DSCGS-36 Go mod updated, test updated (#38)

go.mod

@@ -1,5 +1,5 @@
 module github.com/irlndts/go-discogs
 
-go 1.13.4
+go 1.14
 
-require github.com/google/go-cmp v0.3.1
+require github.com/google/go-cmp v0.4.0

go.sum

@@ -1,2 +1,4 @@
-github.com/google/go-cmp v0.3.1 h1:Xye71clBPdm5HgqGwUkwhbynsUJZhDbS20FvLhQ2izg=
-github.com/google/go-cmp v0.3.1/go.mod h1:8QqcDgzrUqlUb/G2PQTWiueGozuR1884gddMywk6iLU=
+github.com/google/go-cmp v0.4.0 h1:xsAVV57WRhGj6kEIi8ReJzQlHHqcBYCElAvkovg3B/4=
+github.com/google/go-cmp v0.4.0/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
+golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543 h1:E7g+9GITq07hpfrRu66IVDexMakfv52eLZ2CXBWiKr4=
+golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=

models.go

@@ -22,7 +22,7 @@ type Series struct {
 	ID             int    `json:"id"`
 	Name           string `json:"name"`
 	ResourceURL    string `json:"resource_url"`
-	ThumbnailURL   string `json:"thumbnail_url"`
+	ThumbnailURL   string `json:"thumbnail_url,omitempty"`
 }
 
 // ArtistSource ...
@@ -68,7 +68,7 @@ type LabelSource struct {
 
 // Identifier ...
 type Identifier struct {
-	Description string `json:"description"`
+	Description string `json:"description,omitempty"`
 	Type        string `json:"type"`
 	Value       string `json:"value"`
 }

vendor/github.com/google/go-cmp/cmp/compare.go

@@ -22,8 +22,8 @@
 // equality is determined by recursively comparing the primitive kinds on both
 // values, much like reflect.DeepEqual. Unlike reflect.DeepEqual, unexported
 // fields are not compared by default; they result in panics unless suppressed
-// by using an Ignore option (see cmpopts.IgnoreUnexported) or explicitly compared
-// using the AllowUnexported option.
+// by using an Ignore option (see cmpopts.IgnoreUnexported) or explicitly
+// compared using the Exporter option.
 package cmp
 
 import (
@@ -62,8 +62,8 @@ import (
 //
 // Structs are equal if recursively calling Equal on all fields report equal.
 // If a struct contains unexported fields, Equal panics unless an Ignore option
-// (e.g., cmpopts.IgnoreUnexported) ignores that field or the AllowUnexported
-// option explicitly permits comparing the unexported field.
+// (e.g., cmpopts.IgnoreUnexported) ignores that field or the Exporter option
+// explicitly permits comparing the unexported field.
 //
 // Slices are equal if they are both nil or both non-nil, where recursively
 // calling Equal on all non-ignored slice or array elements report equal.
@@ -80,6 +80,11 @@ import (
 // Pointers and interfaces are equal if they are both nil or both non-nil,
 // where they have the same underlying concrete type and recursively
 // calling Equal on the underlying values reports equal.
+//
+// Before recursing into a pointer, slice element, or map, the current path
+// is checked to detect whether the address has already been visited.
+// If there is a cycle, then the pointed at values are considered equal
+// only if both addresses were previously visited in the same path step.
 func Equal(x, y interface{}, opts ...Option) bool {
 	vx := reflect.ValueOf(x)
 	vy := reflect.ValueOf(y)
@@ -137,6 +142,7 @@ type state struct {
 	// Calling statelessCompare must not result in observable changes to these.
 	result    diff.Result // The current result of comparison
 	curPath   Path        // The current path in the value tree
+	curPtrs   pointerPath // The current set of visited pointers
 	reporters []reporter  // Optional reporters
 
 	// recChecker checks for infinite cycles applying the same set of
@@ -148,13 +154,14 @@ type state struct {
 	dynChecker dynChecker
 
