From 0501dd42c542f9ff4940bde057e39d3256b1be4d Mon Sep 17 00:00:00 2001
From: Matt Thornton <matthew.thornton13@gmail.com>
Date: Wed, 24 Nov 2021 13:48:08 +0000
Subject: [PATCH] Add a decoder for lists. (#32)

---
 .../Bind.fs                                   | 20 ++++-
 .../BindTests.fs                              | 88 +++++++++++++++++++
 2 files changed, 106 insertions(+), 2 deletions(-)

diff --git a/src/Symbolica.Extensions.Configuration.FSharp/Bind.fs b/src/Symbolica.Extensions.Configuration.FSharp/Bind.fs
index d3bba2b..32709ca 100644
--- a/src/Symbolica.Extensions.Configuration.FSharp/Bind.fs
+++ b/src/Symbolica.Extensions.Configuration.FSharp/Bind.fs
@@ -154,8 +154,7 @@ module Bind =
 
     /// <summary>
     /// Binds an <see cref="IConfigurationSection" /> as an <see cref="IDictionary" /> by applying the
-    /// <paramref name="keyBinder" /> to the key and the <paramref name="valueBinder" /> to the value
-    /// of each child section.
+    /// <paramref name="keyBinder" /> to the key and the <paramref name="valueBinder" /> to each child section.
     /// </summary>
     /// <param name="keyBinder">
     /// The <see cref="Binder" /> to apply to the key of each child section in order to convert it to the key type.
@@ -185,6 +184,23 @@ module Bind =
         |> Binder.mapFailure (Errors.AllOf >> Error.Many)
         |> Binder.map (fun x -> Dictionary(x) :> IDictionary<'key, 'value>)
 
+    /// <summary>
+    /// Binds an <see cref="IConfigurationSection" /> as a <see cref="List" /> by applying the
+    /// the <paramref name="valueBinder" /> to each child section.
+    /// </summary>
+    /// <param name="valueBinder">
+    /// The <see cref="Binder" /> to apply to each child section in order to convert it to the key type.
+    /// Note this can be either a simple value binder or a binder for a more complex type that spans
+    /// multiple child sections.
+    /// </param>
+    let list (valueBinder: Binder<IConfigurationSection, 'value, Error>) : Binder<'config, 'value list, Error> =
+        dict Binder.ask valueBinder
+        |> Binder.map (
+            Seq.sortBy (fun x -> x.Key)
+            >> Seq.map (fun x -> x.Value)
+            >> List.ofSeq
+        )
+
     /// <summary>Creates a <see cref="Binder" /> from a System.Type.TryParse style parsing function.</summary>
     /// <remarks>
     /// Useful for creating a parser for a primitive type for which a <c>TryParse</c> function already exists.
diff --git a/tests/Symbolica.Extensions.Configuration.FSharp.Tests/BindTests.fs b/tests/Symbolica.Extensions.Configuration.FSharp.Tests/BindTests.fs
index 3c2f45e..016431b 100644
--- a/tests/Symbolica.Extensions.Configuration.FSharp.Tests/BindTests.fs
+++ b/tests/Symbolica.Extensions.Configuration.FSharp.Tests/BindTests.fs
@@ -678,6 +678,94 @@ module Dict =
                 )
             ) @>
 
+module List =
+
+    type CustomType = { Prop: int }
+
+    [<Property(Arbitrary = [| typeof<ConfigurationArb> |])>]
+    let ``should be success ordered by keys if all values can be decoded`` path =
+        let section =
+            { Children =
+                [ { Children = Seq.empty
+                    Path = "foo" |> ConfigPathSegment
+                    Value = "foo" }
+                  { Children = Seq.empty
+                    Path = "bar" |> ConfigPathSegment
+                    Value = "bar" }
+                  { Children = Seq.empty
+                    Path = "4" |> ConfigPathSegment
+                    Value = "4" }
+                  { Children = Seq.empty
+                    Path = "0" |> ConfigPathSegment
+                    Value = "0" }
+                  { Children = Seq.empty
+                    Path = "1" |> ConfigPathSegment
+                    Value = "1" } ]
+              Path = path
+              Value = null }
+
+        test
+            <@ Bind.list (Bind.value Bind.string)
+               |> Binder.eval section = Success["0"
+                                                "1"
+                                                "4"
+                                                "bar"
+                                                "foo"] @>
+
+    [<Property(Arbitrary = [| typeof<ConfigurationArb> |])>]
+    let ``should be success if key and complex value can be decoded`` path key value =
+        let bindCustomType =
+            bind {
+                let! prop = Bind.valueAt "prop" Bind.int
+                return { Prop = prop }
+            }
+
+        let section =
+            { Children =
+                [ { Children =
+                      [ { Children = Seq.empty
+                          Path = "prop" |> ConfigPathSegment
+                          Value = value |> string } ]
+                    Path = key
+                    Value = null } ]
+              Path = path
+              Value = null }
+
+        test <@ Bind.list bindCustomType |> Binder.eval section = Success[{ Prop = value }] @>
+
+    [<Property(Arbitrary = [| typeof<ConfigurationArb> |])>]
+    let ``should be failure if any value cannot be decoded`` path =
+        let section =
+            { Children =
+                [ { Children = Seq.empty
+                    Path = "1" |> ConfigPathSegment
+                    Value = "foo" }
+                  { Children = Seq.empty
+                    Path = "2" |> ConfigPathSegment
+                    Value = "bar" }
+                  { Children = Seq.empty
+                    Path = "3" |> ConfigPathSegment
+                    Value = "true" } ]
+              Path = path
+              Value = null }
+
+        test
+            <@ Bind.list (Bind.value Bind.bool)
+               |> Binder.eval section = Failure(
+                Error.Many(
+                    Errors.AllOf(
+                        Error.SectionError(
+                            "1",
+                            Error.Many(Errors.single (Error.ValueError("foo", ValueError.invalidType<bool>)))
+                        )
+                        +& Error.SectionError(
+                            "2",
+                            Error.Many(Errors.single (Error.ValueError("bar", ValueError.invalidType<bool>)))
+                        )
+                    )
+                )
+            ) @>
+
 module Bool =
     [<Property>]
     let ``should be Success value if can be converted to bool`` value =