From 479b4c4862972b9f7e796927b71674fd88cdb407 Mon Sep 17 00:00:00 2001
From: NoneTheWisr <12655815+NoneTheWisr@users.noreply.github.com>
Date: Sun, 16 Jan 2022 12:47:28 +0400
Subject: [PATCH] Add Itertools::enumerate_ok

Squashed commit of the following:

commit 146fb0e30de632787daffcf3208f30878490225b
Author: NoneTheWisr <12655815+NoneTheWisr@users.noreply.github.com>
Date:   Sun Jan 16 12:44:41 2022 +0400

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commit aa2db90da74f3b7be72f0456f281c20785a38e2f
Author: NoneTheWisr <12655815+NoneTheWisr@users.noreply.github.com>
Date:   Sun Jan 16 12:19:55 2022 +0400

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commit f473fee490788b468f08ca911b0fb96e27b82129
Author: sshah1 <saatvik.shah@imc.com>
Date:   Sun Jan 16 09:09:32 2022 +0100

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commit ff4628c27ffdcdbc8ab324dc5b4702d650cc7a45
Author: Preet Dua <615318+prabhpreet@users.noreply.github.com>
Date:   Sat Jan 15 23:58:18 2022 -0800

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commit 90bdeb6c313ca22c59af26fbf61a22f41374b959
Author: NoneTheWisr <12655815+NoneTheWisr@users.noreply.github.com>
Date:   Sun Jan 16 11:46:53 2022 +0400

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commit 7044ed31f7f0303976214efa000e0a6b36daa341
Author: Shahar Dawn Or <mightyiampresence@gmail.com>
Date:   Sat Jan 15 16:58:27 2022 +0700

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commit 659639e64a21407f0f7556355abbc29e07bcfa9d
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Date:   Sat Jan 15 13:54:21 2022 +0400

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commit a305d9745428bb9d56d21d3e9f69dadc45ac6356
Author: Preet Dua <615318+prabhpreet@users.noreply.github.com>
Date:   Sat Jan 15 01:43:33 2022 -0800

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commit f08c2afa2b9a177056befa72b0ce1ab9032e62e8
Author: Roland Fredenhagen <dev@modprog.de>
Date:   Sat Jan 15 10:33:59 2022 +0100

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commit 48bd0321e205e8dfaa8d1bbbdd370a6583f07eeb
Author: Shahar Dawn Or <mightyiampresence@gmail.com>
Date:   Sat Jan 15 16:22:06 2022 +0700

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commit db02884e85df53995b767b80d6f658ed19c43062
Author: NoneTheWisr <12655815+NoneTheWisr@users.noreply.github.com>
Date:   Sat Jan 15 13:10:44 2022 +0400

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Co-authored-by: sshah1 <saatvik.shah@imc.com>
Co-authored-by: Roland Fredenhagen <dev@modprog.de>
Co-authored-by: Shahar Dawn Or <mightyiampresence@gmail.com>
Co-authored-by: Preet Dua <615318+prabhpreet@users.noreply.github.com>
---
 src/adaptors/mod.rs | 44 ++++++++++++++++++++++++++++++++++++++++++++
 src/lib.rs          | 18 ++++++++++++++++++
 2 files changed, 62 insertions(+)

diff --git a/src/adaptors/mod.rs b/src/adaptors/mod.rs
index 2010f535b..6a57ce566 100644
--- a/src/adaptors/mod.rs
+++ b/src/adaptors/mod.rs
@@ -839,6 +839,50 @@ impl_tuple_combination!(Tuple10Combination Tuple9Combination; a b c d e f g h i)
 impl_tuple_combination!(Tuple11Combination Tuple10Combination; a b c d e f g h i j);
 impl_tuple_combination!(Tuple12Combination Tuple11Combination; a b c d e f g h i j k);
 
+/// An iterator adapter to enumerate values within a nested `Result::Ok`.
+///
+/// See [`.enumerate_ok()`](crate::Itertools::enumerate_ok) for more information.
+#[derive(Clone)]
+#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
+pub struct EnumerateOk<I> {
+    iter: I,
+    index: usize
+}
+
+/// Create a new `EnumerateOk` iterator.
+pub fn enumerate_ok<I, T, E>(iter: I) -> EnumerateOk<I>
+where
+    I: Iterator<Item = Result<T, E>>,
+{
+    EnumerateOk {
+        iter,
+        index: 0
+    }
+}
+
+impl<I> fmt::Debug for EnumerateOk<I>
+where
+    I: fmt::Debug,
+{
+    debug_fmt_fields!(EnumerateOk, iter);
+}
+
+impl<I,T,E> Iterator for EnumerateOk<I>
+    where I: Iterator<Item = Result<T,E>>,
+{
+    type Item = Result<(usize,T),E>;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        self.iter.next().map(|item| {
+            item.map(|v| {
+                let index = self.index;
+                self.index +=1;
+                (index,v)
+            })
+        })
+    }
+}
+
 /// An iterator adapter to filter values within a nested `Result::Ok`.
 ///
 /// See [`.filter_ok()`](crate::Itertools::filter_ok) for more information.
diff --git a/src/lib.rs b/src/lib.rs
index df95e19ba..ce7ea77ab 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -99,6 +99,7 @@ pub mod structs {
         Batching,
         MapInto,
         MapOk,
+        EnumerateOk,
         Merge,
         MergeBy,
         TakeWhileRef,
@@ -846,6 +847,23 @@ pub trait Itertools : Iterator {
         self.map_ok(f)
     }
 
+    /// Return an iterator adaptor that adds an index to `Result::Ok`
+    /// values. `Result::Err` values are unchanged. The index is incremented
+    /// only for `Result::Ok` values.
+    ///
+    /// ```
+    /// use itertools::Itertools;
+    ///
+    /// let input = vec![Ok(41), Err(false), Ok(11)];
+    /// let it = input.into_iter().enumerate_ok();
+    /// itertools::assert_equal(it, vec![Ok((0, 41)), Err(false), Ok((1, 11))]);
+    /// ```
+    fn enumerate_ok<T, E>(self) -> EnumerateOk<Self>
+        where Self: Iterator<Item = Result<T, E>> + Sized,
+    {
+        adaptors::enumerate_ok(self)
+    }
+
     /// Return an iterator adaptor that applies the provided closure
     /// to every `Result::Ok` value. `Result::Err` values are
     /// unchanged.