blockchain/stake: update error types.

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

blockchain/stake/error.go

@@ -1,255 +1,205 @@
 // Copyright (c) 2014 Conformal Systems LLC.
-// Copyright (c) 2015-2016 The Decred developers
+// Copyright (c) 2015-2020 The Decred developers
 // Use of this source code is governed by an ISC
 // license that can be found in the LICENSE file.
 
 package stake
 
-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 (
 	// ErrSStxTooManyInputs indicates that a given SStx contains too many
 	// inputs.
-	ErrSStxTooManyInputs = iota
+	ErrSStxTooManyInputs = ErrorKind("ErrSStxTooManyInputs")
 
 	// ErrSStxTooManyOutputs indicates that a given SStx contains too many
 	// outputs.
-	ErrSStxTooManyOutputs
+	ErrSStxTooManyOutputs = ErrorKind("ErrSStxTooManyOutputs")
 
 	// ErrSStxNoOutputs indicates that a given SStx has no outputs.
-	ErrSStxNoOutputs
+	ErrSStxNoOutputs = ErrorKind("ErrSStxNoOutputs")
 
 	// ErrSStxInvalidInput indicates that an invalid output has been used as
 	// an input for a SStx; only non-SStx tagged outputs may be used to
 	// purchase stake tickets.
 	// TODO: Add this into validate
 	// Ensure that all inputs are not tagged SStx outputs of some sort,
 	// along with checks to make sure they exist and are available.
-	ErrSStxInvalidInputs
+	ErrSStxInvalidInputs = ErrorKind("ErrSStxInvalidInputs")
 
 	// ErrSStxInvalidOutput indicates that the output for an SStx tx is
 	// invalid; in particular, either the output was not tagged SStx or the
 	// OP_RETURNs were missing or contained invalid addresses.
-	ErrSStxInvalidOutputs
+	ErrSStxInvalidOutputs = ErrorKind("ErrSStxInvalidOutputs")
 
 	// ErrSStxInOutProportions indicates the number of inputs in an SStx
 	// was not equal to the number of output minus one.
-	ErrSStxInOutProportions
+	ErrSStxInOutProportions = ErrorKind("ErrSStxInOutProportions")
 
 	// ErrSStxBadCommitAmount indicates that a ticket tried to commit 0 or
 	// a negative value as the commitment amount.
-	ErrSStxBadCommitAmount
+	ErrSStxBadCommitAmount = ErrorKind("ErrSStxBadCommitAmount")
 
 	// ErrSStxBadChangeAmts indicates that the change amount for some SStx
 	// was invalid, for instance spending more than its inputs.
-	ErrSStxBadChangeAmts
+	ErrSStxBadChangeAmts = ErrorKind("ErrSStxBadChangeAmts")
 
 	// ErrSStxVerifyCalcAmts indicates that passed calculated amounts failed
 	// to conform to the amounts found in the ticket.
-	ErrSStxVerifyCalcAmts
+	ErrSStxVerifyCalcAmts = ErrorKind("ErrSStxVerifyCalcAmts")
 
 	// ErrSSGenWrongNumInputs indicates that a given SSGen tx contains an
 	// invalid number of inputs.
-	ErrSSGenWrongNumInputs
+	ErrSSGenWrongNumInputs = ErrorKind("ErrSSGenWrongNumInputs")
 
 	// ErrSSGenTooManyOutputs indicates that a given SSGen tx contains too
 	// many outputs.
-	ErrSSGenTooManyOutputs
+	ErrSSGenTooManyOutputs = ErrorKind("ErrSSGenTooManyOutputs")
 
 	// ErrSSGenNoOutputs indicates that a given SSGen has no outputs.
-	ErrSSGenNoOutputs
+	ErrSSGenNoOutputs = ErrorKind("ErrSSGenNoOutputs")
 
 	// ErrSSGenWrongIndex indicates that a given SSGen sstx input was not
 	// using the correct index.
-	ErrSSGenWrongIndex
+	ErrSSGenWrongIndex = ErrorKind("ErrSSGenWrongIndex")
 
 	// ErrSSGenWrongTxTree indicates that a given SSGen tx input was not found in
 	// the stake tx tree.
-	ErrSSGenWrongTxTree
+	ErrSSGenWrongTxTree = ErrorKind("ErrSSGenWrongTxTree")
 
 	// ErrSSGenNoStakebase indicates that the SSGen tx did not contain a
 	// valid StakeBase in the zeroeth position of inputs.
-	ErrSSGenNoStakebase
+	ErrSSGenNoStakebase = ErrorKind("ErrSSGenNoStakebase")
 
 	// ErrSSGenNoReference indicates that there is no reference OP_RETURN
 	// included as the first output.
-	ErrSSGenNoReference
+	ErrSSGenNoReference = ErrorKind("ErrSSGenNoReference")
 
 	// ErrSSGenNoReference indicates that the OP_RETURN included as the
 	// first output was corrupted in some way.
-	ErrSSGenBadReference
+	ErrSSGenBadReference = ErrorKind("ErrSSGenBadReference")
 
