From b2bf70eacebbf4ce11fae0bb1fa680c22be2c69e Mon Sep 17 00:00:00 2001
From: Calvin Rose <calsrose@gmail.com>
Date: Wed, 4 Feb 2026 18:52:20 -0600
Subject: [PATCH] Move peg debug output to stderr in line with other internal
 debug tools.

Also allow disabling color in the debug output.
---
 src/core/capi.c      |  2 +-
 src/core/peg.c       | 10 ++++++++--
 test/suite-peg.janet | 34 ++++++++++++++++++++--------------
 3 files changed, 29 insertions(+), 17 deletions(-)

diff --git a/src/core/capi.c b/src/core/capi.c
index 526e58a8..7981a6eb 100644
--- a/src/core/capi.c
+++ b/src/core/capi.c
@@ -460,7 +460,7 @@ Janet janet_dyn(const char *name) {
         return janet_table_get(janet_vm.top_dyns, janet_ckeywordv(name));
     }
     if (janet_vm.fiber->env) {
-        return janet_table_get(janet_vm.fiber->env, janet_ckeywordv(name));
+        return janet_table_get_keyword(janet_vm.fiber->env, name);
     } else {
         return janet_wrap_nil();
     }
diff --git a/src/core/peg.c b/src/core/peg.c
index 1912dcea..bddb87a4 100644
--- a/src/core/peg.c
+++ b/src/core/peg.c
@@ -198,10 +198,16 @@ tail:
             char buffer[32] = {0};
             size_t len = (size_t)(s->outer_text_end - text);
             memcpy(buffer, text, (len > 31 ? 31 : len));
-            janet_printf("\n?? at [%s]\nstack [%d]:\n", buffer, s->captures->count);
+            janet_eprintf("\n?? at [%s]\nstack [%d]:\n", buffer, s->captures->count);
+            int has_color = janet_truthy(janet_dyn("err-color"));
             for (int32_t i = 0; i < s->captures->count; i++) {
-                janet_printf("  [%d]: %M\n", i, s->captures->data[i]);
+                if (has_color) {
+                    janet_eprintf("  [%d]: %M\n", i, s->captures->data[i]);
+                } else {
+                    janet_eprintf("  [%d]: %m\n", i, s->captures->data[i]);
+                }
             }
+            janet_eprintf("\n");
             return text;
         }
 
diff --git a/test/suite-peg.janet b/test/suite-peg.janet
index ae3d0dbf..9684d63b 100644
--- a/test/suite-peg.janet
+++ b/test/suite-peg.janet
@@ -266,6 +266,12 @@
 (marshpeg '(sub "abcdf" "abc"))
 (marshpeg '(* (sub 1 1)))
 (marshpeg '(split "," (+ "a" "b" "c")))
+(marshpeg "")
+(marshpeg 1)
+(marshpeg 0)
+(marshpeg -1)
+(marshpeg '(drop 1))
+(marshpeg '(accumulate 1))
 
 # Peg swallowing errors
 # 159651117
@@ -846,49 +852,49 @@
       @[["b" "b" "b"]])
 
 # Debug and ?? tests.
-(defn test-stdout [name peg input expected-matches expected-stdout]
+(defn test-stderr [name peg input expected-matches expected-stdout]
   (def actual @"")
-  (with-dyns [:out actual]
+  (with-dyns [:err actual]
     (test name peg input expected-matches))
   (assert (deep= (string actual) expected-stdout)))
 
-(test-stdout "?? long form"
+(test-stderr "?? long form"
   '(* (debug) "abc")
   "abc"
   @[]
-  "\n?? at [abc]\nstack [0]:\n")
+  "\n?? at [abc]\nstack [0]:\n\n")
 
-(test-stdout "?? short form"
+(test-stderr "?? short form"
   '(* (??) "abc")
   "abc"
   @[]
-  "\n?? at [abc]\nstack [0]:\n")
+  "\n?? at [abc]\nstack [0]:\n\n")
 
-(test-stdout "?? end of text"
+(test-stderr "?? end of text"
   '(* "abc" (??))
   "abc"
   @[]
-  "\n?? at []\nstack [0]:\n")
+  "\n?? at []\nstack [0]:\n\n")
 
-(test-stdout "?? between rules"
+(test-stderr "?? between rules"
   '(* "a" (??) "bc")
   "abc"
   @[]
-  "\n?? at [bc]\nstack [0]:\n")
+  "\n?? at [bc]\nstack [0]:\n\n")
 
-(test-stdout
+(test-stderr
   "?? stack display, string"
   '(* (<- "a") (??) "bc")
   "abc"
   @["a"]
-  (string/format "\n?? at [bc]\nstack [1]:\n  [0]: %M\n" "a"))
+  (string/format "\n?? at [bc]\nstack [1]:\n  [0]: %M\n\n" "a"))
 
-(test-stdout
+(test-stderr
   "?? stack display, multiple types"
   '(* (<- "a") (number :d) (constant true) (constant {}) (constant @[]) (??) "bc")
   "a1bc"
   @["a" 1 true {} @[]]
-  (string/format "\n?? at [bc]\nstack [5]:\n  [0]: %M\n  [1]: %M\n  [2]: %M\n  [3]: %M\n  [4]: %M\n" "a" 1 true {} @[]))
+  (string/format "\n?? at [bc]\nstack [5]:\n  [0]: %M\n  [1]: %M\n  [2]: %M\n  [3]: %M\n  [4]: %M\n\n" "a" 1 true {} @[]))
 
 (marshpeg '(* (??) "abc"))