JS list decoding

3 files changed, 116 insertions, 97 deletions

diff --git a/src/gleam/dynamic.gleam b/src/gleam/dynamic.gleam
index d82ae79..5dd0feb 100644
--- a/src/gleam/dynamic.gleam
+++ b/src/gleam/dynamic.gleam
@@ -215,24 +215,35 @@ if javascript {
     "../gleam_stdlib.js" "decode_bool"
 }
 
+/// Checks to see whether a Dynamic value is a list, and return the list if it
+/// is.
+///
+/// If you wish to decode all the elements in the list use the `typed_list`
+/// instead.
+///
+/// ## Examples
+///
+///    > list(from(["a", "b", "c"]))
+///    Ok([from("a"), from("b"), from("c")])
+///
+///    > list(1)
+///    Error(DecodeError(expected: "Int", found: "Int"))
+///
+pub fn list(from value: Dynamic) -> Result(List(Dynamic), DecodeError) {
+  decode_list(value)
+}
+
 if erlang {
-  /// Checks to see whether a Dynamic value is a list, and return the list if it
-  /// is.
-  ///
-  /// If you wish to decode all the elements in the list use the `typed_list`
-  /// instead.
-  ///
-  /// ## Examples
-  ///
-  ///    > list(from(["a", "b", "c"]))
-  ///    Ok([from("a"), from("b"), from("c")])
-  ///
-  ///    > list(1)
-  ///    Error(DecodeError(expected: "Int", found: "Int"))
-  ///
-  pub external fn list(from: Dynamic) -> Result(List(Dynamic), DecodeError) =
+  external fn decode_list(Dynamic) -> Result(List(Dynamic), DecodeError) =
     "gleam_stdlib" "decode_list"
+}
 
+if javascript {
+  external fn decode_list(Dynamic) -> Result(List(Dynamic), DecodeError) =
+    "../gleam_stdlib.js" "decode_list"
+}
+
+if erlang {
   /// Checks to see whether a Dynamic value is a result, and return the result if
   /// it is.
   ///
@@ -287,37 +298,39 @@ if erlang {
         |> result.map(Error)
     }
   }
+}
 
-  /// Checks to see whether a Dynamic value is a list of a particular type, and
-  /// return the list if it is.
-  ///
-  /// The second argument is a decoder function used to decode the elements of
-  /// the list. The list is only decoded if all elements in the list can be
-  /// successfully decoded using this function.
-  ///
-  /// If you do not wish to decode all the elements in the list use the `list`
-  /// function instead.
-  ///
-  /// ## Examples
-  ///
-  ///    > typed_list(from(["a", "b", "c"]), of: string)
-  ///    Ok(["a", "b", "c"])
-  ///
-  ///    > typed_list(from([1, 2, 3]), of: string)
-  ///    Error(DecodeError(expected: "String", found: "Int"))
-  ///
-  ///    > typed_list(from("ok"), of: string)
-  ///    Error(DecodeError(expected: "List", found: "String"))
-  ///
-  pub fn typed_list(
-    from dynamic: Dynamic,
-    of decoder_type: fn(Dynamic) -> Result(inner, DecodeError),
-  ) -> Result(List(inner), DecodeError) {
-    dynamic
-    |> list
-    |> result.then(list.try_map(_, decoder_type))
-  }
+/// Checks to see whether a Dynamic value is a list of a particular type, and
+/// return the list if it is.
+///
+/// The second argument is a decoder function used to decode the elements of
+/// the list. The list is only decoded if all elements in the list can be
+/// successfully decoded using this function.
+///
+/// If you do not wish to decode all the elements in the list use the `list`
+/// function instead.
+///
+/// ## Examples
+///
+///    > typed_list(from(["a", "b", "c"]), of: string)
+///    Ok(["a", "b", "c"])
+///
+///    > typed_list(from([1, 2, 3]), of: string)
+///    Error(DecodeError(expected: "String", found: "Int"))
+///
+///    > typed_list(from("ok"), of: string)
+///    Error(DecodeError(expected: "List", found: "String"))
+///
+pub fn typed_list(
+  from dynamic: Dynamic,
+  of decoder_type: fn(Dynamic) -> Result(inner, DecodeError),
+) -> Result(List(inner), DecodeError) {
+  dynamic
+  |> list
+  |> result.then(list.try_map(_, decoder_type))
+}
 
