Script that can read and parse Unity YAML files into basic trees.

UYAMLObjects.cs

using Lachee.Utilities.Serialization;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Lachee.Utilities.Serialization
{
    public interface IUPropertyCollection
    {
        bool Add(UProperty property);
    }

    /// <summary>Basic data structure</summary>
    public class UNode { }
    /// <summary>Stores a key pair</summary>
    public class UProperty
    {
        public string name;
        public UNode value;
    }
    /// <summary>Stores a single value</summary>
    public class UValue : UNode
    {
        public string value = "";
        public UValue() { }
        public UValue(string value)
        {
            this.value = value;
        }

        public override string ToString()
            => value;
    }
    /// <summary>Stores an array of values/objects</summary>
    public class UArray : UNode, IUPropertyCollection
    {
        public List<UNode> items = new List<UNode>();

        public bool Add(UProperty property)
            => Add(property.value);

        public bool Add(UNode node)
        {
            items.Add(node);
            return true;
        }
    }
    /// <summary>Stores a map of names and properties</summary>
    public class UObject : UNode, IUPropertyCollection
    {
        public Dictionary<string, UProperty> properties = new Dictionary<string, UProperty>();

        public bool Add(UProperty property)
            => properties.TryAdd(property.name, property);
    }
    /// <summary>A single asset/class</summary>
    public sealed class UComponent : UNode, IUPropertyCollection
    {
        public long fileID = -1;
        public UClassID classID = UClassID.Object;

        public string TypeName => _property?.name;
        public UObject Component => (UObject)_property?.value;
        public UProperty Property => _property;
        private UProperty _property;

        public bool Add(UProperty property)
        {
            if (!string.IsNullOrEmpty(TypeName))
                return false;

