From 869aff19338e474f003398aad0a251621df3517c Mon Sep 17 00:00:00 2001
From: Louis Pilfold <louis@lpil.uk>
Date: Tue, 30 Jun 2020 13:31:59 +0100
Subject: Fix crash with unmodified bit builder

---
 src/gleam/bit_builder.gleam              |  2 +-
 src/gleam_stdlib.erl                     |  5 ++-
 test/gleam/bit_builder_test.gleam        | 65 ++++++++++++++++++++++++++++++++
 test/gleam/bit_string_builder_test.gleam | 58 ----------------------------
 4 files changed, 70 insertions(+), 60 deletions(-)
 create mode 100644 test/gleam/bit_builder_test.gleam
 delete mode 100644 test/gleam/bit_string_builder_test.gleam

diff --git a/src/gleam/bit_builder.gleam b/src/gleam/bit_builder.gleam
index c3c88b0..dc066ae 100644
--- a/src/gleam/bit_builder.gleam
+++ b/src/gleam/bit_builder.gleam
@@ -74,7 +74,7 @@ pub external fn concat(List(BitBuilder)) -> BitBuilder =
 /// Runs in constant time.
 ///
 pub external fn from_bit_string(BitString) -> BitBuilder =
-  "gleam_stdlib" "identity"
+  "gleam_stdlib" "wrap_list"
 
 /// Turns an builder into a bit string.
 ///
diff --git a/src/gleam_stdlib.erl b/src/gleam_stdlib.erl
index f84e658..fa5f8fd 100644
--- a/src/gleam_stdlib.erl
+++ b/src/gleam_stdlib.erl
@@ -11,7 +11,7 @@
          string_pad/4, decode_tuple2/1, decode_map/1, bit_string_int_to_u32/1,
          bit_string_int_from_u32/1, bit_string_append/2, bit_string_part_/3,
          decode_bit_string/1, compile_regex/2, regex_match/2, regex_split/2,
-         regex_scan/2, base_decoded4/1]).
+         regex_scan/2, base_decoded4/1, wrap_list/1]).
 
 should_equal(Actual, Expected) -> ?assertEqual(Expected, Actual).
 should_not_equal(Actual, Expected) -> ?assertNotEqual(Expected, Actual).
@@ -205,3 +205,6 @@ base_decoded4(S) ->
   try {ok, base64:decode(S)}
   catch error:badarith -> {error, nil}
   end.
+
+wrap_list(X) when is_list(X) -> X;
+wrap_list(X) -> [X].
diff --git a/test/gleam/bit_builder_test.gleam b/test/gleam/bit_builder_test.gleam
new file mode 100644
index 0000000..b1635e5
--- /dev/null
+++ b/test/gleam/bit_builder_test.gleam
@@ -0,0 +1,65 @@
+import gleam/should
+import gleam/bit_builder
+
+pub fn builder_test() {
+  let data = bit_builder.from_bit_string(<<1>>)
+    |> bit_builder.append(<<2>>)
+    |> bit_builder.append(<<3>>)
+    |> bit_builder.prepend(<<0>>)
+
+  data
+  |> bit_builder.to_bit_string
+  |> should.equal(<<0, 1, 2, 3>>)
+
+  data
+  |> bit_builder.byte_size
+  |> should.equal(4)
+}
+
+pub fn builder_with_strings_test() {
+  let data = bit_builder.from_bit_string(<<1>>)
+    |> bit_builder.append_string("2")
+    |> bit_builder.append_string("3")
+    |> bit_builder.prepend_string("0")
+
+  data
+  |> bit_builder.to_bit_string
+  |> should.equal(<<"0":utf8, 1, "2":utf8, "3":utf8>>)
+
+  data
+  |> bit_builder.byte_size
+  |> should.equal(4)
+}
+
+pub fn builder_with_builders_test() {
+  let data = bit_builder.from_bit_string(<<1>>)
+    |> bit_builder.append_builder(bit_builder.from_bit_string(<<2>>))
+    |> bit_builder.append_builder(bit_builder.from_bit_string(<<3>>))
+    |> bit_builder.prepend_builder(bit_builder.from_bit_string(<<0>>))
+
+  data
+  |> bit_builder.to_bit_string
+  |> should.equal(<<0, 1, 2, 3>>)
+
+  data
+  |> bit_builder.byte_size
+  |> should.equal(4)
+}
+
+pub fn concat_test() {
+  [
+    bit_builder.from_bit_string(<<1, 2>>),
+    bit_builder.from_bit_string(<<3, 4>>),
+    bit_builder.from_bit_string(<<5, 6>>),
+  ]
+  |> bit_builder.concat
+  |> bit_builder.to_bit_string
+  |> should.equal(<<1, 2, 3, 4, 5, 6>>)
+}
+
+pub fn from_string_test() {
+  // Regression test: no additional modification of the builder
+  bit_builder.from_bit_string(<<>>)
+  |> bit_builder.to_bit_string
+  |> should.equal(<<>>)
+}
diff --git a/test/gleam/bit_string_builder_test.gleam b/test/gleam/bit_string_builder_test.gleam
deleted file mode 100644
index 43e010a..0000000
--- a/test/gleam/bit_string_builder_test.gleam
+++ /dev/null
@@ -1,58 +0,0 @@
-import gleam/should
-import gleam/bit_builder
-
-pub fn builder_test() {
-  let data = bit_builder.from_bit_string(<<1>>)
-    |> bit_builder.append(<<2>>)
-    |> bit_builder.append(<<3>>)
-    |> bit_builder.prepend(<<0>>)
-
-  data
-  |> bit_builder.to_bit_string
-  |> should.equal(<<0, 1, 2, 3>>)
-
-  data
-  |> bit_builder.byte_size
-  |> should.equal(4)
-}
-
-pub fn builder_with_strings_test() {
-  let data = bit_builder.from_bit_string(<<1>>)
-    |> bit_builder.append_string("2")
-    |> bit_builder.append_string("3")
-    |> bit_builder.prepend_string("0")
-
-  data
-  |> bit_builder.to_bit_string
-  |> should.equal(<<"0":utf8, 1, "2":utf8, "3":utf8>>)
-
-  data
-  |> bit_builder.byte_size
-  |> should.equal(4)
-}
-
-pub fn builder_with_builders_test() {
-  let data = bit_builder.from_bit_string(<<1>>)
-    |> bit_builder.append_builder(bit_builder.from_bit_string(<<2>>))
-    |> bit_builder.append_builder(bit_builder.from_bit_string(<<3>>))
-    |> bit_builder.prepend_builder(bit_builder.from_bit_string(<<0>>))
-
-  data
-  |> bit_builder.to_bit_string
-  |> should.equal(<<0, 1, 2, 3>>)
-
-  data
-  |> bit_builder.byte_size
-  |> should.equal(4)
-}
-
-pub fn concat_test() {
-  [
-    bit_builder.from_bit_string(<<1, 2>>),
-    bit_builder.from_bit_string(<<3, 4>>),
-    bit_builder.from_bit_string(<<5, 6>>),
-  ]
-  |> bit_builder.concat
-  |> bit_builder.to_bit_string
-  |> should.equal(<<1, 2, 3, 4, 5, 6>>)
-}
-- 
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