 	// ErrSSGenNoVotePush indicates that there is no vote bits OP_RETURN
 	// included as the second output.
-	ErrSSGenNoVotePush
+	ErrSSGenNoVotePush = ErrorKind("ErrSSGenNoVotePush")
 
 	// ErrSSGenBadVotePush indicates that the OP_RETURN included as the
 	// second output was corrupted in some way.
-	ErrSSGenBadVotePush
+	ErrSSGenBadVotePush = ErrorKind("ErrSSGenBadVotePush")
 
 	// ErrSSGenBadGenOuts indicates that the something was wrong with the
 	// stake generation outputs that were present after the first two
 	// OP_RETURN pushes in an SSGen tx.
-	ErrSSGenBadGenOuts
+	ErrSSGenBadGenOuts = ErrorKind("ErrSSGenBadGenOuts")
 
 	// ErrSSRtxWrongNumInputs indicates that a given SSRtx contains an
 	// invalid number of inputs.
-	ErrSSRtxWrongNumInputs
+	ErrSSRtxWrongNumInputs = ErrorKind("ErrSSRtxWrongNumInputs")
 
 	// ErrSSRtxTooManyOutputs indicates that a given SSRtx contains too many
 	// outputs.
-	ErrSSRtxTooManyOutputs
+	ErrSSRtxTooManyOutputs = ErrorKind("ErrSSRtxTooManyOutputs")
 
 	// ErrSSRtxNoOutputs indicates that a given SSRtx has no outputs.
-	ErrSSRtxNoOutputs
+	ErrSSRtxNoOutputs = ErrorKind("ErrSSRtxNoOutputs")
 
 	// ErrSSRtxWrongTxTree indicates that a given SSRtx input was not found in
 	// the stake tx tree.
-	ErrSSRtxWrongTxTree
+	ErrSSRtxWrongTxTree = ErrorKind("ErrSSRtxWrongTxTree")
 
 	// ErrSSRtxBadGenOuts indicates that there was a non-SSRtx tagged output
 	// present in an SSRtx.
-	ErrSSRtxBadOuts
+	ErrSSRtxBadOuts = ErrorKind("ErrSSRtxBadOuts")
 
 	// ErrVerSStxAmts indicates there was an error verifying the calculated
 	// SStx out amounts and the actual SStx out amounts.
-	ErrVerSStxAmts
+	ErrVerSStxAmts = ErrorKind("ErrVerSStxAmts")
 
 	// ErrVerifyInput indicates that there was an error in verification
 	// function input.
-	ErrVerifyInput
+	ErrVerifyInput = ErrorKind("ErrVerifyInput")
 
 	// ErrVerifyOutType indicates that there was a non-equivalence in the
 	// output type.
-	ErrVerifyOutType
+	ErrVerifyOutType = ErrorKind("ErrVerifyOutType")
 
 	// ErrVerifyTooMuchFees indicates that a transaction's output gave
 	// too much in fees after taking into accounts the limits imposed
 	// by the SStx output's version field.
-	ErrVerifyTooMuchFees
+	ErrVerifyTooMuchFees = ErrorKind("ErrVerifyTooMuchFees")
 
 	// ErrVerifySpendTooMuch indicates that a transaction's output spent more
 	// than it was allowed to spend based on the calculated subsidy or return
 	// for a vote or revocation.
-	ErrVerifySpendTooMuch
+	ErrVerifySpendTooMuch = ErrorKind("ErrVerifySpendTooMuch")
 
 	// ErrVerifyOutputAmt indicates that for a vote/revocation spend output,
 	// the rule was given that it must exactly match the calculated maximum,
 	// however the amount in the output did not (e.g. it gave fees).
-	ErrVerifyOutputAmt
+	ErrVerifyOutputAmt = ErrorKind("ErrVerifyOutputAmt")
 
 	// ErrVerifyOutPkhs indicates that the recipient of the P2PKH or P2SH
 	// script was different from that indicated in the SStx input.
-	ErrVerifyOutPkhs
+	ErrVerifyOutPkhs = ErrorKind("ErrVerifyOutPkhs")
 
 	// ErrDatabaseCorrupt indicates a database inconsistency.
-	ErrDatabaseCorrupt
+	ErrDatabaseCorrupt = ErrorKind("ErrDatabaseCorrupt")
 
 	// ErrMissingDatabaseTx indicates that a node disconnection failed to
 	// pass a database transaction when attempted to remove a very old
 	// node.
-	ErrMissingDatabaseTx
+	ErrMissingDatabaseTx = ErrorKind("ErrMissingDatabaseTx")
 
 	// ErrMemoryCorruption indicates that memory has somehow become corrupt,
 	// for example invalid block header serialization from an in memory
 	// struct.
-	ErrMemoryCorruption
+	ErrMemoryCorruption = ErrorKind("ErrMemoryCorruption")
 
