Add fromCharMap and fromStringMap

core/shared/src/main/scala/cats/parse/Parser.scala

@@ -981,6 +981,22 @@ object Parser {
     if (str.length == 0) unit
     else ignoreCase(str)
 
+  /** Convert a Map[Char, A] to Parser[A] first match a character, then map it to a value A
+    */
+  def fromCharMap[A](charMap: Map[Char, A]): Parser[A] =
+    charIn(charMap.keySet).map(charMap)
+
+  /** Convert a Map[String, A] to Parser[A] first match a character, then map it to a value A This
+    * throws if any of the keys are the empty string
+    */
+  def fromStringMap[A](stringMap: Map[String, A]): Parser[A] =
+    stringIn(stringMap.keySet).map(stringMap)
+
+  /** Convert a Map[String, A] to Parser[A] first match a character, then map it to a value A
+    */
+  def fromStringMap0[A](stringMap: Map[String, A]): Parser0[A] =
+    stringIn0(stringMap.keySet).map(stringMap)
+
   /** go through the list of parsers trying each as long as they are epsilon failures (don't
     * advance) see @backtrack if you want to do backtracking.
     *

core/shared/src/test/scala/cats/parse/ParserTest.scala

@@ -2513,6 +2513,31 @@ class ParserTest extends munit.ScalaCheckSuite {
     }
   }
 
+  property("fromCharMap works as expected") {
+    forAll { (cm: Map[Char, Int], str: String) =>
+      val p = Parser.fromCharMap(cm)
+
+      assertEquals(p.parseAll(str), Parser.charIn(cm.keySet).parseAll(str).map(cm(_)))
+    }
+  }
+
+  property("fromStringMap works as expected") {
+    forAll { (cm0: Map[String, Int], str: String) =>
+      val cm = cm0.filterNot(_._1.isEmpty)
+      val p = Parser.fromStringMap(cm)
+
+      assertEquals(p.parseAll(str), Parser.stringIn(cm.keySet).parseAll(str).map(cm(_)))
+    }
+  }
+
+  property("fromStringMap0 works as expected") {
+    forAll { (cm: Map[String, Int], str: String) =>
+      val p = Parser.fromStringMap0(cm)
+
+      assertEquals(p.parseAll(str), Parser.stringIn0(cm.keySet).parseAll(str).map(cm(_)))
+    }
+  }
+
   property("a context0 added is always at the top") {
     forAll(ParserGen.gen0, Arbitrary.arbitrary[List[String]], Arbitrary.arbitrary[String]) {
       (genP, ctx, str) =>