 	// These fields, once set by processOption, will not change.
-	exporters map[reflect.Type]bool // Set of structs with unexported field visibility
+	exporters []exporter // List of exporters for structs with unexported fields
 	opts      Options    // List of all fundamental and filter options
 }
 
 func newState(opts []Option) *state {
 	// Always ensure a validator option exists to validate the inputs.
 	s := &state{opts: Options{validator{}}}
+	s.curPtrs.Init()
 	s.processOption(Options(opts))
 	return s
 }
@@ -174,13 +181,8 @@ func (s *state) processOption(opt Option) {
 			panic(fmt.Sprintf("cannot use an unfiltered option: %v", opt))
 		}
 		s.opts = append(s.opts, opt)
-	case visibleStructs:
-		if s.exporters == nil {
-			s.exporters = make(map[reflect.Type]bool)
-		}
-		for t := range opt {
-			s.exporters[t] = true
-		}
+	case exporter:
+		s.exporters = append(s.exporters, opt)
 	case reporter:
 		s.reporters = append(s.reporters, opt)
 	default:
@@ -192,9 +194,9 @@ func (s *state) processOption(opt Option) {
 // This function is stateless in that it does not alter the current result,
 // or output to any registered reporters.
 func (s *state) statelessCompare(step PathStep) diff.Result {
-	// We do not save and restore the curPath because all of the compareX
-	// methods should properly push and pop from the path.
-	// It is an implementation bug if the contents of curPath differs from
+	// We do not save and restore curPath and curPtrs because all of the
+	// compareX methods should properly push and pop from them.
+	// It is an implementation bug if the contents of the paths differ from
 	// when calling this function to when returning from it.
 
 	oldResult, oldReporters := s.result, s.reporters
@@ -216,9 +218,17 @@ func (s *state) compareAny(step PathStep) {
 	}
 	s.recChecker.Check(s.curPath)
 
-	// Obtain the current type and values.
+	// Cycle-detection for slice elements (see NOTE in compareSlice).
 	t := step.Type()
 	vx, vy := step.Values()
+	if si, ok := step.(SliceIndex); ok && si.isSlice && vx.IsValid() && vy.IsValid() {
+		px, py := vx.Addr(), vy.Addr()
+		if eq, visited := s.curPtrs.Push(px, py); visited {
+			s.report(eq, reportByCycle)
+			return
+		}
+		defer s.curPtrs.Pop(px, py)
+	}
 
 	// Rule 1: Check whether an option applies on this node in the value tree.
 	if s.tryOptions(t, vx, vy) {
@@ -354,6 +364,7 @@ func sanitizeValue(v reflect.Value, t reflect.Type) reflect.Value {
 func (s *state) compareStruct(t reflect.Type, vx, vy reflect.Value) {
 	var vax, vay reflect.Value // Addressable versions of vx and vy
 
+	var mayForce, mayForceInit bool
 	step := StructField{&structField{}}
 	for i := 0; i < t.NumField(); i++ {
 		step.typ = t.Field(i).Type
@@ -375,7 +386,13 @@ func (s *state) compareStruct(t reflect.Type, vx, vy reflect.Value) {
 				vax = makeAddressable(vx)
 				vay = makeAddressable(vy)
 			}
-			step.mayForce = s.exporters[t]
+			if !mayForceInit {
+				for _, xf := range s.exporters {
+					mayForce = mayForce || xf(t)
+				}
+				mayForceInit = true
+			}
+			step.mayForce = mayForce
 			step.pvx = vax
 			step.pvy = vay
 			step.field = t.Field(i)
@@ -391,9 +408,21 @@ func (s *state) compareSlice(t reflect.Type, vx, vy reflect.Value) {
 		return
 	}
 
-	// TODO: Support cyclic data structures.
+	// NOTE: It is incorrect to call curPtrs.Push on the slice header pointer
+	// since slices represents a list of pointers, rather than a single pointer.
+	// The pointer checking logic must be handled on a per-element basis
+	// in compareAny.
+	//
+	// A slice header (see reflect.SliceHeader) in Go is a tuple of a starting
+	// pointer P, a length N, and a capacity C. Supposing each slice element has
+	// a memory size of M, then the slice is equivalent to the list of pointers:
+	//	[P+i*M for i in range(N)]
+	//
+	// For example, v[:0] and v[:1] are slices with the same starting pointer,
+	// but they are clearly different values. Using the slice pointer alone
+	// violates the assumption that equal pointers implies equal values.
 
