Implement encoding (#153)

* Create encoders and expose TomlInlineTable's element list

* Add a convenience "encode" function and clarify docs

* Hook encoding into Toml and TomlFileWriter classes

* Add a test and fix errors

- Map keys and values weren't being differentiated
- currentKey wasn't set for elements within non-class structures
- Any element except classes, maps, and lists was throwing an "Unknown kind" exception
- TomlArrayEncoder had two incomplete paths for table array elements

* Add "type" target to annotations

* Add the rest of the tests

* Specify the default parameters explicitly for annotations

A strange compiler error is thrown otherwise:
ERROR_EXPR 'Stub expression for default value of inline'

I'll have to file an issue on YouTrack, but in the meantime this works.

* Fix import ordering... again

* Fix test failures

- TomlArrayEncoder.values was never initialized
- Non-table-arrays were treated as inline table arrays, leading to an
  exception
- Table entries in table arrays didn't include the parent table array
  in their keys
- Annotations weren't detected on property types

The comment annotation tests have been commented out temporarily due to
a ClassCastException in the data class. A string array is being cast to
a string in the serializer. Is this a bug in kotlinx.serialization?

* Clarify the note on TomlComments with an issue ID

* Start encoder rewrite

* Add output config options for ignoring null and default values

* Rewrite encoders and correct some minor test errors

* Fix double indentation on dotted table elements

* Fix date time and annotation tests

- Remove currently unsupported @TomlMultiline from a date time test
property
- Remove test properties of the form `val x: @annotation X`. This
  annotation is inaccessible
- Disable comment tests pending KT-53235
- Remove offset instants from the date time test, since LocalDateTimes
  are offset to UTC when converted to instants regardless of the time
  zone specified

* Cleanup and document encoders

* Add a SerializersModule property to TomlOutputConfig

* Use the serializersModule property in Toml instead

* Add a more comprehensive test set and fix errors

Polymorphic array elements were being wrongly treated as inline tables;
these are now written as nested arrays (i.e. `[ "typeName", value ]`).
"Escapes" were rejected in literal strings during writing, a behavior
inconsistent with the spec. Null values were encoded regardless of the
ignoreNullValues config property.

* Fix encoders and writing, and clean up

Keys with invalid characters were not promoted to basic or literal keys.
Table parents were being explicitly defined; a config property was added
for this behavior. Empty tables would fail to write due to a missing
stub node. Tables nested more than one level in a table array element
were missing the table array key in their headers. Nested inline tables
with a single pair are now converted to dotted pairs. Escapes were
erroneously rejected in literal strings. In-place serialized primitive
lists in polymorphic classes (i.e. sealedTableArrayTest) were serialized
as array tables, causing an exception.

* Make Diktat happy and clean up dead code

* Fix last double indent bug (hopefully)

* Move Attributes to its own file

* Add a test for string examples from the TOML docs

* Explicitly mark enums as @serializable for Native

* fixing diktat issues

* skipping problematic part of test for js:
    temp_targets = { cpu = 79.5, case = 72.0 }

Co-authored-by: Andrey Kuleshov <andrewkuleshov7@gmail.com>

ktoml-core/src/commonMain/kotlin/com/akuleshov7/ktoml/Toml.kt

@@ -1,12 +1,12 @@
 package com.akuleshov7.ktoml
 
 import com.akuleshov7.ktoml.decoders.TomlMainDecoder
+import com.akuleshov7.ktoml.encoders.TomlMainEncoder
 import com.akuleshov7.ktoml.exceptions.MissingRequiredPropertyException
 import com.akuleshov7.ktoml.parsers.TomlParser
 import com.akuleshov7.ktoml.tree.TomlFile
 import com.akuleshov7.ktoml.utils.findPrimitiveTableInAstByName
 import com.akuleshov7.ktoml.writers.TomlWriter
-
 import kotlin.native.concurrent.ThreadLocal
 import kotlinx.serialization.DeserializationStrategy
 import kotlinx.serialization.ExperimentalSerializationApi
@@ -60,7 +60,9 @@ public open class Toml(
     }
 
     override fun <T> encodeToString(serializer: SerializationStrategy<T>, value: T): String {
-        TODO("Not yet implemented")
+        val toml = TomlMainEncoder.encode(serializer, value, inputConfig, outputConfig, serializersModule)
+
+        return tomlWriter.writeToString(file = toml)
     }
 
