4 files changed, 10 insertions, 8 deletions
diff --git a/src/libutil/logging.cc b/src/libutil/logging.cc
index e860b27d3d0b..799c6e1ae441 100644
--- a/src/libutil/logging.cc
+++ b/src/libutil/logging.cc
@@ -53,7 +53,7 @@ public:
             prefix = std::string("<") + c + ">";
         }
 
-        writeToStderr(prefix + filterANSIEscapes(fs.s) + "\n");
+        writeToStderr(prefix + filterANSIEscapes(fs.s, !tty) + "\n");
     }
 
     void startActivity(ActivityId act, Verbosity lvl, ActivityType type,
diff --git a/src/libutil/util.cc b/src/libutil/util.cc
index 2391e14a94bd..a60ba8508e31 100644
--- a/src/libutil/util.cc
+++ b/src/libutil/util.cc
@@ -1185,7 +1185,7 @@ void ignoreException()
 }
 
 
-std::string filterANSIEscapes(const std::string & s, unsigned int width)
+std::string filterANSIEscapes(const std::string & s, bool filterAll, unsigned int width)
 {
     std::string t, e;
     size_t w = 0;
@@ -1210,7 +1210,7 @@ std::string filterANSIEscapes(const std::string & s, unsigned int width)
                 if (i != s.end() && *i >= 0x40 && *i <= 0x5f) e += *i++;
             }
 
-            if (last == 'm')
+            if (!filterAll && last == 'm')
                 t += e;
         }
 
diff --git a/src/libutil/util.hh b/src/libutil/util.hh
index c5c537ee63d8..500ab7811b93 100644
--- a/src/libutil/util.hh
+++ b/src/libutil/util.hh
@@ -391,11 +391,13 @@ void ignoreException();
 #define ANSI_BLUE "\e[34;1m"
 
 
-/* Truncate a string to 'width' printable characters. Certain ANSI
-   escape sequences (such as colour setting) are copied but not
-   included in the character count. Other ANSI escape sequences are
-   filtered. Also, tabs are expanded to spaces. */
+/* Truncate a string to 'width' printable characters. If 'filterAll'
+   is true, all ANSI escape sequences are filtered out. Otherwise,
+   some escape sequences (such as colour setting) are copied but not
+   included in the character count. Also, tabs are expanded to
+   spaces. */
 std::string filterANSIEscapes(const std::string & s,
+    bool filterAll = false,
     unsigned int width = std::numeric_limits<unsigned int>::max());
 
 
diff --git a/src/nix/progress-bar.cc b/src/nix/progress-bar.cc
index e6553c06f4ae..40b905ba3243 100644
--- a/src/nix/progress-bar.cc
+++ b/src/nix/progress-bar.cc
@@ -308,7 +308,7 @@ public:
         auto width = getWindowSize().second;
         if (width <= 0) std::numeric_limits<decltype(width)>::max();
 
-        writeToStderr("\r" + filterANSIEscapes(line, width) + "\e[K");
+        writeToStderr("\r" + filterANSIEscapes(line, false, width) + "\e[K");
     }
 
     std::string getStatus(State & state)