 	// ErrFindTicketIdxs indicates a failure to find the selected ticket
 	// indexes from the block header.
-	ErrFindTicketIdxs
+	ErrFindTicketIdxs = ErrorKind("ErrFindTicketIdxs")
 
 	// ErrMissingTicket indicates that a ticket was missing in one of the
 	// ticket treaps when it was attempted to be fetched.
-	ErrMissingTicket
+	ErrMissingTicket = ErrorKind("ErrMissingTicket")
 
 	// ErrDuplicateTicket indicates that a duplicate ticket was attempted
 	// to be inserted into a ticket treap or the database.
-	ErrDuplicateTicket
+	ErrDuplicateTicket = ErrorKind("ErrDuplicateTicket")
 
 	// ErrUnknownTicketSpent indicates that an unknown ticket was spent by
 	// the block.
-	ErrUnknownTicketSpent
+	ErrUnknownTicketSpent = ErrorKind("ErrUnknownTicketSpent")
 )
 
-// Map of ErrorCode values back to their constant names for pretty printing.
-var errorCodeStrings = map[ErrorCode]string{
-	ErrSStxTooManyInputs:    "ErrSStxTooManyInputs",
-	ErrSStxTooManyOutputs:   "ErrSStxTooManyOutputs",
-	ErrSStxNoOutputs:        "ErrSStxNoOutputs",
-	ErrSStxInvalidInputs:    "ErrSStxInvalidInputs",
-	ErrSStxInvalidOutputs:   "ErrSStxInvalidOutputs",
-	ErrSStxInOutProportions: "ErrSStxInOutProportions",
-	ErrSStxBadCommitAmount:  "ErrSStxBadCommitAmount",
-	ErrSStxBadChangeAmts:    "ErrSStxBadChangeAmts",
-	ErrSStxVerifyCalcAmts:   "ErrSStxVerifyCalcAmts",
-	ErrSSGenWrongNumInputs:  "ErrSSGenWrongNumInputs",
-	ErrSSGenTooManyOutputs:  "ErrSSGenTooManyOutputs",
-	ErrSSGenNoOutputs:       "ErrSSGenNoOutputs",
-	ErrSSGenWrongIndex:      "ErrSSGenWrongIndex",
-	ErrSSGenWrongTxTree:     "ErrSSGenWrongTxTree",
-	ErrSSGenNoStakebase:     "ErrSSGenNoStakebase",
-	ErrSSGenNoReference:     "ErrSSGenNoReference",
-	ErrSSGenBadReference:    "ErrSSGenBadReference",
-	ErrSSGenNoVotePush:      "ErrSSGenNoVotePush",
-	ErrSSGenBadVotePush:     "ErrSSGenBadVotePush",
-	ErrSSGenBadGenOuts:      "ErrSSGenBadGenOuts",
-	ErrSSRtxWrongNumInputs:  "ErrSSRtxWrongNumInputs",
-	ErrSSRtxTooManyOutputs:  "ErrSSRtxTooManyOutputs",
-	ErrSSRtxNoOutputs:       "ErrSSRtxNoOutputs",
-	ErrSSRtxWrongTxTree:     "ErrSSRtxWrongTxTree",
-	ErrSSRtxBadOuts:         "ErrSSRtxBadOuts",
-	ErrVerSStxAmts:          "ErrVerSStxAmts",
-	ErrVerifyInput:          "ErrVerifyInput",
-	ErrVerifyOutType:        "ErrVerifyOutType",
-	ErrVerifyTooMuchFees:    "ErrVerifyTooMuchFees",
-	ErrVerifySpendTooMuch:   "ErrVerifySpendTooMuch",
-	ErrVerifyOutputAmt:      "ErrVerifyOutputAmt",
-	ErrVerifyOutPkhs:        "ErrVerifyOutPkhs",
-	ErrDatabaseCorrupt:      "ErrDatabaseCorrupt",
-	ErrMissingDatabaseTx:    "ErrMissingDatabaseTx",
-	ErrMemoryCorruption:     "ErrMemoryCorruption",
-	ErrFindTicketIdxs:       "ErrFindTicketIdxs",
-	ErrMissingTicket:        "ErrMissingTicket",
-	ErrDuplicateTicket:      "ErrDuplicateTicket",
-	ErrUnknownTicketSpent:   "ErrUnknownTicketSpent",
-}
-
-// 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.  It is used to indicate that
-// processing of a block or transaction failed due to one of the many validation
-// rules.  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 related to stake transactions. 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
 }
 
-// GetCode satisfies the error interface and prints human-readable errors.
-func (e RuleError) GetCode() ErrorCode {
-	return e.ErrorCode
+// Unwrap returns the underlying wrapped rule error.
+func (e RuleError) Unwrap() error {
+	return e.Err
 }
 
 // stakeRuleError creates a RuleError given a set of arguments.
-func stakeRuleError(c ErrorCode, desc string) RuleError {
-	return RuleError{ErrorCode: c, Description: desc}
+func stakeRuleError(kind ErrorKind, desc string) RuleError {
+	return RuleError{Err: kind, Description: desc}
 }