Remove most panics

Remove most panics. The only ones remaining are in writeBuf when the
messages are too long (added in #1161). I think that's probably okay:
normal operations should never hit this.

Author: arp242

array.go

@@ -684,10 +684,10 @@ func (a StringArray) Value() (driver.Value, error) {
 	return "{}", nil
 }
 
-// appendArray appends rv to the buffer, returning the extended buffer and
-// the delimiter used between elements.
+// appendArray appends rv to the buffer, returning the extended buffer and the
+// delimiter used between elements.
 //
-// It panics when n <= 0 or rv's Kind is not reflect.Array nor reflect.Slice.
+// Returns an error when n <= 0 or rv is not a reflect.Array or reflect.Slice.
 func appendArray(b []byte, rv reflect.Value, n int) ([]byte, string, error) {
 	var del string
 	var err error
@@ -770,7 +770,11 @@ func appendArrayQuotedBytes(b, v []byte) []byte {
 }
 
 func appendValue(b []byte, v driver.Value) ([]byte, error) {
-	return append(b, encode(nil, v, 0)...), nil
+	enc, err := encode(nil, v, 0)
+	if err != nil {
+		return nil, err
+	}
+	return append(b, enc...), nil
 }
 
 // parseArray extracts the dimensions and elements of an array represented in

buf.go

@@ -3,6 +3,7 @@ package pq
 import (
 	"bytes"
 	"encoding/binary"
+	"fmt"
 	"math"
 
 	"github.com/lib/pq/internal/proto"
@@ -33,7 +34,7 @@ func (b *readBuf) int16() (n int) {
 func (b *readBuf) string() string {
 	i := bytes.IndexByte(*b, 0)
 	if i < 0 {
-		errorf("invalid message format; expected string terminator")
+		panic(fmt.Errorf("pq: invalid message format; expected string terminator"))
 	}
 	s := (*b)[:i]
 	*b = (*b)[i+1:]
@@ -82,7 +83,7 @@ func (b *writeBuf) bytes(v []byte) {
 func (b *writeBuf) wrap() []byte {
 	p := b.buf[b.pos:]
 	if len(p) > math.MaxUint32 {
-		errorf("message too large (%d > math.MaxUint32)", len(p))
+		panic(fmt.Errorf("pq: message too large (%d > math.MaxUint32)", len(p)))
 	}
 	binary.BigEndian.PutUint32(p, uint32(len(p)))
 	return b.buf
@@ -91,7 +92,7 @@ func (b *writeBuf) wrap() []byte {
 func (b *writeBuf) next(c proto.RequestCode) {
 	p := b.buf[b.pos:]
 	if len(p) > math.MaxUint32 {
-		errorf("message too large (%d > math.MaxUint32)", len(p))
+		panic(fmt.Errorf("pq: message too large (%d > math.MaxUint32)", len(p)))
 	}
 	binary.BigEndian.PutUint32(p, uint32(len(p)))
 	b.pos = len(b.buf) + 1