parser: fix parse on ${A}

Fix a parse bug on ${A}

Fixes: #I1T68Q
Signed-off-by: Njingxiaolu <lujingxiao@huawei.com>

builder/dockerfile/parser/util.go

@@ -23,7 +23,7 @@ import (
 var (
 	// Split ${param} or $param.
 	// param should start with char
-	regParam = regexp.MustCompile(`[a-zA-Z][a-zA-Z0-9\-_]+`)
+	regParam = regexp.MustCompile(`^[a-zA-Z][a-zA-Z0-9\-_]*`)
 	// regParamSpecial use to match ${variable:-word} and ${variable:+word}
 	regParamSpecial = regexp.MustCompile(`[a-zA-Z][a-zA-Z0-9\-\+_:]+`)
 )

builder/dockerfile/parser/util_test.go

@@ -73,6 +73,11 @@ func TestRegParam(t *testing.T) {
 			param:     "1212",
 			matchFull: false,
 		},
+		{
+			name:      "name 16",
+			param:     "A",
+			matchFull: true,
+		},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
@@ -356,6 +361,22 @@ func TestResolveParam(t *testing.T) {
 			want:    `\$`,
 			wantErr: false,
 		},
+		{
+			name: "case 107",
+			args: args{
+				s:      `${A}`,
+				strict: false,
+				resolveArg: func(s string) string {
+					if s == "A" {
+						return "found"
+					} else {
+						return "fail"
+					}
+				},
+			},
+			want:    `found`,
+			wantErr: false,
+		},
 		{
 			// ${variable:-name}, match variable, return $variable
 			name: "case 201",