feat: IteratorExt::collect_all

exn/src/iterator.rs

@@ -0,0 +1,67 @@
+// Copyright 2025 FastLabs Developers
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+/// Extension trait for [`Iterator`]s of [`Result`]s
+pub trait IteratorExt<T, E>: Iterator<Item = Result<T, E>> {
+    /// Transforms this [`Iterator`] of [`Result`]s into a [`Result`] of _collections_.
+    ///
+    /// This method produces a [`Result`] where _both_ the [`Ok`] and [`Err`] variants are
+    /// [`FromIterator`].
+    ///
+    /// Unlike [`Result`]'s [`FromIterator`] implementation, this method is _not_ short-circuiting;
+    /// it will always consume all items in `self`.
+    ///
+    /// This method pairs well with [`Exn::from_iter`][crate::Exn::from_iter]:
+    ///
+    /// ```
+    /// use std::io;
+    ///
+    /// use exn::Exn;
+    /// use exn::IteratorExt;
+    /// use exn::Result;
+    /// use exn::ResultExt;
+    ///
+    /// let files: Result<Vec<_>, io::Error> = ["a/b", "c/d", "e/f"]
+    ///     .into_iter()
+    ///     .map(|path| {
+    ///         std::fs::File::open(path)
+    ///             .or_raise(|| io::Error::other(format!("failed to open {path}")))
+    ///     })
+    ///     .collect_all::<_, Vec<_>>()
+    ///     .map_err(|children| Exn::from_iter(children, io::Error::other("failed to open all files")));
+    /// #
+    /// # drop(files);
+    /// ```
+    ///
+    /// # Errors
+    ///
+    /// Similar to [`Result`]'s [`FromIterator`] implementation, if any item is [`Err`], this
+    /// method will return [`Err`].
+    fn collect_all<A, B>(mut self) -> Result<A, B>
+    where
+        Self: Sized,
+        A: FromIterator<T>,
+        B: FromIterator<E>,
+    {
+        self.by_ref()
+            .collect::<Result<A, E>>()
+            .map_err(|first_err| {
+                std::iter::once(first_err)
+                    .chain(self.filter_map(Result::err))
+                    .collect()
+            })
+    }
+}
+
+impl<I, T, E> IteratorExt<T, E> for I where I: Iterator<Item = Result<T, E>> {}

exn/src/lib.rs

@@ -79,6 +79,7 @@ mod debug;
 mod display;
 mod ext;
 mod impls;
+mod iterator;
 mod macros;
 mod option;
 mod result;
@@ -87,6 +88,7 @@ pub use self::ext::ErrorExt;
 pub use self::ext::Ok;
 pub use self::impls::Exn;
 pub use self::impls::Frame;
+pub use self::iterator::IteratorExt;
 pub use self::option::OptionExt;
 pub use self::result::Result;
 pub use self::result::ResultExt;

exn/tests/simple.rs

@@ -14,6 +14,7 @@
 
 use exn::ErrorExt;
 use exn::Exn;
+use exn::IteratorExt;
 use exn::OptionExt;
 use exn::ResultExt;
 
@@ -116,3 +117,26 @@ fn test_ensure_fail() {
     let result = foo();
     insta::assert_debug_snapshot!(result.unwrap_err());
 }
+
+#[test]
+fn test_iterator_ext_ok() {
+    [Ok::<_, SimpleError>(()), Ok(()), Ok(())]
+        .into_iter()
+        .collect_all::<(), Vec<_>>()
+        .unwrap();
+}
+
+#[test]
+fn test_iterator_ext_err() {
+    let result = [
+        Ok(()),
+        Err(SimpleError("E1")),
+        Ok(()),
+        Err(SimpleError("E2")),
+    ]
+    .into_iter()
+    .collect_all::<(), Vec<_>>()
+    .map_err(|errs| Exn::from_iter(errs, SimpleError("An error")));
+
+    insta::assert_debug_snapshot!(result.unwrap_err());
+}

exn/tests/snapshots/simple__bail.snap

@@ -2,4 +2,4 @@
 source: exn/tests/simple.rs
 expression: result.unwrap_err()
 ---
-An error, at exn/tests/simple.rs:92:9
+An error, at exn/tests/simple.rs:93:9

