From 01c220360c539924dc9eadadba15b7f639bbde6e Mon Sep 17 00:00:00 2001
From: Michael Neumann <mneumann@ntecs.de>
Date: Sun, 9 Mar 2025 09:49:23 +0100
Subject: [PATCH 1/3] Remove surplus newlines (fixes #59)

Do a `flat_map_reduce` over the list of children and filter out any
child that is either `[]` or `nil`. The `count` is required to properly
detect the first non-blank item, which shouldn't be prefixed with a
new-line.

As the code is used in both `format` and `format_content`, factor it out
into `format_children`.

Fixes: #59
---
 lib/xml_builder.ex        | 26 +++++++++++++++++++++++---
 test/xml_builder_test.exs |  6 ++++++
 2 files changed, 29 insertions(+), 3 deletions(-)

diff --git a/lib/xml_builder.ex b/lib/xml_builder.ex
index d6872eb..77365a9 100644
--- a/lib/xml_builder.ex
+++ b/lib/xml_builder.ex
@@ -257,8 +257,7 @@ defmodule XmlBuilder do
     do: format({nil, nil, string}, level, options)
 
   defp format(list, level, options) when is_list(list) do
-    formatter = formatter(options)
-    map_intersperse(list, formatter.line_break(), &format(&1, level, options))
+    format_children(list, level, options)
   end
 
   defp format({nil, nil, name}, level, options) when is_bitstring(name),
@@ -339,6 +338,27 @@ defmodule XmlBuilder do
     ]
   end
 
+  defp format_children(list, level, options) when is_list(list) do
+    format_char = formatter(options).line_break()
+
+    {result, _} =
+      Enum.flat_map_reduce(list, 0, fn
+        [], count ->
+          {[], count}
+
+        nil, count ->
+          {[], count}
+
+        elm, 0 ->
+          {[format(elm, level, options)], 1}
+
+        elm, count ->
+          {[format_char, format(elm, level, options)], count + 1}
+      end)
+
+    result
+  end
+
   defp elements_with_prolog([first | rest]) when length(rest) > 0,
     do: [first_element(first) | element(rest)]
 
@@ -360,7 +380,7 @@ defmodule XmlBuilder do
 
   defp format_content(children, level, options) when is_list(children) do
     format_char = formatter(options).line_break()
-    [format_char, map_intersperse(children, format_char, &format(&1, level, options))]
+    [format_char, format_children(children, level, options)]
   end
 
   defp format_content(content, _level, _options),
diff --git a/test/xml_builder_test.exs b/test/xml_builder_test.exs
index 955b2a6..3cb7084 100644
--- a/test/xml_builder_test.exs
+++ b/test/xml_builder_test.exs
@@ -320,6 +320,12 @@ defmodule XmlBuilderTest do
     assert warning =~ "doc/1 is deprecated. Use document/1 with generate/1 instead."
   end
 
+  test "removal of empty child elements" do
+    assert {:person, nil, [nil, {:first, nil, "Josh"}, [], {:last, nil, "Nussbaum"}]}
+           |> XmlBuilder.generate() ==
+             ~s|<person>\n  <first>Josh</first>\n  <last>Nussbaum</last>\n</person>|
+  end
+
   def element(name, arg),
     do: XmlBuilder.element(name, arg) |> XmlBuilder.generate()
 

From 9b5ee43c2d93b38aafcfc1bc75d6d27da3293244 Mon Sep 17 00:00:00 2001
From: Michael Neumann <mneumann@ntecs.de>
Date: Sun, 9 Mar 2025 09:57:40 +0100
Subject: [PATCH 2/3] Slightly optimize "intersperse"

---
 lib/xml_builder.ex | 14 ++++++--------
 1 file changed, 6 insertions(+), 8 deletions(-)

diff --git a/lib/xml_builder.ex b/lib/xml_builder.ex
index 77365a9..4afe2d9 100644
--- a/lib/xml_builder.ex
+++ b/lib/xml_builder.ex
@@ -343,17 +343,15 @@ defmodule XmlBuilder do
 
     {result, _} =
       Enum.flat_map_reduce(list, 0, fn
-        [], count ->
+        elm, count when is_blank_list(elm) ->
           {[], count}
 
-        nil, count ->
-          {[], count}
-
-        elm, 0 ->
-          {[format(elm, level, options)], 1}
-
         elm, count ->
-          {[format_char, format(elm, level, options)], count + 1}
+          if format_char == "" or count == 0 do
+            {[format(elm, level, options)], count + 1}
+          else
+            {[format_char, format(elm, level, options)], count + 1}
+          end
       end)
 
     result

From d8f785ccf0b31490258350c432f73d6a2706e2fa Mon Sep 17 00:00:00 2001
From: Michael Neumann <mneumann@ntecs.de>
Date: Wed, 26 Mar 2025 23:41:16 +0100
Subject: [PATCH 3/3] Fix readability issues

---
 lib/xml_builder.ex | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/lib/xml_builder.ex b/lib/xml_builder.ex
index 4afe2d9..49e413c 100644
--- a/lib/xml_builder.ex
+++ b/lib/xml_builder.ex
@@ -339,18 +339,18 @@ defmodule XmlBuilder do
   end
 
   defp format_children(list, level, options) when is_list(list) do
-    format_char = formatter(options).line_break()
+    line_break = formatter(options).line_break()
 
     {result, _} =
       Enum.flat_map_reduce(list, 0, fn
-        elm, count when is_blank_list(elm) ->
+        element, count when is_blank_list(element) ->
           {[], count}
 
-        elm, count ->
-          if format_char == "" or count == 0 do
-            {[format(elm, level, options)], count + 1}
+        element, count ->
+          if line_break == "" or count == 0 do
+            {[format(element, level, options)], count + 1}
           else
-            {[format_char, format(elm, level, options)], count + 1}
+            {[line_break, format(element, level, options)], count + 1}
           end
       end)