[Commonizer] Allow empty SharedCommonizerTarget

native/commonizer-api/src/org/jetbrains/kotlin/commonizer/CommonizerTarget.kt

@@ -34,10 +34,6 @@ public data class SharedCommonizerTarget(val targets: Set<CommonizerTarget>) : C
             return if (targets.isNotEmpty()) SharedCommonizerTarget(targets) else null
         }
     }
-
-    init {
-        require(targets.isNotEmpty()) { "Empty 'SharedCommonizerTarget': Expected at least one target" }
-    }
 }
 
 public fun CommonizerTarget(konanTargets: Iterable<KonanTarget>): CommonizerTarget {
@@ -101,6 +97,6 @@ public val CommonizerTarget.level: Int
     get() {
         return when (this) {
             is LeafCommonizerTarget -> return 0
-            is SharedCommonizerTarget -> targets.maxOf { it.level } + 1
+            is SharedCommonizerTarget -> if (targets.isNotEmpty()) targets.maxOf { it.level } + 1 else 0
         }
     }

native/commonizer-api/src/org/jetbrains/kotlin/commonizer/parseCommonizerTarget.kt

@@ -46,8 +46,8 @@ private sealed class IdentityStringToken {
         return when (this) {
             is Word -> value
             is Separator -> ", "
-            is SharedTargetStart -> "["
-            is SharedTargetEnd -> "]"
+            is SharedTargetStart -> "("
+            is SharedTargetEnd -> ")"
         }
     }
 }
@@ -118,11 +118,11 @@ private data class AnyOfParser<T : Any>(val parsers: List<Parser<T>>) : Parser<T
     }
 }
 
-private fun <T : Any> Parser<T>.oneOrMore(): Parser<List<T>> {
-    return OneOrMoreParser(this)
+private fun <T : Any> Parser<T>.zeroOrMore(): Parser<List<T>> {
+    return ZeroOrMoreParser(this)
 }
 
-private data class OneOrMoreParser<T : Any>(val parser: Parser<T>) : Parser<List<T>> {
+private data class ZeroOrMoreParser<T : Any>(val parser: Parser<T>) : Parser<List<T>> {
     override fun invoke(tokens: List<IdentityStringToken>): ParserOutput<List<T>>? {
         val outputs = mutableListOf<T>()
         var remainingTokens = tokens
@@ -132,9 +132,6 @@ private data class OneOrMoreParser<T : Any>(val parser: Parser<T>) : Parser<List
             outputs.add(output.value)
             remainingTokens = output.remaining
         }
-        if (outputs.isEmpty()) {
-            return null
-        }
         return ParserOutput(outputs.toList(), remainingTokens)
     }
 }
@@ -162,12 +159,12 @@ private object SharedTargetParser : Parser<SharedTargetSyntaxNode> {
     override fun invoke(tokens: List<IdentityStringToken>): ParserOutput<SharedTargetSyntaxNode>? {
         if (tokens.firstOrNull() !is SharedTargetStart) return null
 
-        val innerParser = anyOf(LeafTargetParser, SharedTargetParser).ignore(Separator).oneOrMore()
+        val innerParser = anyOf(LeafTargetParser, SharedTargetParser).ignore(Separator).zeroOrMore()
         val innerParserOutput = innerParser(tokens.drop(1)) ?: return null
 
         val closingToken = innerParserOutput.remaining.firstOrNull()
         if (closingToken != SharedTargetEnd) {
-            error("Missing ']' at ${tokens.joinToString("")}")
+            error("Missing '${SharedTargetEnd}' at ${tokens.joinToString("")}")
         }
 
         return ParserOutput(SharedTargetSyntaxNode(innerParserOutput.value), innerParserOutput.remaining.drop(1))

native/commonizer-api/test/org/jetbrains/kotlin/commonizer/CommonizerTargetIdentityStringTest.kt

@@ -85,6 +85,11 @@ class CommonizerTargetIdentityStringTest {
         )
     }
 
+    @Test
+    fun `empty shared target`() {
+        assertEquals(SharedCommonizerTarget(emptySet<CommonizerTarget>()), parseCommonizerTarget("()"))
+    }
+
     @Test(expected = IllegalArgumentException::class)
     fun `fail parsing CommonizerTarget 1`() {
         parseCommonizerTarget("xxx,")
@@ -95,11 +100,6 @@ class CommonizerTargetIdentityStringTest {
         parseCommonizerTarget("")
     }
 
-    @Test(expected = IllegalArgumentException::class)
-    fun `fail parsing CommonizerTarget 3`() {
-        parseCommonizerTarget("()")
-    }
-
     @Test(expected = IllegalArgumentException::class)
     fun `fail parsing CommonizerTarget 4`() {
         parseCommonizerTarget("(xxx")

native/commonizer-api/test/org/jetbrains/kotlin/commonizer/CommonizerTargetPrettyNameTest.kt

@@ -72,9 +72,11 @@ class CommonizerTargetPrettyNameTest {
         )
     }
 
-    @Test(expected = IllegalArgumentException::class)
+    @Test
     fun sharedTargetNoInnerTargets() {
-        SharedCommonizerTarget(emptySet<CommonizerTarget>())
+        assertEquals(
+            "[]", SharedCommonizerTarget(emptySet<CommonizerTarget>()).prettyName
+        )
     }
 
     private companion object {