From a4ff9f378ae7008e268d1c2facd44d049be6e930 Mon Sep 17 00:00:00 2001
From: Siri Hansen <siri@erlang.org>
Date: Wed, 12 Sep 2018 14:37:02 +0200
Subject: [logger] Include single_line option to report_cb

If the report callback function has two arguments, the second argument
is a map with options to limit the size of the log event. To even
allow a better formatting when the event shall be printed on a single
line, the new option single_line is now included in this
argument.
---
 lib/kernel/doc/src/logger_chapter.xml | 11 +++++++----
 lib/kernel/src/logger.erl             |  3 ++-
 lib/kernel/src/logger_formatter.erl   |  2 +-
 3 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/lib/kernel/doc/src/logger_chapter.xml b/lib/kernel/doc/src/logger_chapter.xml
index 26066d0777..4a81cfa34a 100644
--- a/lib/kernel/doc/src/logger_chapter.xml
+++ b/lib/kernel/doc/src/logger_chapter.xml
@@ -209,10 +209,13 @@
       <pre>fun((<seealso marker="logger#type-report"><c>logger:report()</c></seealso>,<seealso marker="logger#type-report_cb_config"><c>logger:report_cb_config()</c></seealso>) -> <seealso marker="stdlib:unicode#type-chardata"><c>unicode:chardata()</c></seealso>)
       </pre>
       <p>The fun must obey the <c>depth</c> and <c>chars_limit</c>
-	parameters provided in the second argument, as the formatter
-	can not do anything useful of these parameters with the
-	returned string. This variant is used when the formatting of
-	the report depends on the size parameters.</p>
+      parameters provided in the second argument, as the formatter can
+      not do anything useful of these parameters with the returned
+      string. The extra data also contains a field named
+      <c>single_line</c>, indicating if the printed log message may
+      contain line breaks or not. This variant is used when the
+      formatting of the report depends on the size or single line
+      parameters.</p>
       <p>Example, format string and arguments:</p>
       <code>logger:error("The file does not exist: ~ts",[Filename])</code>
       <p>Example, string:</p>
diff --git a/lib/kernel/src/logger.erl b/lib/kernel/src/logger.erl
index 0ada8b4924..752dd8d493 100644
--- a/lib/kernel/src/logger.erl
+++ b/lib/kernel/src/logger.erl
@@ -78,7 +78,8 @@
 -type report_cb() :: fun((report()) -> {io:format(),[term()]}) |
                      fun((report(),report_cb_config()) -> unicode:chardata()).
 -type report_cb_config() :: #{depth       := pos_integer() | unlimited,
-                              chars_limit := pos_integer() | unlimited}.
+                              chars_limit := pos_integer() | unlimited,
+                              single_line := boolean()}.
 -type msg_fun() :: fun((term()) -> {io:format(),[term()]} |
                                    report() |
                                    unicode:chardata()).
diff --git a/lib/kernel/src/logger_formatter.erl b/lib/kernel/src/logger_formatter.erl
index 59aa6ec3af..ded89bac9f 100644
--- a/lib/kernel/src/logger_formatter.erl
+++ b/lib/kernel/src/logger_formatter.erl
@@ -165,7 +165,7 @@ format_msg({report,Report},#{report_cb:=Fun}=Meta,Config) when is_function(Fun,1
                        Meta,Config)
     end;
 format_msg({report,Report},#{report_cb:=Fun}=Meta,Config) when is_function(Fun,2) ->
-    try Fun(Report,maps:with([depth,chars_limit],Config)) of
+    try Fun(Report,maps:with([depth,chars_limit,single_line],Config)) of
         Chardata when ?IS_STRING(Chardata) ->
             try chardata_to_list(Chardata) % already size limited by report_cb
             catch _:_ ->
-- 
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