exn/tests/snapshots/simple__ensure_fail.snap

@@ -2,4 +2,4 @@
 source: exn/tests/simple.rs
 expression: result.unwrap_err()
 ---
-An error, at exn/tests/simple.rs:112:9
+An error, at exn/tests/simple.rs:113:9

exn/tests/snapshots/simple__error_straightforward.snap

@@ -2,12 +2,12 @@
 source: exn/tests/simple.rs
 expression: e5
 ---
-E5, at exn/tests/simple.rs:37:17
+E5, at exn/tests/simple.rs:38:17
 |
-|-> E4, at exn/tests/simple.rs:36:17
+|-> E4, at exn/tests/simple.rs:37:17
 |
-|-> E3, at exn/tests/simple.rs:35:17
+|-> E3, at exn/tests/simple.rs:36:17
 |
-|-> E2, at exn/tests/simple.rs:34:17
+|-> E2, at exn/tests/simple.rs:35:17
 |
-|-> E1, at exn/tests/simple.rs:33:32
+|-> E1, at exn/tests/simple.rs:34:32

exn/tests/snapshots/simple__error_tree.snap

@@ -2,26 +2,26 @@
 source: exn/tests/simple.rs
 expression: e6
 ---
-E6, at exn/tests/simple.rs:60:14
+E6, at exn/tests/simple.rs:61:14
 |
-|-> E5, at exn/tests/simple.rs:52:14
+|-> E5, at exn/tests/simple.rs:53:14
 |   |
-|   |-> E3, at exn/tests/simple.rs:44:17
+|   |-> E3, at exn/tests/simple.rs:45:17
 |   |   |
-|   |   |-> E1, at exn/tests/simple.rs:43:32
+|   |   |-> E1, at exn/tests/simple.rs:44:32
 |   |
-|   |-> E10, at exn/tests/simple.rs:47:18
+|   |-> E10, at exn/tests/simple.rs:48:18
 |   |   |
-|   |   |-> E9, at exn/tests/simple.rs:46:32
+|   |   |-> E9, at exn/tests/simple.rs:47:32
 |   |
-|   |-> E12, at exn/tests/simple.rs:50:19
+|   |-> E12, at exn/tests/simple.rs:51:19
 |       |
-|       |-> E11, at exn/tests/simple.rs:49:34
+|       |-> E11, at exn/tests/simple.rs:50:34
 |
-|-> E4, at exn/tests/simple.rs:55:17
+|-> E4, at exn/tests/simple.rs:56:17
 |   |
-|   |-> E2, at exn/tests/simple.rs:54:32
+|   |-> E2, at exn/tests/simple.rs:55:32
 |
-|-> E8, at exn/tests/simple.rs:58:17
+|-> E8, at exn/tests/simple.rs:59:17
     |
-    |-> E7, at exn/tests/simple.rs:57:32
+    |-> E7, at exn/tests/simple.rs:58:32

exn/tests/snapshots/simple__from_error.snap

@@ -2,4 +2,4 @@
 source: exn/tests/simple.rs
 expression: result.unwrap_err()
 ---
-An error, at exn/tests/simple.rs:81:9
+An error, at exn/tests/simple.rs:82:9

exn/tests/snapshots/simple__iterator_ext_err.snap

@@ -0,0 +1,9 @@
+---
+source: exn/tests/simple.rs
+expression: result.unwrap_err()
+---
+An error, at exn/tests/simple.rs:139:21
+|
+|-> E1, at exn/tests/simple.rs:139:21
+|
+|-> E2, at exn/tests/simple.rs:139:21

exn/tests/snapshots/simple__option_ext.snap

@@ -2,4 +2,4 @@
 source: exn/tests/simple.rs
 expression: result.unwrap_err()
 ---
-An error, at exn/tests/simple.rs:74:25
+An error, at exn/tests/simple.rs:75:25

exn/tests/snapshots/simple__result_ext.snap

@@ -2,6 +2,6 @@
 source: exn/tests/simple.rs
 expression: result.unwrap_err()
 ---
-Another error, at exn/tests/simple.rs:67:25
+Another error, at exn/tests/simple.rs:68:25
 |
-|-> An error, at exn/tests/simple.rs:67:25
+|-> An error, at exn/tests/simple.rs:68:25