Better error messages (#41)

builq.go

@@ -140,17 +140,17 @@ var (
 	// errUnsupportedVerb when %X is found and X isn't supported.
 	errUnsupportedVerb = errors.New("unsupported verb")
 
-	// errLonelyVerb when % is found without a verb.
-	errLonelyVerb = errors.New("lonely verb")
+	// errLonelyModifier when % is found without a verb.
+	errLonelyModifier = errors.New("lonely modifier without a verb")
 
 	// errIncorrectVerb is passed like `%+`.
 	errIncorrectVerb = errors.New("incorrect verb")
 
 	// errMixedPlaceholders when $ AND ? are mixed in 1 query.
-	errMixedPlaceholders = errors.New("mixed placeholders must not be used in a single query")
+	errMixedPlaceholders = errors.New("mixed placeholders in a single query")
 
 	// errNonSliceArgument when a non-slice argument passed to placeholder with `+` or `#`.
-	errNonSliceArgument = errors.New("non-slice arguments must not be used with slice modifiers")
+	errNonSliceArgument = errors.New("non-slice arguments with slice modifiers")
 
 	// errNonNumericArg expected number for %d but got something else.
 	errNonNumericArg = errors.New("expected numeric argument")

builq_test.go

@@ -38,17 +38,18 @@ func TestBuilder(t *testing.T) {
 		})
 	}
 
-	test("bad verb", errUnsupportedVerb, "SELECT * FROM %+ slice", 1)
-	test("bad verb", errUnsupportedVerb, "SELECT * FROM %+ slice", 1)
+	test("incorrect verb", errIncorrectVerb, "SELECT * FROM %+ slice", 1)
+	test("incorrect verb", errIncorrectVerb, "SELECT * FROM %+ slice", 1)
 	test("incorrect verb 1", errIncorrectVerb, "SELECT * FROM %+", 1)
 	test("incorrect verb 2", errIncorrectVerb, "SELECT * FROM %#", 1)
-	test("lonely verb", errLonelyVerb, "SELECT * FROM % super")
-	test("lonely verb", errLonelyVerb, "SELECT foo FROM bar%")
+	test("lonely verb", errLonelyModifier, "SELECT * FROM % super")
+	test("lonely verb", errLonelyModifier, "SELECT foo FROM bar%")
 	test("too few arguments", errTooFewArguments, "SELECT foo FROM bar%d")
 	test("too few arguments", errTooFewArguments, "SELECT * FROM %s")
 	test("too few arguments", errTooFewArguments, "SELECT * FROM %$")
 	test("too few arguments", errTooFewArguments, "SELECT * FROM %+?")
 	test("too many arguments", errTooManyArguments, "SELECT * FROM %s", "users", "users")
+	test("unsupported verb", errUnsupportedVerb, "SELECT * FROM %+x")
 	test("unsupported verb", errUnsupportedVerb, "SELECT * FROM %v", "users")
 	test("mixed placeholders", errMixedPlaceholders, "WHERE foo = %$ AND bar = %?", 1, 2)
 	test("non-slice argument", errNonSliceArgument, "WHERE foo = %+$", 1)
@@ -79,7 +80,7 @@ func FuzzBuilder(f *testing.F) {
 			if errors.Is(err, errTooFewArguments) ||
 				errors.Is(err, errTooManyArguments) ||
 				errors.Is(err, errUnsupportedVerb) ||
-				errors.Is(err, errLonelyVerb) ||
+				errors.Is(err, errLonelyModifier) ||
 				errors.Is(err, errIncorrectVerb) ||
 				errors.Is(err, errMixedPlaceholders) ||
 				errors.Is(err, errNonSliceArgument) ||

write.go

@@ -12,26 +12,27 @@ func (b *Builder) write(sb *strings.Builder, resArgs *[]any, s string, args ...a
 	for argID := 0; ; argID++ {
 		idx := strings.IndexByte(s, '%')
 		if idx == -1 {
-			if argID != len(args) {
-				b.setErr(errTooManyArguments)
+			var err error
+			if len(args) != argID {
+				err = fmt.Errorf("%w: have %d args, expected %d", errTooManyArguments, len(args), argID)
 			}
 
 			sb.WriteString(s)
 			sb.WriteByte(b.sep)
-			return nil
+			return err
 		}
 
 		sb.WriteString(s[:idx])
 
 		s = s[idx+1:] // skip '%'
 		if len(s) == 0 {
-			return errLonelyVerb
+			return errLonelyModifier
 		}
 
 		switch verb := s[0]; verb {
 		case '$', '?', 's', 'd':
 			if argID >= len(args) {
-				return errTooFewArguments
+				return fmt.Errorf("%w: have %d args, want %d", errTooFewArguments, len(args), argID+1)
 			}
 
 			arg := args[argID]
@@ -41,15 +42,14 @@ func (b *Builder) write(sb *strings.Builder, resArgs *[]any, s string, args ...a
 		case '+', '#':
 			isBatch := verb == '#'
 			s = s[1:]
-			if len(s) < 1 {
-				b.setErr(errIncorrectVerb)
-				continue
+			if len(s) < 1 || s[0] == ' ' {
+				return fmt.Errorf("%w: '%c' requires additional '$' or '?'", errIncorrectVerb, verb)
 			}
 
 			switch verb := s[0]; verb {
 			case '$', '?':
 				if argID >= len(args) {
-					return errTooFewArguments
+					return fmt.Errorf("%w: have %d args, want %d", errTooFewArguments, len(args), argID+1)
 				}
 
 				arg := args[argID]
@@ -60,8 +60,9 @@ func (b *Builder) write(sb *strings.Builder, resArgs *[]any, s string, args ...a
 				} else {
 					b.writeSlice(sb, resArgs, verb, arg)
 				}
+
 			default:
-				b.setErr(errUnsupportedVerb)
+				return fmt.Errorf("%w: '%c' is not supported", errUnsupportedVerb, verb)
 			}
 
 		case '%':
@@ -70,10 +71,10 @@ func (b *Builder) write(sb *strings.Builder, resArgs *[]any, s string, args ...a
 			sb.WriteByte('%')
 
 		case ' ':
-			b.setErr(errLonelyVerb)
+			return errLonelyModifier
 
 		default:
-			b.setErr(errUnsupportedVerb)
+			return fmt.Errorf("%w: '%c' is not supported", errUnsupportedVerb, verb)
 		}
 	}
 }
@@ -136,12 +137,10 @@ func (b *Builder) writeArg(sb *strings.Builder, resArgs *[]any, verb byte, arg a
 		return
 	}
 
-	// store the first placeholder used in the query
-	// to check for mixed placeholders later
-	if b.placeholder == 0 {
+	switch {
+	case b.placeholder == 0:
 		b.placeholder = verb
-	}
-	if b.placeholder != verb {
+	case b.placeholder != verb:
 		b.setErr(errMixedPlaceholders)
 	}
 }
@@ -188,12 +187,6 @@ func (b *Builder) asSlice(v any) []any {
 	return res
 }
 
-func (b *Builder) setErr(err error) {
-	if b.err == nil {
-		b.err = err
-	}
-}
-
 func (b *Builder) assertNumber(v any) {
 	switch v.(type) {
 	case int, int8, int16, int32, int64,
@@ -203,3 +196,9 @@ func (b *Builder) assertNumber(v any) {
 		b.setErr(errNonNumericArg)
 	}
 }
+
+func (b *Builder) setErr(err error) {
+	if b.err == nil {
+		b.err = err
+	}
+}