Add --[no]diag-color options (infrastructure only)

5 files changed, 97 insertions, 23 deletions

diff --git a/bpkg/bpkg.cxx b/bpkg/bpkg.cxx
index 2a9fb6d..3ede99e 100644
--- a/bpkg/bpkg.cxx
+++ b/bpkg/bpkg.cxx
@@ -2,6 +2,8 @@
 // license   : MIT; see accompanying LICENSE file
 
 #include <limits>
+#include <cstdlib>     // getenv()
+#include <cstring>     // strcmp()
 #include <iostream>
 #include <exception>   // set_terminate(), terminate_handler
 #include <type_traits> // enable_if, is_base_of
@@ -161,12 +163,15 @@ namespace bpkg
 
       init_diag (bc.verbosity,
                  bo.silent (),
-                 (bc.progress       ? bc.progress :
-                  co.progress ()    ? optional<bool> (true) :
-                  co.no_progress () ? optional<bool> (false) : nullopt),
+                 (bc.progress         ? bc.progress :
+                  co.progress ()      ? optional<bool> (true)  :
+                  co.no_progress ()   ? optional<bool> (false) : nullopt),
+                 (bc.diag_color       ? bc.diag_color :
+                  co.diag_color ()    ? optional<bool> (true)  :
+                  co.no_diag_color () ? optional<bool> (false) : nullopt),
                  bo.no_line (),
                  bo.no_column (),
-                 bpkg::stderr_term);
+                 bpkg::stderr_term.has_value ());
 
       // Note that we pretend to be in the serial-stop mode even though we may
       // build build system modules in parallel in order to get better
@@ -465,31 +470,48 @@ init (const common_options& co,
 
     // Verify common options.
     //
-    // Also merge the --progress/--no-progress options, overriding a less
-    // specific flag with a more specific.
+    // Also merge the --*/--no-* options, overriding a less specific flag with
+    // a more specific.
     //
-    optional<bool> progress;
-    auto merge_progress = [&progress]
-                          (const O& o,
-                           const default_options_entry<O>* e = nullptr)
+    //
+    optional<bool> progress, diag_color;
+    auto merge_no = [&progress, &diag_color] (
+      const O& o,
+      const default_options_entry<O>* e = nullptr)
     {
-      if (o.progress () && o.no_progress ())
       {
-        diag_record dr;
-        (e != nullptr ? dr << fail (e->file) : dr << fail)
+        if (o.progress () && o.no_progress ())
+        {
+          diag_record dr;
+          (e != nullptr ? dr << fail (e->file) : dr << fail)
           << "both --progress and --no-progress specified";
+        }
+
+        if (o.progress ())
+          progress = true;
+        else if (o.no_progress ())
+          progress = false;
       }
 
-      if (o.progress ())
-        progress = true;
-      else if (o.no_progress ())
-        progress = false;
+      {
+        if (o.diag_color () && o.no_diag_color ())
+        {
+          diag_record dr;
+          (e != nullptr ? dr << fail (e->file) : dr << fail)
+          << "both --diag-color and --no-diag-color specified";
+        }
+
+        if (o.diag_color ())
+          diag_color = true;
+        else if (o.no_diag_color ())
+          diag_color = false;
+      }
     };
 
     for (const default_options_entry<O>& e: dos)
-      merge_progress (e.options, &e);
+      merge_no (e.options, &e);
 
-    merge_progress (o);
+    merge_no (o);
 
     o = merge_options (dos, o);
 
@@ -498,6 +520,12 @@ init (const common_options& co,
       o.progress (*progress);
       o.no_progress (!*progress);
     }
+
+    if (diag_color)
+    {
+      o.diag_color (*diag_color);
+      o.no_diag_color (!*diag_color);
+    }
   }
   catch (const invalid_argument& e)
   {
@@ -544,7 +572,24 @@ try
 
   default_terminate = set_terminate (custom_terminate);
 
-  stderr_term = fdterm (stderr_fd ());
+  if (fdterm (stderr_fd ()))
+  {
+    stderr_term = std::getenv ("TERM");
+
+    stderr_term_color =
+#ifdef _WIN32
+      // For now we disable color on Windows since it's unclear if/where/how
+      // it is supported. Maybe one day someone will figure this out.
+      //
+      false
+#else
+      // This test was lifted from GCC (Emacs shell sets TERM=dumb).
+      //
+      *stderr_term != nullptr && strcmp (*stderr_term, "dumb") != 0
+#endif
+      ;
+  }
+
   exec_dir = path (argv[0]).directory ();
   build2_argv0 = argv[0];
 
diff --git a/bpkg/common.cli b/bpkg/common.cli
index ac045d0..d870a8d 100644
--- a/bpkg/common.cli
+++ b/bpkg/common.cli
@@ -134,6 +134,18 @@ namespace bpkg
        network transfers, building, etc."
     }
 
+    bool --diag-color
+    {
+      "Use color in diagnostics. If printing to a terminal the color is used
+       by default provided the terminal is not dumb. Use \cb{--no-diag-color}
+       to suppress."
+    }
+
+    bool --no-diag-color
+    {
+      "Don't use color in diagnostics."
+    }
+
     path --build
     {
       "<path>",
diff --git a/bpkg/utility.cxx b/bpkg/utility.cxx
index 68d79ad..467e01f 100644
--- a/bpkg/utility.cxx
+++ b/bpkg/utility.cxx
@@ -161,7 +161,8 @@ namespace bpkg
     }
   }
 
-  bool stderr_term;
+  optional<const char*> stderr_term = nullopt;
+  bool stderr_term_color = false;
 
   bool
   yn_prompt (const string& p, char d)
diff --git a/bpkg/utility.hxx b/bpkg/utility.hxx
index 342d608..1f5c725 100644
--- a/bpkg/utility.hxx
+++ b/bpkg/utility.hxx
@@ -152,9 +152,17 @@ namespace bpkg
   dir_path
   current_directory ();
 
-  // Progress.
+  // Diagnostics.
   //
-  extern bool stderr_term; // True if stderr is a terminal.
+  // If stderr is not a terminal, then the value is absent (so can be used as
+  // bool). Otherwise, it is the value of the TERM environment variable (which
+  // can be NULL).
+  //
+  extern optional<const char*> stderr_term;
+
+  // True if the color can be used on the stderr terminal.
+  //
+  extern bool stderr_term_color;
 
   // Y/N prompt. See butl::yn_prompt() for details (this is a thin wrapper).
   //
diff --git a/bpkg/utility.txx b/bpkg/utility.txx
index 47619c6..6113e4e 100644
--- a/bpkg/utility.txx
+++ b/bpkg/utility.txx
@@ -74,6 +74,14 @@ namespace bpkg
       if (no_progress)
         ops.push_back ("--no-progress");
 
+      // Forward our --[no]diag-color options.
+      //
+      if (co.diag_color ())
+        ops.push_back ("--diag-color");
+
+      if (co.no_diag_color ())
+        ops.push_back ("--no-diag-color");
+
       return process_start_callback (
         [] (const char* const args[], size_t n)
         {