From 7bfa864c65a2b6d2ad41f1edc8d18d57ffb3f968 Mon Sep 17 00:00:00 2001
From: Karen Arutyunov <karen@codesynthesis.com>
Date: Wed, 7 Oct 2020 17:24:11 +0300
Subject: Add support for BDEP_DEF_OPT environment variable

---
 bdep/bdep.cli |  6 ++++++
 bdep/bdep.cxx | 24 +++++++++++++++++++++---
 2 files changed, 27 insertions(+), 3 deletions(-)

diff --git a/bdep/bdep.cli b/bdep/bdep.cli
index 7c77958..45163e4 100644
--- a/bdep/bdep.cli
+++ b/bdep/bdep.cli
@@ -514,5 +514,11 @@ namespace bdep
   "\h|EXIT STATUS|
 
   Non-zero exit status is returned in case of an error.
+
+  \h|ENVIRONMENT|
+
+  The \cb{BDEP_DEF_OPT} environment variable is used to suppress loading of
+  default options files in nested \cb{bdep} invocations. Its values are
+  \cb{false} or \cb{0} to suppress and \cb{true} or \cb{1} to load.
   "
 }
diff --git a/bdep/bdep.cxx b/bdep/bdep.cxx
index 17d5f7d..14a36ba 100644
--- a/bdep/bdep.cxx
+++ b/bdep/bdep.cxx
@@ -152,6 +152,9 @@ init (const common_options& co,
       bool keep_sep,
       bool tmp)
 {
+  using bdep::optional;
+  using bdep::getenv;
+
   tracer trace ("init");
 
   O o;
@@ -211,14 +214,23 @@ init (const common_options& co,
            : o.V () ? 3 : o.v () ? 2 : o.quiet () ? 0 : 1;
   };
 
-  // Handle default options files.
+  // Load the default options files, unless --no-default-options is specified
+  // on the command line or the BDEP_DEF_OPT environment variable is set to a
+  // value other than 'true' or '1'.
+  //
+  optional<string> env_def (getenv ("BDEP_DEF_OPT"));
+
+  // False if --no-default-options is specified on the command line. Note that
+  // we cache the flag since it can be overridden by a default options file.
   //
+  bool cmd_def (!o.no_default_options ());
+
   // Note: don't need to use group_scaner (no arguments in options files).
   //
-  if (!o.no_default_options ()) // Command line option.
+  if (cmd_def && (!env_def || *env_def == "true" || *env_def == "1"))
   try
   {
-    bdep::optional<dir_path> extra;
+    optional<dir_path> extra;
     if (o.default_options_specified ())
       extra = o.default_options ();
 
@@ -246,6 +258,12 @@ init (const common_options& co,
          << e.second;
   }
 
+  // Propagate disabling of the default options files to the potential nested
+  // invocations.
+  //
+  if (!cmd_def && (!env_def || *env_def != "0"))
+    setenv ("BDEP_DEF_OPT", "0");
+
   // Global initializations.
   //
 
-- 
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