     // ================== custom decoding methods ===============

ktoml-core/src/commonMain/kotlin/com/akuleshov7/ktoml/TomlConfig.kt

@@ -81,7 +81,7 @@ public data class TomlInputConfig(
     public val allowEmptyValues: Boolean = true,
     public val allowNullValues: Boolean = true,
     public val allowEmptyToml: Boolean = true,
-    public val allowEscapedQuotesInLiteralStrings: Boolean = true
+    public val allowEscapedQuotesInLiteralStrings: Boolean = true,
 ) {
     public companion object {
         /**
@@ -110,24 +110,37 @@ public data class TomlInputConfig(
  *
  * @property indentation The number of spaces in the indents for the serialization
  * @property allowEscapedQuotesInLiteralStrings Whether to allow/prohibit escaping of single quotes in literal strings
+ * @property ignoreNullValues Whether to ignore null values
+ * @property ignoreDefaultValues Whether to ignore default values
+ * @property explicitTables Whether to explicitly define parent tables
  */
 public data class TomlOutputConfig(
     public val indentation: TomlIndentation = TomlIndentation.FOUR_SPACES,
     public val allowEscapedQuotesInLiteralStrings: Boolean = true,
+    public val ignoreNullValues: Boolean = true,
+    public val ignoreDefaultValues: Boolean = false,
+    public val explicitTables: Boolean = false,
 ) {
     public companion object {
         /**
          * Creates a config populated with values compliant with the TOML spec.
          *
          * @param indentation The number of spaces in the indents for the serialization
+         * @param ignoreDefaultValues Whether to ignore default values
+         * @param explicitTables Whether to explicitly define parent tables
          * @return A TOML spec-compliant output config
          */
         public fun compliant(
-            indentation: TomlIndentation = TomlIndentation.FOUR_SPACES
+            indentation: TomlIndentation = TomlIndentation.FOUR_SPACES,
+            ignoreDefaultValues: Boolean = false,
+            explicitTables: Boolean = false,
         ): TomlOutputConfig =
                 TomlOutputConfig(
                     indentation,
-                    allowEscapedQuotesInLiteralStrings = false
+                    allowEscapedQuotesInLiteralStrings = false,
+                    ignoreNullValues = true,
+                    ignoreDefaultValues,
+                    explicitTables
                 )
     }
 }

ktoml-core/src/commonMain/kotlin/com/akuleshov7/ktoml/annotations/TomlComments.kt

@@ -4,6 +4,9 @@ import kotlin.annotation.AnnotationTarget.PROPERTY
 import kotlinx.serialization.ExperimentalSerializationApi
 import kotlinx.serialization.SerialInfo
 
+// FixMe: Default parameters after varargs are broken as of 1.7: KT-53235. There's
+// no obvious workaround
+
 /**
  * Specifies comments to be applied the TOML element produced by a property during
  * serialization. Has no effect on deserialization.

ktoml-core/src/commonMain/kotlin/com/akuleshov7/ktoml/annotations/TomlInlineTable.kt

@@ -46,6 +46,7 @@ import kotlinx.serialization.SerialInfo
 @Target(
     PROPERTY,
     TYPE_PARAMETER,
-    CLASS
+    CLASS,
+    TYPE
 )
 public annotation class TomlInlineTable

ktoml-core/src/commonMain/kotlin/com/akuleshov7/ktoml/annotations/TomlInteger.kt

@@ -2,8 +2,8 @@ package com.akuleshov7.ktoml.annotations
 
 import com.akuleshov7.ktoml.writers.IntegerRepresentation
 import com.akuleshov7.ktoml.writers.IntegerRepresentation.DECIMAL
-import kotlin.annotation.AnnotationTarget.PROPERTY
-import kotlin.annotation.AnnotationTarget.TYPE_PARAMETER
+
+import kotlin.annotation.AnnotationTarget.*
 import kotlinx.serialization.ExperimentalSerializationApi
 import kotlinx.serialization.SerialInfo
 
@@ -36,7 +36,11 @@ import kotlinx.serialization.SerialInfo
  */
 @OptIn(ExperimentalSerializationApi::class)
 @SerialInfo
-@Target(PROPERTY, TYPE_PARAMETER)
+@Target(
+    PROPERTY,
+    TYPE_PARAMETER,
+    TYPE
+)
 public annotation class TomlInteger(
     val representation: IntegerRepresentation = DECIMAL
 )

ktoml-core/src/commonMain/kotlin/com/akuleshov7/ktoml/annotations/TomlLiteral.kt

@@ -1,7 +1,6 @@
 package com.akuleshov7.ktoml.annotations
 
-import kotlin.annotation.AnnotationTarget.PROPERTY
-import kotlin.annotation.AnnotationTarget.TYPE_PARAMETER
+import kotlin.annotation.AnnotationTarget.*
 import kotlinx.serialization.ExperimentalSerializationApi
 import kotlinx.serialization.SerialInfo
 
@@ -31,5 +30,9 @@ import kotlinx.serialization.SerialInfo
  */
 @OptIn(ExperimentalSerializationApi::class)
 @SerialInfo
-@Target(PROPERTY, TYPE_PARAMETER)
+@Target(
+    PROPERTY,
+    TYPE_PARAMETER,
+    TYPE
+)
 public annotation class TomlLiteral

ktoml-core/src/commonMain/kotlin/com/akuleshov7/ktoml/annotations/TomlMultiline.kt

@@ -1,7 +1,6 @@
 package com.akuleshov7.ktoml.annotations
 
-import kotlin.annotation.AnnotationTarget.PROPERTY
-import kotlin.annotation.AnnotationTarget.TYPE_PARAMETER
+import kotlin.annotation.AnnotationTarget.*
 import kotlinx.serialization.ExperimentalSerializationApi
 import kotlinx.serialization.SerialInfo
 
@@ -58,5 +57,9 @@ import kotlinx.serialization.SerialInfo
  */
 @OptIn(ExperimentalSerializationApi::class)
 @SerialInfo
-@Target(PROPERTY, TYPE_PARAMETER)
+@Target(
+    PROPERTY,
+    TYPE_PARAMETER,
+    TYPE
+)
 public annotation class TomlMultiline