Properly handle quoted 'null' literals in lenient mode (#1637)

Fixes #1600
Kotlin · Aug 17, 2021 · d00bff2 · d00bff2
1 parent 4755b24
commit d00bff2
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Showing 2 changed files with 26 additions and 8 deletions.
diff --git a/formats/json/commonMain/src/kotlinx/serialization/json/internal/JsonLexer.kt b/formats/json/commonMain/src/kotlinx/serialization/json/internal/JsonLexer.kt
@@ -368,13 +368,21 @@ internal class JsonLexer(private val source: String) {
 
     fun consumeStringLenientNotNull(): String {
         val result = consumeStringLenient()
-        if (result == NULL) { // Check if lenient value is 'null' and fail for non-nullable read if so
+        /*
+         * Check if lenient value is 'null' _without_ quotation marks and fail for non-nullable read if so.
+         */
+        if (result == NULL && wasUnquotedString()) {
             fail("Unexpected 'null' value instead of string literal")
         }
         return result
     }
 
-    // Allows to consume unquoted string
+    private fun wasUnquotedString(): Boolean {
+        // Is invoked _only_ when the 'null' string was read, thus 'cP - 1' is always within bounds
+        return source[currentPosition - 1] != STRING
+    }
+
+    // Allows consuming unquoted string
     fun consumeStringLenient(): String {
         if (peekedString != null) {
             return takePeeked()

diff --git a/formats/json/commonTest/src/kotlinx/serialization/json/LenientTest.kt b/formats/json/commonTest/src/kotlinx/serialization/json/LenientTest.kt
@@ -4,12 +4,10 @@
 
 package kotlinx.serialization.json
 
-import kotlinx.serialization.Serializable
-import kotlinx.serialization.json.internal.JsonDecodingException
-import kotlinx.serialization.json.internal.JsonException
-import kotlin.test.Test
-import kotlin.test.assertEquals
-import kotlin.test.assertFailsWith
+import kotlinx.serialization.*
+import kotlinx.serialization.builtins.*
+import kotlinx.serialization.json.internal.*
+import kotlin.test.*
 
 class LenientTest : JsonTestBase() {
 
@@ -81,5 +79,17 @@ class LenientTest : JsonTestBase() {
         assertEquals(NullableString("nul"), lenient.decodeFromString("""{"s":nul}""", it))
         assertEquals(NullableString("null1"), lenient.decodeFromString("""{"s":null1}""", it))
         assertEquals(NullableString(null), lenient.decodeFromString("""{"s":null}""", it))
+        assertEquals(NullableString("null"), lenient.decodeFromString("""{"s":"null"}""", it))
+        assertEquals(NullableString("null"), lenient.decodeFromString("""{"s":"null"     }""", it))
+        assertEquals(NullableString("null  "), lenient.decodeFromString("""{"s":"null  "     }""", it))
+    }
+
+    @Test
+    fun testTopLevelNulls() = parametrizedTest {
+        assertEquals("nul", lenient.decodeFromString("""nul""", it))
+        assertEquals("null1", lenient.decodeFromString("""null1""", it))
+        assertEquals(null, lenient.decodeFromString(String.serializer().nullable, """null""", it))
+        assertEquals("null", lenient.decodeFromString(""""null"""", it))
+        assertEquals("null   ", lenient.decodeFromString(""""null   """", it))
     }
 }