 +159,7 @@ class IntelVisualStudioLinker(VisualStudioLikeLinker, StaticLinker):
         VisualStudioLikeLinker.__init__(self, machine)
 
 
-class ArLikeLinker(StaticLinker):
-    # POSIX requires supporting the dash, GNU permits omitting it
-    std_args = ['-csr']
-
-    def can_linker_accept_rsp(self) -> bool:
-        # armar / AIX can't accept arguments using the @rsp syntax
-        # in fact, only the 'ar' id can
-        return False
-
-    def get_std_link_args(self, env: 'Environment', is_thin: bool) -> T.List[str]:
-        return self.std_args
-
-    def get_output_args(self, target: str) -> T.List[str]:
-        return [target]
-
-    def rsp_file_syntax(self) -> RSPFileSyntax:
-        return RSPFileSyntax.GCC
-
-
-class ArLinker(ArLikeLinker):
+class ArLinker(ArLikeLinker, StaticLinker):
     id = 'ar'
 
     def __init__(self, for_machine: mesonlib.MachineChoice, exelist: T.List[str]):
@@ -227,7 +199,7 @@ class AppleArLinker(ArLinker):
     id = 'applear'
 
 
-class ArmarLinker(ArLikeLinker):
+class ArmarLinker(ArLikeLinker, StaticLinker):
     id = 'armar'
 
 
@@ -322,7 +294,7 @@ class C2000Linker(TILinker):
     id = 'ar2000'
 
 
-class AIXArLinker(ArLikeLinker):
+class AIXArLinker(ArLikeLinker, StaticLinker):
     id = 'aixar'
     std_args = ['-csr', '-Xany']