-	step := SliceIndex{&sliceIndex{pathStep: pathStep{typ: t.Elem()}}}
+	step := SliceIndex{&sliceIndex{pathStep: pathStep{typ: t.Elem()}, isSlice: isSlice}}
 	withIndexes := func(ix, iy int) SliceIndex {
 		if ix >= 0 {
 			step.vx, step.xkey = vx.Index(ix), ix
@@ -470,7 +499,12 @@ func (s *state) compareMap(t reflect.Type, vx, vy reflect.Value) {
 		return
 	}
 
-	// TODO: Support cyclic data structures.
+	// Cycle-detection for maps.
+	if eq, visited := s.curPtrs.Push(vx, vy); visited {
+		s.report(eq, reportByCycle)
+		return
+	}
+	defer s.curPtrs.Pop(vx, vy)
 
 	// We combine and sort the two map keys so that we can perform the
 	// comparisons in a deterministic order.
@@ -507,7 +541,12 @@ func (s *state) comparePtr(t reflect.Type, vx, vy reflect.Value) {
 		return
 	}
 
-	// TODO: Support cyclic data structures.
+	// Cycle-detection for pointers.
+	if eq, visited := s.curPtrs.Push(vx, vy); visited {
+		s.report(eq, reportByCycle)
+		return
+	}
+	defer s.curPtrs.Pop(vx, vy)
 
 	vx, vy = vx.Elem(), vy.Elem()
 	s.compareAny(Indirect{&indirect{pathStep{t.Elem(), vx, vy}}})

vendor/github.com/google/go-cmp/cmp/export_panic.go

@@ -8,8 +8,8 @@ package cmp
 
 import "reflect"
 
-const supportAllowUnexported = false
+const supportExporters = false
 
 func retrieveUnexportedField(reflect.Value, reflect.StructField) reflect.Value {
-	panic("retrieveUnexportedField is not implemented")
+	panic("no support for forcibly accessing unexported fields")
 }

vendor/github.com/google/go-cmp/cmp/export_unsafe.go

@@ -11,7 +11,7 @@ import (
 	"unsafe"
 )
 
-const supportAllowUnexported = true
+const supportExporters = true
 
 // retrieveUnexportedField uses unsafe to forcibly retrieve any field from
 // a struct such that the value has read-write permissions.
@@ -19,5 +19,7 @@ const supportAllowUnexported = true
 // The parent struct, v, must be addressable, while f must be a StructField
 // describing the field to retrieve.
 func retrieveUnexportedField(v reflect.Value, f reflect.StructField) reflect.Value {
-	return reflect.NewAt(f.Type, unsafe.Pointer(v.UnsafeAddr()+f.Offset)).Elem()
+	// See https://github.com/google/go-cmp/issues/167 for discussion of the
+	// following expression.
+	return reflect.NewAt(f.Type, unsafe.Pointer(uintptr(unsafe.Pointer(v.UnsafeAddr()))+f.Offset)).Elem()
 }

vendor/github.com/google/go-cmp/cmp/options.go

@@ -225,8 +225,20 @@ func (validator) apply(s *state, vx, vy reflect.Value) {
 
 	// Unable to Interface implies unexported field without visibility access.
 	if !vx.CanInterface() || !vy.CanInterface() {
-		const help = "consider using a custom Comparer; if you control the implementation of type, you can also consider AllowUnexported or cmpopts.IgnoreUnexported"
-		panic(fmt.Sprintf("cannot handle unexported field: %#v\n%s", s.curPath, help))
+		const help = "consider using a custom Comparer; if you control the implementation of type, you can also consider using an Exporter, AllowUnexported, or cmpopts.IgnoreUnexported"
+		var name string
+		if t := s.curPath.Index(-2).Type(); t.Name() != "" {
+			// Named type with unexported fields.
+			name = fmt.Sprintf("%q.%v", t.PkgPath(), t.Name()) // e.g., "path/to/package".MyType
+		} else {
+			// Unnamed type with unexported fields. Derive PkgPath from field.
+			var pkgPath string
+			for i := 0; i < t.NumField() && pkgPath == ""; i++ {
+				pkgPath = t.Field(i).PkgPath
+			}
+			name = fmt.Sprintf("%q.(%v)", pkgPath, t.String()) // e.g., "path/to/package".(struct { a int })
+		}
+		panic(fmt.Sprintf("cannot handle unexported field at %#v:\n\t%v\n%s", s.curPath, name, help))
 	}
 
