Import code from github.com/lestrrat-go/jwx

.github/workflows/ci.yml

@@ -0,0 +1,35 @@
+name: CI
+on: [push, pull_request]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        go: [ '1.15', '1.16' ]
+    name: Go ${{ matrix.go }} test
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v2
+      - name: Install Go stable version
+        if: matrix.go != 'tip'
+        uses: actions/setup-go@v2
+        with:
+          go-version: ${{ matrix.go }}
+      - name: Install Go tip
+        if: matrix.go == 'tip'
+        run: |
+          git clone --depth=1 https://go.googlesource.com/go $HOME/gotip
+          cd $HOME/gotip/src
+          ./make.bash
+          echo "::set-env name=GOROOT::$HOME/gotip"
+          echo "::add-path::$HOME/gotip/bin"
+          echo "::add-path::$(go env GOPATH)/bin"
+      - name: Test
+        run: go test -v -race ./...
+      - name: Upload code coverage to codecov
+        if: matrix.go == '1.16'
+        uses: codecov/codecov-action@v1
+        with:
+          file: ./coverage.out
+

.github/workflows/lint.yml

@@ -0,0 +1,11 @@
+name: lint
+on: [push, pull_request]
+jobs:
+  golangci:
+    name: lint
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - uses: golangci/golangci-lint-action@v2
+        with:
+          version: v1.39.0

README.md

@@ -1,2 +1,3 @@
 # blackmagic
-Reflect-based black magic 
+
+Reflect-based black magic. YMMV, and use with caution

blackmagic.go

@@ -0,0 +1,55 @@
+package blackmagic
+
+import (
+	"reflect"
+
+	"github.com/pkg/errors"
+)
+
+// AssignIfCompatible is a convenience function to safely
+// assign arbitrary values. dst must be a pointer to an
+// empty interface, or it must be a pointer to a compatible
+// variable type that can hold src.
+func AssignIfCompatible(dst, src interface{}) error {
+	orv := reflect.ValueOf(src) // save this value for error reporting
+	result := orv
+
+	// t can be a pointer or a slice, and the code will slightly change
+	// depending on this
+	var isSlice bool
+	switch result.Kind() {
+	case reflect.Ptr:
+		// no op
+	case reflect.Slice:
+		isSlice = true
+	default:
+		return errors.Errorf("argument t to AssignIfCompatible must be a pointer or a slice: %T", src)
+	}
+
+	rv := reflect.ValueOf(dst)
+	if rv.Kind() != reflect.Ptr {
+		return errors.Errorf(`argument to AssignIfCompatible() must be a pointer: %T`, dst)
+	}
+
+	actualDst := rv.Elem()
+	switch actualDst.Kind() {
+	case reflect.Interface:
+		// If it's an interface, we can just assign the pointer to the interface{}
+	default:
+		// If it's a pointer to the struct we're looking for, we need to set
+		// the de-referenced struct
+		if !isSlice {
+			result = result.Elem()
+		}
+	}
+	if !result.Type().AssignableTo(actualDst.Type()) {
+		return errors.Errorf(`argument to AssignIfCompatible() must be compatible with %T (was %T)`, orv.Interface(), dst)
+	}
+
+	if !actualDst.CanSet() {
+		return errors.Errorf(`argument to AssignIfCompatible() must be settable`)
+	}
+	actualDst.Set(result)
+
+	return nil
+}

blackmagic_test.go

@@ -0,0 +1,61 @@
+package blackmagic_test
+
+import (
+	"testing"
+
+	"github.com/lestrrat-go/blackmagic"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestAssignment(t *testing.T) {
+	testcases := []struct {
+		Name        string
+		Error       bool
+		Value       interface{}
+		Destination func() interface{}
+	}{
+		{
+			Name:  `empty struct`,
+			Error: true,
+			Value: struct{}{},
+			Destination: func() interface{} {
+				var v interface{}
+				return &v
+			},
+		},
+		{
+			Name:  `non pointer destination`,
+			Error: true,
+			Value: &struct{}{},
+		},
+		{
+			Name:  `assign empty struct to int`,
+			Error: true,
+			Value: &struct{}{},
+			Destination: func() interface{} {
+				var v int
+				return &v
+			},
+		},
+	}
+
+	for _, tc := range testcases {
+		tc := tc
+		t.Run(tc.Name, func(t *testing.T) {
+			var dst interface{}
+			if dstFunc := tc.Destination; dstFunc != nil {
+				dst = dstFunc()
+			}
+			err := blackmagic.AssignIfCompatible(dst, tc.Value)
+			if tc.Error {
+				if !assert.Error(t, err, `blackmagic.AssignIfCompatible should fail`) {
+					return
+				}
+			} else {
+				if !assert.NoError(t, err, `blackmagic.AssignIfCompatible should succeed`) {
+					return
+				}
+			}
+		})
+	}
+}

go.mod

@@ -0,0 +1,8 @@
+module github.com/lestrrat-go/blackmagic
+
+go 1.16
+
+require (
+	github.com/pkg/errors v0.9.1
+	github.com/stretchr/testify v1.7.0
+)

go.sum

@@ -0,0 +1,13 @@
+github.com/davecgh/go-spew v1.1.0 h1:ZDRjVQ15GmhC3fiQ8ni8+OwkZQO4DARzQgrnXU1Liz8=
+github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/pkg/errors v0.9.1 h1:FEBLx1zS214owpjy7qsBeixbURkuhQAwrK5UwLGTwt4=
+github.com/pkg/errors v0.9.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
+github.com/stretchr/testify v1.7.0 h1:nwc3DEeHmmLAfoZucVR881uASk0Mfjw8xYJ99tb5CcY=
+github.com/stretchr/testify v1.7.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c h1:dUUwHk2QECo/6vqA44rthZ8ie2QXMNeKRTHCNY2nXvo=
+gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=