fixes #20526; use nimPreviewSlimSystem for documentation build (#20714)

* fixes #20526; use `nimPreviewSlimSystem` for `koch docs`

* fixes documentation errors

* fixes remaning issues

lib/pure/asyncfile.nim

@@ -27,7 +27,7 @@ import asyncdispatch, os
 
 when defined(nimPreviewSlimSystem):
   import std/[assertions, syncio]
-  when defined(windows):
+  when defined(windows) or defined(nimdoc):
     import std/widestrs
 
 # TODO: Fix duplication introduced by PR #4683.

lib/pure/asyncftpclient.nim

@@ -84,6 +84,11 @@
 import asyncdispatch, asyncnet, nativesockets, strutils, parseutils, os, times
 from net import BufferSize, SslContext
 
+
+when defined(nimPreviewSlimSystem):
+  import std/syncio
+
+
 when defined(ssl):
   from net import SslHandshakeType, newContext, SslCVerifyMode
   var defaultSslContext {.threadvar.}: SslContext

lib/pure/coro.nim

@@ -33,6 +33,9 @@ import os
 import lists
 include system/timers
 
+when defined(nimPreviewSlimSystem):
+  import std/assertions
+
 const defaultStackSize = 512 * 1024
 const useOrcArc = defined(gcArc) or defined(gcOrc)
 

lib/pure/nimprof.nim

@@ -23,6 +23,9 @@ when defined(nimHasUsed):
 
 import hashes, algorithm, strutils, tables, sets
 
+when defined(nimPreviewSlimSystem):
+  import std/syncio
+
 when not defined(memProfiler):
   include "system/timers"
 

lib/pure/parsexml.nim

@@ -150,7 +150,7 @@ import
   strutils, lexbase, streams, unicode
 
 when defined(nimPreviewSlimSystem):
-  import std/assertions
+  import std/[assertions, syncio]
 
 # the parser treats ``<br />`` as ``<br></br>``
 

lib/pure/reservedmem.nim

@@ -20,6 +20,9 @@
 
 from std/oserrors import raiseOSError, osLastError
 
+when defined(nimPreviewSlimSystem):
+  import std/assertions
+
 template distance*(lhs, rhs: pointer): int =
   cast[int](rhs) - cast[int](lhs)
 

lib/pure/smtp.nim

@@ -46,6 +46,9 @@
 import net, strutils, strtabs, base64, os, strutils
 import asyncnet, asyncdispatch
 
+when defined(nimPreviewSlimSystem):
+  import std/assertions
+
 export Port
 
 type