multi: update blockchain/standalone error types.

This updates the standalone error types to leverage go
1.13 errors.Is/As functionality as well as conform
to the error infrastructure best practices.

blockchain/standalone/error.go

@@ -4,73 +4,55 @@
 
 package standalone
 
-import (
-	"fmt"
-)
-
-// ErrorCode identifies a kind of error.
-type ErrorCode int
+// ErrorKind identifies a kind of error.  It has full support for errors.Is and
+// errors.As, so the caller can directly check against an error kind when
+// determining the reason for an error.
+type ErrorKind string
 
 // These constants are used to identify a specific RuleError.
 const (
 	// ErrUnexpectedDifficulty indicates specified bits do not align with
 	// the expected value either because it doesn't match the calculated
 	// value based on difficulty rules or it is out of the valid range.
-	ErrUnexpectedDifficulty ErrorCode = iota
+	ErrUnexpectedDifficulty = ErrorKind("ErrUnexpectedDifficulty")
 
 	// ErrHighHash indicates the block does not hash to a value which is
 	// lower than the required target difficultly.
-	ErrHighHash
+	ErrHighHash = ErrorKind("ErrHighHash")
 
 	// ErrTSpendStartInvalidExpiry indicates that an invalid expiry was
 	// provided to calculate the start of a treasury spend vote window.
-	ErrTSpendStartInvalidExpiry
+	ErrTSpendStartInvalidExpiry = ErrorKind("ErrTSpendStartInvalidExpiry")
 
 	// ErrTSpendEndInvalidExpiry indicates that an invalid expiry was
 	// provided to calculate the end of a treasury spend vote window.
-	ErrTSpendEndInvalidExpiry
-
-	// numErrorCodes is the maximum error code number used in tests.
-	numErrorCodes
+	ErrTSpendEndInvalidExpiry = ErrorKind("ErrTSpendEndInvalidExpiry")
 )
 
-// Map of ErrorCode values back to their constant names for pretty printing.
-var errorCodeStrings = map[ErrorCode]string{
-	ErrUnexpectedDifficulty:     "ErrUnexpectedDifficulty",
-	ErrHighHash:                 "ErrHighHash",
-	ErrTSpendStartInvalidExpiry: "ErrTSpendStartInvalidExpiry",
-	ErrTSpendEndInvalidExpiry:   "ErrTSpendEndInvalidExpiry",
-}
-
-// String returns the ErrorCode as a human-readable name.
-func (e ErrorCode) String() string {
-	if s := errorCodeStrings[e]; s != "" {
-		return s
-	}
-	return fmt.Sprintf("Unknown ErrorCode (%d)", int(e))
+// Error satisfies the error interface and prints human-readable errors.
+func (e ErrorKind) Error() string {
+	return string(e)
 }
 
-// RuleError identifies a rule violation.  The caller can use type assertions to
-// determine if a failure was specifically due to a rule violation and access
-// the ErrorCode field to ascertain the specific reason for the rule violation.
+// RuleError identifies a rule violation. It has full support for errors.Is
+// and errors.As, so the caller can ascertain the specific reason for the
+// error by checking the underlying error.
 type RuleError struct {
-	ErrorCode   ErrorCode // Describes the kind of error
-	Description string    // Human readable description of the issue
+	Description string
+	Err         error
 }
 
 // Error satisfies the error interface and prints human-readable errors.
 func (e RuleError) Error() string {
 	return e.Description
 }
 
-// ruleError creates an RuleError given a set of arguments.
-func ruleError(c ErrorCode, desc string) RuleError {
-	return RuleError{ErrorCode: c, Description: desc}
+// Unwrap returns the underlying wrapped error.
+func (e RuleError) Unwrap() error {
+	return e.Err
 }
 
-// IsErrorCode returns whether or not the provided error is a rule error with
-// the provided error code.
-func IsErrorCode(err error, c ErrorCode) bool {
-	e, ok := err.(RuleError)
-	return ok && e.ErrorCode == c
+// ruleError creates a RuleError given a set of arguments.
+func ruleError(kind ErrorKind, desc string) RuleError {
+	return RuleError{Err: kind, Description: desc}
 }

blockchain/standalone/error_test.go

@@ -5,33 +5,28 @@
 package standalone
 
 import (
+	"errors"
+	"io"
 	"testing"
 )
 
