Merge pull request #16 from zostay/deferred-error

feat: adding deferred.Error()

Author: zostay

.github/workflows/prepare.yaml

@@ -12,7 +12,7 @@ jobs:
       - uses: actions/checkout@v4
       - uses: actions/setup-go@v5
         with:
-          go-version: 1.19
+          go-version: 1.20
       - name: Release Verseion
         run: echo $RELEASE_VERSION=$(echo $GITHUB_REF_NAME | grep -Eo '[0-9]+\.[0-9]+\.[0-9]+.*$') >> $GITHUB_ENV
       - name: Version Check

.github/workflows/release.yaml

@@ -15,7 +15,7 @@ jobs:
       - uses: actions/checkout@v4
       - uses: actions/setup-go@v5
         with:
-          go-version: 1.19
+          go-version: 1.20
       - name: Release Verseion
         run: echo $RELEASE_VERSION=$(echo $GITHUB_REF_NAME | grep -Eo '[0-9]+\.[0-9]+\.[0-9]+.*$') >> $GITHUB_ENV
       - name: Version Check

.github/workflows/test.yaml

@@ -10,7 +10,7 @@ jobs:
       - uses: actions/checkout@v4
       - uses: actions/setup-go@v5
         with:
-          go-version: 1.19
+          go-version: '1.20'
           cache: false
       - uses: golangci/golangci-lint-action@v6
         with:

Changes.md

@@ -1,3 +1,8 @@
+## WIP  TBD
+
+ * :boom: Breaking Change :boom:: Now requires Go 1.20.
+ * Adding deferred.Error for helping with deferred error handling.
+
 ## v0.6.0  2023-08-12
 
  * Adding slices.Insert

README.md

@@ -4,6 +4,13 @@ There are a lot of common operations simply missing from the Golang builtin
 library. This makes up for that deficiency. Here's a summary of some of the
 provided tools:
 
+## Deferred Handling
+
+Handling deferred functions is a bit of a pain. This provides a way to handle
+certain deferred calls with a little less hassle:
+
+* `Error` (allows capturing both errors that may occur during defer)
+
 ## FileSystem Operations
 
 The built-in `io/fs` package is fine for reading files, but is missing write interfaces. This provides them:

deferred/error.go

@@ -0,0 +1,33 @@
+package deferred
+
+import "errors"
+
+// Error is intended to be used in cases where you have a deferred function that
+// returns an error and you want to capture that error, but you may have an error
+// that has already occurred and need to capture that too:
+//
+//		func ProcessFile(name string) (err error) {
+//			var r io.Reader
+//	     r, err = os.Open(name)
+//			if err != nil {
+//				return
+//			}
+//			defer deferred.Error(&err, r.Close())
+//
+//			// process file
+//			return
+//		}
+//
+// Now, both errors can be captured without a lot of gymnastics.
+func Error(err *error, deferErr error) {
+	if deferErr == nil {
+		return
+	}
+
+	if *err == nil {
+		*err = deferErr
+		return
+	}
+
+	*err = errors.Join(*err, deferErr)
+}

deferred/error_test.go

@@ -0,0 +1,52 @@
+package deferred_test
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+
+	"github.com/zostay/go-std/deferred"
+)
+
+func TestError(t *testing.T) {
+	t.Parallel()
+
+	errors := []error{
+		fmt.Errorf("error 1"),
+		fmt.Errorf("error 2"),
+	}
+
+	cases := []struct {
+		first, second error
+		name          string
+	}{
+		{nil, nil, "nil-nil"},
+		{errors[0], nil, "error-nil"},
+		{nil, errors[0], "nil-error"},
+		{errors[0], errors[1], "error-error"},
+	}
+
+	for _, c := range cases {
+		c := c
+		t.Run(c.name, func(t *testing.T) {
+			t.Parallel()
+
+			err := c.first
+			deferred.Error(&err, c.second)
+
+			if c.first == nil && c.second == nil {
+				assert.NoError(t, err, c.name)
+				return
+			}
+
+			assert.Error(t, err)
+			if c.first != nil {
+				assert.ErrorIs(t, err, c.first)
+			}
+			if c.second != nil {
+				assert.ErrorIs(t, err, c.second)
+			}
+		})
+	}
+}

go.mod

@@ -1,6 +1,6 @@
 module github.com/zostay/go-std
 
-go 1.19
+go 1.20
 
 require (
 	github.com/stretchr/testify v1.8.2