 	panic("not reachable")
@@ -360,9 +372,8 @@ func (cm comparer) String() string {
 	return fmt.Sprintf("Comparer(%s)", function.NameOf(cm.fnc))
 }
 
-// AllowUnexported returns an Option that forcibly allows operations on
-// unexported fields in certain structs, which are specified by passing in a
-// value of each struct type.
+// Exporter returns an Option that specifies whether Equal is allowed to
+// introspect into the unexported fields of certain struct types.
 //
 // Users of this option must understand that comparing on unexported fields
 // from external packages is not safe since changes in the internal
@@ -386,10 +397,24 @@ func (cm comparer) String() string {
 //
 // In other cases, the cmpopts.IgnoreUnexported option can be used to ignore
 // all unexported fields on specified struct types.
-func AllowUnexported(types ...interface{}) Option {
-	if !supportAllowUnexported {
-		panic("AllowUnexported is not supported on purego builds, Google App Engine Standard, or GopherJS")
+func Exporter(f func(reflect.Type) bool) Option {
+	if !supportExporters {
+		panic("Exporter is not supported on purego builds")
 	}
+	return exporter(f)
+}
+
+type exporter func(reflect.Type) bool
+
+func (exporter) filter(_ *state, _ reflect.Type, _, _ reflect.Value) applicableOption {
+	panic("not implemented")
+}
+
+// AllowUnexported returns an Options that allows Equal to forcibly introspect
+// unexported fields of the specified struct types.
+//
+// See Exporter for the proper use of this option.
+func AllowUnexported(types ...interface{}) Option {
 	m := make(map[reflect.Type]bool)
 	for _, typ := range types {
 		t := reflect.TypeOf(typ)
@@ -398,13 +423,7 @@ func AllowUnexported(types ...interface{}) Option {
 		}
 		m[t] = true
 	}
-	return visibleStructs(m)
-}
-
-type visibleStructs map[reflect.Type]bool
-
-func (visibleStructs) filter(_ *state, _ reflect.Type, _, _ reflect.Value) applicableOption {
-	panic("not implemented")
+	return exporter(func(t reflect.Type) bool { return m[t] })
 }
 
 // Result represents the comparison result for a single node and
@@ -436,6 +455,11 @@ func (r Result) ByFunc() bool {
 	return r.flags&reportByFunc != 0
 }
 
+// ByCycle reports whether a reference cycle was detected.
+func (r Result) ByCycle() bool {
+	return r.flags&reportByCycle != 0
+}
+
 type resultFlags uint
 
 const (
@@ -446,6 +470,7 @@ const (
 	reportByIgnore
 	reportByMethod
 	reportByFunc
+	reportByCycle
 )
 
 // Reporter is an Option that can be passed to Equal. When Equal traverses

vendor/github.com/google/go-cmp/cmp/path.go

@@ -10,6 +10,8 @@ import (
 	"strings"
 	"unicode"
 	"unicode/utf8"
+
+	"github.com/google/go-cmp/cmp/internal/value"
 )
 
