getdeps: move the guts of _compute_env to a helper in buildopts

Summary: I want to use this logic outside of a builder implementation

Reviewed By: pkaush

Differential Revision: D16101914

fbshipit-source-id: db3c9ac6c84a92ab84a18dddb931953b0a51f127

build/fbcode_builder/getdeps/builder.py

@@ -86,39 +86,7 @@ class BuilderBase(object):
     def _compute_env(self, install_dirs):
         # CMAKE_PREFIX_PATH is only respected when passed through the
         # environment, so we construct an appropriate path to pass down
-        env = self.env.copy()
+        return self.build_opts.compute_env_for_install_dirs(install_dirs, env=self.env)
-
-        lib_path = None
-        if self.build_opts.is_darwin():
-            lib_path = "DYLD_LIBRARY_PATH"
-        elif self.build_opts.is_linux():
-            lib_path = "LD_LIBRARY_PATH"
-        else:
-            lib_path = None
-
-        for d in install_dirs:
-            add_path_entry(env, "CMAKE_PREFIX_PATH", d)
-
-            pkgconfig = os.path.join(d, "lib/pkgconfig")
-            if os.path.exists(pkgconfig):
-                add_path_entry(env, "PKG_CONFIG_PATH", pkgconfig)
-
-            # Allow resolving shared objects built earlier (eg: zstd
-            # doesn't include the full path to the dylib in its linkage
-            # so we need to give it an assist)
-            if lib_path:
-                for lib in ["lib", "lib64"]:
-                    libdir = os.path.join(d, lib)
-                    if os.path.exists(libdir):
-                        add_path_entry(env, lib_path, libdir)
-
-            # Allow resolving binaries (eg: cmake, ninja) and dlls
-            # built by earlier steps
-            bindir = os.path.join(d, "bin")
-            if os.path.exists(bindir):
-                add_path_entry(env, "PATH", bindir, append=False)
-
-        return env
 
 
 class MakeBuilder(BuilderBase):

build/fbcode_builder/getdeps/buildopts.py

@@ -16,7 +16,7 @@ import os
 import subprocess
 import tempfile
 
-from .envfuncs import path_search
+from .envfuncs import Env, add_path_entry, path_search
 from .platform import HostType, is_windows
 
 
@@ -190,6 +190,44 @@ class BuildOptions(object):
 
         return {"build_dir": build_dir, "inst_dir": inst_dir, "hash": hash}
 
+    def compute_env_for_install_dirs(self, install_dirs, env=None):
+        if env:
+            env = env.copy()
+        else:
+            env = Env()
+
+        lib_path = None
+        if self.is_darwin():
+            lib_path = "DYLD_LIBRARY_PATH"
+        elif self.is_linux():
+            lib_path = "LD_LIBRARY_PATH"
+        else:
+            lib_path = None
+
+        for d in install_dirs:
+            add_path_entry(env, "CMAKE_PREFIX_PATH", d)
+
+            pkgconfig = os.path.join(d, "lib/pkgconfig")
+            if os.path.exists(pkgconfig):
+                add_path_entry(env, "PKG_CONFIG_PATH", pkgconfig)
+
+            # Allow resolving shared objects built earlier (eg: zstd
+            # doesn't include the full path to the dylib in its linkage
+            # so we need to give it an assist)
+            if lib_path:
+                for lib in ["lib", "lib64"]:
+                    libdir = os.path.join(d, lib)
+                    if os.path.exists(libdir):
+                        add_path_entry(env, lib_path, libdir)
+
+            # Allow resolving binaries (eg: cmake, ninja) and dlls
+            # built by earlier steps
+            bindir = os.path.join(d, "bin")
+            if os.path.exists(bindir):
+                add_path_entry(env, "PATH", bindir, append=False)
+
+        return env
+
 
 def list_win32_subst_letters():
     output = subprocess.check_output(["subst"]).decode("utf-8")