-// TestErrorCodeStringer tests the stringized output for the ErrorCode type.
-func TestErrorCodeStringer(t *testing.T) {
+// TestErrorKindStringer tests the stringized output for the ErrorKind type.
+func TestErrorKindStringer(t *testing.T) {
 	tests := []struct {
-		in   ErrorCode
+		in   ErrorKind
 		want string
 	}{
 		{ErrUnexpectedDifficulty, "ErrUnexpectedDifficulty"},
 		{ErrHighHash, "ErrHighHash"},
 		{ErrTSpendStartInvalidExpiry, "ErrTSpendStartInvalidExpiry"},
 		{ErrTSpendEndInvalidExpiry, "ErrTSpendEndInvalidExpiry"},
-		{0xffff, "Unknown ErrorCode (65535)"},
-	}
-
-	// Detect additional error codes that don't have the stringer added.
-	if len(tests)-1 != int(numErrorCodes) {
-		t.Errorf("It appears an error code was added without adding an " +
-			"associated stringer test")
 	}
 
 	t.Logf("Running %d tests", len(tests))
 	for i, test := range tests {
-		result := test.in.String()
+		result := test.in.Error()
 		if result != test.want {
-			t.Errorf("String #%d\n got: %s want: %s", i, result, test.want)
+			t.Errorf("%d: got: %s want: %s", i, result, test.want)
 			continue
 		}
 	}
@@ -43,8 +38,8 @@ func TestRuleError(t *testing.T) {
 		in   RuleError
 		want string
 	}{{
-		RuleError{Description: "duplicate block"},
-		"duplicate block",
+		RuleError{Description: "unexpected difficulty"},
+		"unexpected difficulty",
 	}, {
 		RuleError{Description: "human-readable error"},
 		"human-readable error",
@@ -55,50 +50,91 @@ func TestRuleError(t *testing.T) {
 	for i, test := range tests {
 		result := test.in.Error()
 		if result != test.want {
-			t.Errorf("Error #%d\n got: %s want: %s", i, result, test.want)
+			t.Errorf("%d: got: %s want: %s", i, result, test.want)
 			continue
 		}
 	}
 }
 
