From ab3ab545be0b550cca1c2529f7e97fbebf5eba81 Mon Sep 17 00:00:00 2001
From: andri lim <jangko128@gmail.com>
Date: Fri, 16 Feb 2024 11:34:42 +0700
Subject: [PATCH] =?UTF-8?q?Silence=20declared=20but=20unused=20warnings=20?=
 =?UTF-8?q?when=20there=20is=20no=20loggging=20code=20g=E2=80=A6=20(#143)?=
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* Silence declared but unused warnings when there is no loggging code generated

* Create custom 'used' magic

* Also disable warning for eventName
---
 chronicles.nim | 23 +++++++++++++++++++----
 1 file changed, 19 insertions(+), 4 deletions(-)

diff --git a/chronicles.nim b/chronicles.nim
index 95e283a..7b184e3 100644
--- a/chronicles.nim
+++ b/chronicles.nim
@@ -159,13 +159,13 @@ else:
   else:
     proc getLogThreadId*(): int = 0
 
-template formatItIMPL*(value: any): auto =
+template formatItIMPL*(value: auto): auto =
   value
 
 template formatIt*(T: type, body: untyped) {.dirty.} =
   template formatItIMPL*(it: T): auto = body
 
-template expandItIMPL*[R](record: R, field: static string, value: any) =
+template expandItIMPL*[R](record: R, field: static string, value: auto) =
   mixin setProperty, formatItIMPL
   setProperty(record, field, formatItIMPL(value))
 
@@ -216,6 +216,11 @@ macro expandIt*(T: type, expandedProps: untyped): untyped =
   when defined(debugLogImpl):
     echo result.repr
 
+template chroniclesUsedMagic(x: untyped) =
+  # Force the compiler to mark any symbol in the x
+  # as used without actually generate any code.
+  when compiles(x): discard
+
 macro logIMPL(lineInfo: static InstInfo,
               Stream: typed,
               RecordType: type,
@@ -223,7 +228,6 @@ macro logIMPL(lineInfo: static InstInfo,
               severity: static[LogLevel],
               scopes: typed,
               logStmtBindings: varargs[untyped]): untyped =
-  if not loggingEnabled: return
   clearEmptyVarargs logStmtBindings
 
   # First, we merge the lexical bindings with the additional
@@ -237,6 +241,17 @@ macro logIMPL(lineInfo: static InstInfo,
   for k, v in assignments(lexicalBindings, acLogStatement):
     finalBindings[k] = v
 
+  result = newStmtList()
+  # This statement is to silence compiler warnings
+  # `declared but not used` when there is no logging code generated.
+  # push/pop pragma pairs cannot be used in this situation
+  # because the variables are declared outside of this function.
+  result.add quote do: chroniclesUsedMagic(`eventName`)
+  for k, v in finalBindings:
+    result.add quote do: chroniclesUsedMagic(`v`)
+
+  if not loggingEnabled: return
+
   # This is the compile-time topic filtering code, which has a similar
   # logic to the generated run-time filtering code:
   var enabledTopicsMatch = enabledTopics.len == 0 and severity >= enabledLogLevel
@@ -314,7 +329,7 @@ macro logIMPL(lineInfo: static InstInfo,
   code.add newCall("logAllDynamicProperties", Stream, record)
   code.add newCall("flushRecord", record)
 
-  result = quote do:
+  result.add quote do:
     try:
       block `chroniclesBlockName`:
         `code`