+if erlang {
   /// Checks to see if a Dynamic value is a nullable version of a particular
   /// type, and return the Option if it is.
   ///
diff --git a/src/gleam_stdlib.js b/src/gleam_stdlib.js
index 47801ce..500066d 100644
--- a/src/gleam_stdlib.js
+++ b/src/gleam_stdlib.js
@@ -527,3 +527,7 @@ export function tuple_get(data, index) {
     ? new Ok(data[index])
     : new Error(Nil);
 }
+
+export function decode_list(data) {
+  return List.isList(data) ? new Ok(data) : decoder_error("List", data);
+}
diff --git a/test/gleam/dynamic_test.gleam b/test/gleam/dynamic_test.gleam
index fd28f79..c93210b 100644
--- a/test/gleam/dynamic_test.gleam
+++ b/test/gleam/dynamic_test.gleam
@@ -160,49 +160,49 @@ pub fn bool_test() {
   |> should.equal(Error(DecodeError(expected: "Bool", found: "List")))
 }
 
-if erlang {
-  pub fn typed_list_test() {
-    []
-    |> dynamic.from
-    |> dynamic.typed_list(dynamic.string)
-    |> should.equal(Ok([]))
+pub fn typed_list_test() {
+  []
+  |> dynamic.from
+  |> dynamic.typed_list(dynamic.string)
+  |> should.equal(Ok([]))
 
-    []
-    |> dynamic.from
-    |> dynamic.typed_list(dynamic.int)
-    |> should.equal(Ok([]))
+  []
+  |> dynamic.from
+  |> dynamic.typed_list(dynamic.int)
+  |> should.equal(Ok([]))
 
-    [1, 2, 3]
-    |> dynamic.from
-    |> dynamic.typed_list(dynamic.int)
-    |> should.equal(Ok([1, 2, 3]))
+  [1, 2, 3]
+  |> dynamic.from
+  |> dynamic.typed_list(dynamic.int)
+  |> should.equal(Ok([1, 2, 3]))
 
-    [[1], [2], [3]]
-    |> dynamic.from
-    |> dynamic.typed_list(dynamic.typed_list(_, dynamic.int))
-    |> should.equal(Ok([[1], [2], [3]]))
+  [[1], [2], [3]]
+  |> dynamic.from
+  |> dynamic.typed_list(dynamic.typed_list(_, dynamic.int))
+  |> should.equal(Ok([[1], [2], [3]]))
 
-    1
-    |> dynamic.from
-    |> dynamic.typed_list(dynamic.string)
-    |> should.be_error
+  1
+  |> dynamic.from
+  |> dynamic.typed_list(dynamic.string)
+  |> should.be_error
 
-    1.0
-    |> dynamic.from
-    |> dynamic.typed_list(dynamic.int)
-    |> should.be_error
+  1.0
+  |> dynamic.from
+  |> dynamic.typed_list(dynamic.int)
+  |> should.be_error
 
-    [""]
-    |> dynamic.from
-    |> dynamic.typed_list(dynamic.int)
-    |> should.be_error
+  [""]
+  |> dynamic.from
+  |> dynamic.typed_list(dynamic.int)
+  |> should.be_error
 
-    [dynamic.from(1), dynamic.from("not an int")]
-    |> dynamic.from
-    |> dynamic.typed_list(dynamic.int)
-    |> should.be_error
-  }
+  [dynamic.from(1), dynamic.from("not an int")]
+  |> dynamic.from
+  |> dynamic.typed_list(dynamic.int)
+  |> should.be_error
+}
 
+if erlang {
   pub fn optional_test() {
     1
     |> dynamic.from
@@ -730,29 +730,31 @@ if erlang {
     |> dynamic.map
     |> should.equal(Error(DecodeError(expected: "Map", found: "Int")))
   }
+}
 
-  pub fn list_test() {
-    []
-    |> dynamic.from
-    |> dynamic.list
-    |> should.equal(Ok([]))
+pub fn list_test() {
+  []
+  |> dynamic.from
+  |> dynamic.list
+  |> should.equal(Ok([]))
 
-    [1, 2]
-    |> dynamic.from
-    |> dynamic.list
-    |> should.equal(Ok([dynamic.from(1), dynamic.from(2)]))
+  [1, 2]
+  |> dynamic.from
+  |> dynamic.list
+  |> should.equal(Ok([dynamic.from(1), dynamic.from(2)]))
 
-    [dynamic.from(1), dynamic.from(2.0)]
-    |> dynamic.from
-    |> dynamic.list
-    |> should.equal(Ok([dynamic.from(1), dynamic.from(2.0)]))
+  [dynamic.from(1), dynamic.from(2.0)]
+  |> dynamic.from
+  |> dynamic.list
+  |> should.equal(Ok([dynamic.from(1), dynamic.from(2.0)]))
 
-    1
-    |> dynamic.from
-    |> dynamic.list
-    |> should.equal(Error(DecodeError(expected: "List", found: "Int")))
-  }
+  1
+  |> dynamic.from
+  |> dynamic.list
+  |> should.equal(Error(DecodeError(expected: "List", found: "Int")))
+}
 
+if erlang {
   pub fn result_test() {
     Ok(1)
     |> dynamic.from