-// TestIsErrorCode ensures IsErrorCode works as intended.
-func TestIsErrorCode(t *testing.T) {
+// TestRuleErrorKindIsAs ensures both ErrorKind and RuleError can be
+// identified as being a specific error kind via errors.Is and unwrapped
+// via errors.As.
+func TestRuleErrorKindIsAs(t *testing.T) {
 	tests := []struct {
-		name string
-		err  error
-		code ErrorCode
-		want bool
+		name      string
+		err       error
+		target    error
+		wantMatch bool
+		wantAs    ErrorKind
 	}{{
-		name: "ErrUnexpectedDifficulty testing for ErrUnexpectedDifficulty",
-		err:  ruleError(ErrUnexpectedDifficulty, ""),
-		code: ErrUnexpectedDifficulty,
-		want: true,
+		name:      "ErrUnexpectedDifficulty == ErrUnexpectedDifficulty",
+		err:       ErrUnexpectedDifficulty,
+		target:    ErrUnexpectedDifficulty,
+		wantMatch: true,
+		wantAs:    ErrUnexpectedDifficulty,
+	}, {
+		name:      "RuleError.ErrUnexpectedDifficulty == ErrUnexpectedDifficulty",
+		err:       ruleError(ErrUnexpectedDifficulty, ""),
+		target:    ErrUnexpectedDifficulty,
+		wantMatch: true,
+		wantAs:    ErrUnexpectedDifficulty,
 	}, {
-		name: "ErrHighHash testing for ErrHighHash",
-		err:  ruleError(ErrHighHash, ""),
-		code: ErrHighHash,
-		want: true,
+		name:      "RuleError.ErrUnexpectedDifficulty == RuleError.ErrUnexpectedDifficulty",
+		err:       ruleError(ErrUnexpectedDifficulty, ""),
+		target:    ruleError(ErrUnexpectedDifficulty, ""),
+		wantMatch: true,
+		wantAs:    ErrUnexpectedDifficulty,
 	}, {
-		name: "ErrHighHash error testing for ErrUnexpectedDifficulty",
-		err:  ruleError(ErrHighHash, ""),
-		code: ErrUnexpectedDifficulty,
-		want: false,
+		name:      "ErrUnexpectedDifficulty != ErrHighHash",
+		err:       ErrUnexpectedDifficulty,
+		target:    ErrHighHash,
+		wantMatch: false,
+		wantAs:    ErrUnexpectedDifficulty,
 	}, {
-		name: "ErrHighHash error testing for unknown error code",
-		err:  ruleError(ErrHighHash, ""),
-		code: 0xffff,
-		want: false,
+		name:      "RuleError.ErrUnexpectedDifficulty != ErrHighHash",
+		err:       ruleError(ErrUnexpectedDifficulty, ""),
+		target:    ErrHighHash,
+		wantMatch: false,
+		wantAs:    ErrUnexpectedDifficulty,
 	}, {
-		name: "nil error testing for ErrUnexpectedDifficulty",
-		err:  nil,
-		code: ErrUnexpectedDifficulty,
-		want: false,
+		name:      "ErrUnexpectedDifficulty != RuleError.ErrHighHash",
+		err:       ErrUnexpectedDifficulty,
+		target:    ruleError(ErrHighHash, ""),
+		wantMatch: false,
+		wantAs:    ErrUnexpectedDifficulty,
+	}, {
+		name:      "RuleError.ErrUnexpectedDifficulty != RuleError.ErrHighHash",
+		err:       ruleError(ErrUnexpectedDifficulty, ""),
+		target:    ruleError(ErrHighHash, ""),
+		wantMatch: false,
+		wantAs:    ErrUnexpectedDifficulty,
+	}, {
+		name:      "RuleError.ErrUnexpectedDifficulty != io.EOF",
+		err:       ruleError(ErrUnexpectedDifficulty, ""),
+		target:    io.EOF,
+		wantMatch: false,
+		wantAs:    ErrUnexpectedDifficulty,
 	}}
+
 	for _, test := range tests {
-		result := IsErrorCode(test.err, test.code)
-		if result != test.want {
-			t.Errorf("%s: unexpected result -- got: %v want: %v", test.name,
-				result, test.want)
+		// Ensure the error matches or not depending on the expected result.
+		result := errors.Is(test.err, test.target)
+		if result != test.wantMatch {
+			t.Errorf("%s: incorrect error identification -- got %v, want %v",
+				test.name, result, test.wantMatch)
+			continue
+		}
+
+		// Ensure the underlying error kind can be unwrapped is and is the
+		// expected kind.
+		var kind ErrorKind
+		if !errors.As(test.err, &kind) {
+			t.Errorf("%s: unable to unwrap to error kind", test.name)
+			continue
+		}
+		if kind != test.wantAs {
+			t.Errorf("%s: unexpected unwrapped error kind -- got %v, want %v",
+				test.name, kind, test.wantAs)
 			continue
 		}
 	}

blockchain/standalone/pow_test.go

@@ -5,6 +5,7 @@
 package standalone
 
 import (
+	"errors"
 	"math/big"
 	"testing"
 
@@ -248,17 +249,17 @@ func TestCheckProofOfWorkRange(t *testing.T) {
 		name:     "zero",
 		bits:     0,
 		powLimit: mockMainNetPowLimit(),
-		err:      ruleError(ErrUnexpectedDifficulty, ""),
+		err:      ErrUnexpectedDifficulty,
 	}, {
 		name:     "negative",
 		bits:     0x1810000,
 		powLimit: mockMainNetPowLimit(),
-		err:      ruleError(ErrUnexpectedDifficulty, ""),
+		err:      ErrUnexpectedDifficulty,
 	}, {
 		name:     "pow limit + 1",
 		bits:     0x1d010000,
 		powLimit: mockMainNetPowLimit(),
-		err:      ruleError(ErrUnexpectedDifficulty, ""),
+		err:      ErrUnexpectedDifficulty,
 	}}
 
 	for _, test := range tests {
@@ -269,15 +270,9 @@ func TestCheckProofOfWorkRange(t *testing.T) {
 		}
 
