Extended logic eval error

data/transactions/logic/eval.go

@@ -3938,3 +3938,31 @@ func opTxSubmit(cx *EvalContext) {
 	})
 	cx.subtxn = nil
 }
+
+// PcDetails return PC and disassembled instructions at PC up to 2 opcodes back
+func (cx *EvalContext) PcDetails() (pc int, dis string) {
+	const maxNumAdditionalOpcodes = 2
+	text, ds, err := disassembleInstrumented(cx.program, nil)
+	if err != nil {
+		return cx.pc, dis
+	}
+
+	for i := 0; i < len(ds.pcOffset); i++ {
+		if ds.pcOffset[i].PC == cx.pc {
+			start := 0
+			if i >= maxNumAdditionalOpcodes {
+				start = i - maxNumAdditionalOpcodes
+			}
+
+			startTextPos := ds.pcOffset[start].Offset
+			endTextPos := len(text)
+			if i+1 < len(ds.pcOffset) {
+				endTextPos = ds.pcOffset[i+1].Offset
+			}
+
+			dis = text[startTextPos:endTextPos]
+			break
+		}
+	}
+	return cx.pc, dis
+}

data/transactions/logic/eval_test.go

@@ -4842,3 +4842,42 @@ func TestLog(t *testing.T) {
 		require.False(t, pass)
 	}
 }
+
+func TestPcDetails(t *testing.T) {
+	partitiontest.PartitionTest(t)
+	t.Parallel()
+
+	var tests = []struct {
+		source string
+		pc     int
+		det    string
+	}{
+		{"int 1; int 2; -", 5, "pushint 1\npushint 2\n-\n"},
+		{"int 1; err", 3, "pushint 1\nerr\n"},
+		{"int 1; dup; int 2; -; +", 6, "dup\npushint 2\n-\n"},
+		{"b end; end:", 4, ""},
+	}
+	for i, test := range tests {
+		t.Run(fmt.Sprintf("i=%d", i), func(t *testing.T) {
+			ops := testProg(t, test.source, LogicVersion)
+			txn := makeSampleTxn()
+			txgroup := makeSampleTxnGroup(txn)
+			txn.Lsig.Logic = ops.Program
+			sb := strings.Builder{}
+			ep := defaultEvalParams(&sb, &txn)
+			ep.TxnGroup = txgroup
+
+			var cx EvalContext
+			cx.EvalParams = ep
+			cx.runModeFlags = runModeSignature
+
+			pass, err := eval(ops.Program, &cx)
+			require.Error(t, err)
+			require.False(t, pass)
+
+			pc, det := cx.PcDetails()
+			require.Equal(t, test.pc, pc)
+			require.Equal(t, test.det, det)
+		})
+	}
+}

ledger/appcow.go

@@ -490,7 +490,12 @@ func (cb *roundCowState) StatefulEval(params logic.EvalParams, aidx basics.AppIn
 	var cx *logic.EvalContext
 	pass, cx, err = logic.EvalStatefulCx(program, params)
 	if err != nil {
-		return false, transactions.EvalDelta{}, ledgercore.LogicEvalError{Err: err}
+		var details string
+		if cx != nil {
+			pc, det := cx.PcDetails()
+			details = fmt.Sprintf("pc=%d, opcodes=%s", pc, det)
+		}
+		return false, transactions.EvalDelta{}, ledgercore.LogicEvalError{Err: err, Details: details}
 	}
 
 	// If program passed, build our eval delta, and commit to state changes

ledger/ledgercore/error.go

@@ -79,12 +79,17 @@ func (err ErrNoEntry) Error() string {
 
 // LogicEvalError indicates TEAL evaluation failure
 type LogicEvalError struct {
-	Err error
+	Err     error
+	Details string
 }
 
 // Error satisfies builtin interface `error`
 func (err LogicEvalError) Error() string {
-	return fmt.Sprintf("logic eval error: %v", err.Err)
+	msg := fmt.Sprintf("logic eval error: %v", err.Err)
+	if len(err.Details) > 0 {
+		msg = fmt.Sprintf("%s. Details: %s", msg, err.Details)
+	}
+	return msg
 }
 
 // ErrNonSequentialBlockEval provides feedback when the evaluator cannot be created for