fix #16025 repr now consistent: does not insert trailing newline (#16034)

3 files changed, 7 insertions, 2 deletions

diff --git a/lib/system.nim b/lib/system.nim
index 1104cb17f..716eb296a 100644
--- a/lib/system.nim
+++ b/lib/system.nim
@@ -1334,6 +1334,9 @@ proc insert*[T](x: var seq[T], item: sink T, i = 0.Natural) {.noSideEffect.} =
 when not defined(nimV2):
   proc repr*[T](x: T): string {.magic: "Repr", noSideEffect.}
     ## Takes any Nim variable and returns its string representation.
+    ## No trailing newline is inserted (so `echo` won't add an empty newline).
+    ## Use `-d:nimLegacyReprWithNewline` to revert to old behavior where newlines
+    ## were added in some cases.
     ##
     ## It works even for complex data graphs with cycles. This is a great
     ## debugging tool.
diff --git a/lib/system/repr.nim b/lib/system/repr.nim
index 318e95ebb..ae51a4aab 100644
--- a/lib/system/repr.nim
+++ b/lib/system/repr.nim
@@ -325,5 +325,6 @@ when not defined(useNimRtl):
     else:
       var p = p
       reprAux(result, addr(p), typ, cl)
-    add result, "\n"
+    when defined(nimLegacyReprWithNewline): # see PR #16034
+      add result, "\n"
     deinitReprClosure(cl)
diff --git a/lib/system/reprjs.nim b/lib/system/reprjs.nim
index 9c27a4721..36972024a 100644
--- a/lib/system/reprjs.nim
+++ b/lib/system/reprjs.nim
@@ -237,4 +237,5 @@ proc reprAny(p: pointer, typ: PNimType): string {.compilerRtl.} =
   var cl: ReprClosure
   initReprClosure(cl)
   reprAux(result, p, typ, cl)
-  add(result, "\n")
+  when defined(nimLegacyReprWithNewline): # see PR #16034
+    add result, "\n"