fn: add Collect+CollertErr function for iterators
What the developer wrote
Authored by Olaoluwa Osuntokun
fn: add Collect+CollertErr function for iterators
In this commit, we introduce a new utility function `Collect` to the fn
package. This function drains all elements from an iterator and returns
them as a slice. This is particularly useful when transitioning from
iterator-based APIs to code that expects slices, allowing for gradual
migration to the new iterator patterns.
The fn module's go.mod is also updated to require Go 1.23, which is
necessary for the built-in iter.Seq type support.
The replace directive will be removed once the fn package changes are
merged and a new version is tagged.
What changed, and why it matters
This commit adds two small helper functions, Collect and CollectErr, to a utility package. They simply turn Go 1.23 iterators into ordinary slices. There is no user-facing behavior change, no bug fix, and no security-related change.
No security action required. Review the temporary replace directive for build/release hygiene before the next tagged fn/v2 release.
Security signals we found
No strong security signals were identified.
Evidence from the diff
The change introduces iter.Seq/iter.Seq2 helpers in fn/iter.go, bumps fn/go.mod to Go 1.23, and temporarily replaces the published fn/v2 module with the local ./fn copy in the root go.mod. The functions are pure utilities that append iterator values to a slice; CollectErr stops at the first error. No existing code paths are modified.
Changed components
fn/iter.gofn/go.modgo.modgo.sumInspect captured patch +33 / −3
diff --git a/fn/go.mod b/fn/go.mod
index 89dc280..abf0cdf 100644
--- a/fn/go.mod
+++ b/fn/go.mod
@@ -1,6 +1,6 @@
module github.com/lightningnetwork/lnd/fn/v2
-go 1.19
+go 1.23
require (
github.com/stretchr/testify v1.8.1
diff --git a/fn/iter.go b/fn/iter.go
new file mode 100644
index 0000000..e6636aa
--- /dev/null
+++ b/fn/iter.go
@@ -0,0 +1,29 @@
+package fn
+
+import "iter"
+
+// Collect drains all of the elements from the passed iterator, returning a
+// slice of the contents.
+func Collect[T any](seq iter.Seq[T]) []T {
+
+ var ret []T
+ for i := range seq {
+ ret = append(ret, i)
+ }
+
+ return ret
+}
+
+// CollectErr drains all of the elements from the passed iterator with error
+// handling, returning a slice of the contents and the first error encountered.
+func CollectErr[T any](seq iter.Seq2[T, error]) ([]T, error) {
+ var ret []T
+ for val, err := range seq {
+ if err != nil {
+ return ret, err
+ }
+ ret = append(ret, val)
+ }
+
+ return ret, nil
+}
diff --git a/go.mod b/go.mod
index d1064da..9898b4d 100644
--- a/go.mod
+++ b/go.mod
@@ -206,6 +206,9 @@ require (
// store have been included in a tagged sqldb version.
replace github.com/lightningnetwork/lnd/sqldb => ./sqldb
+// Replace fn package to use local version with iterator Collect function.
+replace github.com/lightningnetwork/lnd/fn/v2 => ./fn
+
// This replace is for https://github.com/advisories/GHSA-25xm-hr59-7c27
replace github.com/ulikunitz/xz => github.com/ulikunitz/xz v0.5.11
diff --git a/go.sum b/go.sum
index 189b81c..ae6f41d 100644
--- a/go.sum
+++ b/go.sum
@@ -374,8 +374,6 @@ github.com/lightningnetwork/lnd/cert v1.2.2 h1:71YK6hogeJtxSxw2teq3eGeuy4rHGKcFf
github.com/lightningnetwork/lnd/cert v1.2.2/go.mod h1:jQmFn/Ez4zhDgq2hnYSw8r35bqGVxViXhX6Cd7HXM6U=
github.com/lightningnetwork/lnd/clock v1.1.1 h1:OfR3/zcJd2RhH0RU+zX/77c0ZiOnIMsDIBjgjWdZgA0=
github.com/lightningnetwork/lnd/clock v1.1.1/go.mod h1:mGnAhPyjYZQJmebS7aevElXKTFDuO+uNFFfMXK1W8xQ=
-github.com/lightningnetwork/lnd/fn/v2 v2.0.8 h1:r2SLz7gZYQPVc3IZhU82M66guz3Zk2oY+Rlj9QN5S3g=
-github.com/lightningnetwork/lnd/fn/v2 v2.0.8/go.mod h1:TOzwrhjB/Azw1V7aa8t21ufcQmdsQOQMDtxVOQWNl8s=
github.com/lightningnetwork/lnd/healthcheck v1.2.6 h1:1sWhqr93GdkWy4+6U7JxBfcyZIE78MhIHTJZfPx7qqI=
github.com/lightningnetwork/lnd/healthcheck v1.2.6/go.mod h1:Mu02um4CWY/zdTOvFje7WJgJcHyX2zq/FG3MhOAiGaQ=
github.com/lightningnetwork/lnd/kvdb v1.4.16 h1:9BZgWdDfjmHRHLS97cz39bVuBAqMc4/p3HX1xtUdbDI=
Why this scored 15/100
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