refactor os imports into corresponding small modules (#20720)

compiler/vmops.nim

@@ -24,8 +24,9 @@ when declared(math.signbit):
 
 
 from std/envvars import getEnv, existsEnv, delEnv, putEnv, envPairs
-from std/os import walkDir, getAppFilename
+from std/os import getAppFilename
 from std/private/oscommon import dirExists, fileExists
+from std/private/osdirs import walkDir
 
 from std/times import cpuTime
 from std/hashes import hash

lib/pure/distros.nim

@@ -31,7 +31,7 @@ from std/strutils import contains, toLowerAscii
 
 when not defined(nimscript):
   from std/osproc import execProcess
-  from std/os import existsEnv
+  from std/envvars import existsEnv
 
 type
   Distribution* {.pure.} = enum ## the list of known distributions

lib/pure/memfiles.nim

@@ -24,7 +24,8 @@ elif defined(posix):
 else:
   {.error: "the memfiles module is not supported on your operating system!".}
 
-import os, streams
+import streams
+import std/oserrors
 
 when defined(nimPreviewSlimSystem):
   import std/[syncio, assertions]

lib/pure/reservedmem.nim

@@ -18,7 +18,7 @@
 ##
 ## Unstable API.
 
-from os import raiseOSError, osLastError
+from std/oserrors import raiseOSError, osLastError
 
 template distance*(lhs, rhs: pointer): int =
   cast[int](rhs) - cast[int](lhs)

lib/pure/selectors.nim

@@ -27,7 +27,8 @@
 ##
 ## TODO: `/dev/poll`, `event ports` and filesystem events.
 
-import os, nativesockets
+import nativesockets
+import std/oserrors
 
 when defined(nimPreviewSlimSystem):
   import std/assertions

lib/pure/strtabs.nim

@@ -61,7 +61,7 @@ when defined(js) or defined(nimscript) or defined(Standalone):
   {.pragma: rtlFunc.}
 else:
   {.pragma: rtlFunc, rtl.}
-  import os
+  import std/envvars
 
 include "system/inclrtl"
 

lib/std/sysrand.nim

@@ -57,7 +57,7 @@ runnableExamples:
 
 
 when not defined(js):
-  import os
+  import std/oserrors
 
 when defined(posix):
   import posix

lib/windows/registry.nim

@@ -9,7 +9,7 @@
 
 ## This module is experimental and its interface may change.
 
-import winlean, os
+import std/oserrors
 
 when defined(nimPreviewSlimSystem):
   import std/widestrs