 // Path is a list of PathSteps describing the sequence of operations to get
@@ -41,7 +43,7 @@ type PathStep interface {
 	// In some cases, one or both may be invalid or have restrictions:
 	//	• For StructField, both are not interface-able if the current field
 	//	is unexported and the struct type is not explicitly permitted by
-	//	AllowUnexported to traverse unexported fields.
+	//	an Exporter to traverse unexported fields.
 	//	• For SliceIndex, one may be invalid if an element is missing from
 	//	either the x or y slice.
 	//	• For MapIndex, one may be invalid if an entry is missing from
@@ -207,6 +209,7 @@ type SliceIndex struct{ *sliceIndex }
 type sliceIndex struct {
 	pathStep
 	xkey, ykey int
+	isSlice    bool // False for reflect.Array
 }
 
 func (si SliceIndex) Type() reflect.Type             { return si.typ }
@@ -301,6 +304,72 @@ func (tf Transform) Func() reflect.Value { return tf.trans.fnc }
 // The == operator can be used to detect the exact option used.
 func (tf Transform) Option() Option { return tf.trans }
 
+// pointerPath represents a dual-stack of pointers encountered when
+// recursively traversing the x and y values. This data structure supports
+// detection of cycles and determining whether the cycles are equal.
+// In Go, cycles can occur via pointers, slices, and maps.
+//
+// The pointerPath uses a map to represent a stack; where descension into a
+// pointer pushes the address onto the stack, and ascension from a pointer
+// pops the address from the stack. Thus, when traversing into a pointer from
+// reflect.Ptr, reflect.Slice element, or reflect.Map, we can detect cycles
+// by checking whether the pointer has already been visited. The cycle detection
+// uses a seperate stack for the x and y values.
+//
+// If a cycle is detected we need to determine whether the two pointers
+// should be considered equal. The definition of equality chosen by Equal
+// requires two graphs to have the same structure. To determine this, both the
+// x and y values must have a cycle where the previous pointers were also
+// encountered together as a pair.
+//
+// Semantically, this is equivalent to augmenting Indirect, SliceIndex, and
+// MapIndex with pointer information for the x and y values.
+// Suppose px and py are two pointers to compare, we then search the
+// Path for whether px was ever encountered in the Path history of x, and
+// similarly so with py. If either side has a cycle, the comparison is only
+// equal if both px and py have a cycle resulting from the same PathStep.
+//
+// Using a map as a stack is more performant as we can perform cycle detection
+// in O(1) instead of O(N) where N is len(Path).
+type pointerPath struct {
+	// mx is keyed by x pointers, where the value is the associated y pointer.
+	mx map[value.Pointer]value.Pointer
+	// my is keyed by y pointers, where the value is the associated x pointer.
+	my map[value.Pointer]value.Pointer
+}
+
+func (p *pointerPath) Init() {
+	p.mx = make(map[value.Pointer]value.Pointer)
+	p.my = make(map[value.Pointer]value.Pointer)
+}
+
+// Push indicates intent to descend into pointers vx and vy where
+// visited reports whether either has been seen before. If visited before,
+// equal reports whether both pointers were encountered together.
+// Pop must be called if and only if the pointers were never visited.
+//
+// The pointers vx and vy must be a reflect.Ptr, reflect.Slice, or reflect.Map
+// and be non-nil.
+func (p pointerPath) Push(vx, vy reflect.Value) (equal, visited bool) {
+	px := value.PointerOf(vx)
+	py := value.PointerOf(vy)
+	_, ok1 := p.mx[px]
+	_, ok2 := p.my[py]
+	if ok1 || ok2 {
+		equal = p.mx[px] == py && p.my[py] == px // Pointers paired together
+		return equal, true
+	}
+	p.mx[px] = py
+	p.my[py] = px
+	return false, false
+}
+
+// Pop ascends from pointers vx and vy.
+func (p pointerPath) Pop(vx, vy reflect.Value) {
+	delete(p.mx, value.PointerOf(vx))
+	delete(p.my, value.PointerOf(vy))
+}
+
 // isExported reports whether the identifier is exported.
 func isExported(id string) bool {
 	r, _ := utf8.DecodeRuneInString(id)

vendor/modules.txt

@@ -1,4 +1,5 @@
-# github.com/google/go-cmp v0.3.1
+# github.com/google/go-cmp v0.4.0
+## explicit
 github.com/google/go-cmp/cmp
 github.com/google/go-cmp/cmp/internal/diff
 github.com/google/go-cmp/cmp/internal/flags