 		err := CheckProofOfWorkRange(test.bits, powLimit)
-		if test.err == nil && err != nil {
-			t.Errorf("%q: unexpected err -- got %v, want nil", test.name, err)
-			continue
-		} else if test.err != nil {
-			if !IsErrorCode(err, test.err.(RuleError).ErrorCode) {
-				t.Errorf("%q: unexpected err -- got %v, want %v",
-					test.name, err, test.err.(RuleError).ErrorCode)
-				continue
-			}
+		if !errors.Is(err, test.err) {
+			t.Errorf("%q: unexpected err -- got %v, want %v", test.name, err,
+				test.err)
 			continue
 		}
 	}
@@ -316,25 +311,25 @@ func TestCheckProofOfWork(t *testing.T) {
 		hash:     "000000000001ffff000000000000000000000000000000000000000000000001",
 		bits:     0x1b01ffff,
 		powLimit: mockMainNetPowLimit(),
-		err:      ruleError(ErrHighHash, ""),
+		err:      ErrHighHash,
 	}, {
 		name:     "hash satisfies target, but target too high at pow limit + 1",
 		hash:     "0000000000000000000000000000000000000000000000000000000000000001",
 		bits:     0x1d010000,
 		powLimit: mockMainNetPowLimit(),
-		err:      ruleError(ErrUnexpectedDifficulty, ""),
+		err:      ErrUnexpectedDifficulty,
 	}, {
 		name:     "zero target difficulty",
 		hash:     "0000000000000000000000000000000000000000000000000000000000000001",
 		bits:     0,
 		powLimit: mockMainNetPowLimit(),
-		err:      ruleError(ErrUnexpectedDifficulty, ""),
+		err:      ErrUnexpectedDifficulty,
 	}, {
 		name:     "negative target difficulty",
 		hash:     "0000000000000000000000000000000000000000000000000000000000000001",
 		bits:     0x1810000,
 		powLimit: mockMainNetPowLimit(),
-		err:      ruleError(ErrUnexpectedDifficulty, ""),
+		err:      ErrUnexpectedDifficulty,
 	}}
 
 	for _, test := range tests {
@@ -351,15 +346,9 @@ func TestCheckProofOfWork(t *testing.T) {
 		}
 
 		err = CheckProofOfWork(hash, test.bits, powLimit)
-		if test.err == nil && err != nil {
-			t.Errorf("%q: unexpected err -- got %v, want nil", test.name, err)
-			continue
-		} else if test.err != nil {
-			if !IsErrorCode(err, test.err.(RuleError).ErrorCode) {
-				t.Errorf("%q: unexpected err -- got %v, want %v",
-					test.name, err, test.err.(RuleError).ErrorCode)
-				continue
-			}
+		if !errors.Is(err, test.err) {
+			t.Errorf("%q: unexpected err -- got %v, want %v", test.name, err,
+				test.err)
 			continue
 		}
 	}

blockchain/standalone/treasury.go

@@ -29,8 +29,8 @@ func IsTreasuryVoteInterval(height, tvi uint64) bool {
 // this function is only called with an expiry that *IS* on a TVI.
 func CalculateTSpendWindowStart(expiry uint32, tvi, multiplier uint64) (uint32, error) {
 	if !IsTreasuryVoteInterval(uint64(expiry-2), tvi) {
-		return 0, RuleError{ErrTSpendStartInvalidExpiry,
-			fmt.Sprintf("invalid start expiry: %v", expiry)}
+		return 0, ruleError(ErrTSpendStartInvalidExpiry,
+			fmt.Sprintf("invalid start expiry: %v", expiry))
 	}
 	return expiry - uint32(tvi*multiplier) - 2, nil
 }
@@ -40,8 +40,8 @@ func CalculateTSpendWindowStart(expiry uint32, tvi, multiplier uint64) (uint32,
 // this function is only called with an expiry that *IS* on a TVI.
 func CalculateTSpendWindowEnd(expiry uint32, tvi uint64) (uint32, error) {
 	if !IsTreasuryVoteInterval(uint64(expiry-2), tvi) {
-		return 0, RuleError{ErrTSpendEndInvalidExpiry,
-			fmt.Sprintf("invalid end expiry: %v", expiry)}
+		return 0, ruleError(ErrTSpendEndInvalidExpiry,
+			fmt.Sprintf("invalid end expiry: %v", expiry))
 	}
 	return expiry - 2, nil
 }