            _property = property;
            return true;
        }

        public override string ToString()
            => $"{classID} &{fileID}";
    }

    public enum UClassID
    {
        Object = 0,
        GameObject = 1,
        Component = 2,
        LevelGameManager = 3,
        Transform = 4,
        TimeManager = 5,
        GlobalGameManager = 6,
        Behaviour = 8,
        GameManager = 9,
        AudioManager = 11,
        InputManager = 13,
        EditorExtension = 18,
        Physics2DSettings = 19,
        Camera = 20,
        Material = 21,
        MeshRenderer = 23,
        Renderer = 25,
        Texture = 27,
        Texture2D = 28,
        OcclusionCullingSettings = 29,
        GraphicsSettings = 30,
        MeshFilter = 33,
        OcclusionPortal = 41,
        Mesh = 43,
        Skybox = 45,
        QualitySettings = 47,
        Shader = 48,
        TextAsset = 49,
        Rigidbody2D = 50,
        Collider2D = 53,
        Rigidbody = 54,
        PhysicsManager = 55,
        Collider = 56,
        Joint = 57,
        CircleCollider2D = 58,
        HingeJoint = 59,
        PolygonCollider2D = 60,
        BoxCollider2D = 61,
        PhysicsMaterial2D = 62,
        MeshCollider = 64,
        BoxCollider = 65,
        CompositeCollider2D = 66,
        EdgeCollider2D = 68,
        CapsuleCollider2D = 70,
        ComputeShader = 72,
        AnimationClip = 74,
        ConstantForce = 75,
        TagManager = 78,
        AudioListener = 81,
        AudioSource = 82,
        AudioClip = 83,
        RenderTexture = 84,
        CustomRenderTexture = 86,
        Cubemap = 89,
        Avatar = 90,
        AnimatorController = 91,
        RuntimeAnimatorController = 93,
        ScriptMapper = 94,
        Animator = 95,
        TrailRenderer = 96,
        DelayedCallManager = 98,
        TextMesh = 102,
        RenderSettings = 104,
        Light = 108,
        CGProgram = 109,
        BaseAnimationTrack = 110,
        Animation = 111,
        MonoBehaviour = 114,
        MonoScript = 115,
        MonoManager = 116,
        Texture3D = 117,
        NewAnimationTrack = 118,
        Projector = 119,
        LineRenderer = 120,
        Flare = 121,
        Halo = 122,
        LensFlare = 123,
        FlareLayer = 124,
        HaloLayer = 125,
        NavMeshProjectSettings = 126,
        Font = 128,
        PlayerSettings = 129,
        NamedObject = 130,
        PhysicMaterial = 134,
        SphereCollider = 135,
        CapsuleCollider = 136,
        SkinnedMeshRenderer = 137,
        FixedJoint = 138,
        BuildSettings = 141,
        AssetBundle = 142,
        CharacterController = 143,
        CharacterJoint = 144,
        SpringJoint = 145,
        WheelCollider = 146,
        ResourceManager = 147,
        PreloadData = 150,
        ConfigurableJoint = 153,
        TerrainCollider = 154,
        TerrainData = 156,
        LightmapSettings = 157,
        WebCamTexture = 158,
        EditorSettings = 159,
        EditorUserSettings = 162,
        AudioReverbFilter = 164,
        AudioHighPassFilter = 165,
        AudioChorusFilter = 166,
        AudioReverbZone = 167,
        AudioEchoFilter = 168,
        AudioLowPassFilter = 169,
        AudioDistortionFilter = 170,
        SparseTexture = 171,
        AudioBehaviour = 180,
        AudioFilter = 181,
        WindZone = 182,
        Cloth = 183,
        SubstanceArchive = 184,
        ProceduralMaterial = 185,
        ProceduralTexture = 186,
        Texture2DArray = 187,
        CubemapArray = 188,
        OffMeshLink = 191,
        OcclusionArea = 192,
        Tree = 193,
        NavMeshAgent = 195,
        NavMeshSettings = 196,
        ParticleSystem = 198,
        ParticleSystemRenderer = 199,
        ShaderVariantCollection = 200,
        LODGroup = 205,
        BlendTree = 206,
        Motion = 207,
        NavMeshObstacle = 208,
        SortingGroup = 210,
        SpriteRenderer = 212,
        Sprite = 213,
        CachedSpriteAtlas = 214,
        ReflectionProbe = 215,
        Terrain = 218,
        LightProbeGroup = 220,
        AnimatorOverrideController = 221,
        CanvasRenderer = 222,
        Canvas = 223,
        RectTransform = 224,
        CanvasGroup = 225,
        BillboardAsset = 226,
        BillboardRenderer = 227,
        SpeedTreeWindAsset = 228,
        AnchoredJoint2D = 229,
        Joint2D = 230,
        SpringJoint2D = 231,
        DistanceJoint2D = 232,
        HingeJoint2D = 233,
        SliderJoint2D = 234,
        WheelJoint2D = 235,
        ClusterInputManager = 236,
        BaseVideoTexture = 237,
        NavMeshData = 238,
        AudioMixer = 240,
        AudioMixerController = 241,
        AudioMixerGroupController = 243,
        AudioMixerEffectController = 244,
        AudioMixerSnapshotController = 245,
        PhysicsUpdateBehaviour2D = 246,
        ConstantForce2D = 247,
        Effector2D = 248,
        AreaEffector2D = 249,
        PointEffector2D = 250,
        PlatformEffector2D = 251,
        SurfaceEffector2D = 252,
        BuoyancyEffector2D = 253,
        RelativeJoint2D = 254,
        FixedJoint2D = 255,
        FrictionJoint2D = 256,
        TargetJoint2D = 257,
        LightProbes = 258,
        LightProbeProxyVolume = 259,
        SampleClip = 271,
        AudioMixerSnapshot = 272,
        AudioMixerGroup = 273,
        AssetBundleManifest = 290,
        RuntimeInitializeOnLoadManager = 300,
        UnityConnectSettings = 310,
        AvatarMask = 319,
        PlayableDirector = 320,
        VideoPlayer = 328,
        VideoClip = 329,
        ParticleSystemForceField = 330,
        SpriteMask = 331,
        WorldAnchor = 362,
        OcclusionCullingData = 363,
        PrefabInstance = 1001,
        EditorExtensionImpl = 1002,
        AssetImporter = 1003,
        AssetDatabaseV1 = 1004,
        Mesh3DSImporter = 1005,
        TextureImporter = 1006,
        ShaderImporter = 1007,
        ComputeShaderImporter = 1008,
        AudioImporter = 1020,
        HierarchyState = 1026,
        AssetMetaData = 1028,
        DefaultAsset = 1029,
        DefaultImporter = 1030,
        TextScriptImporter = 1031,
        SceneAsset = 1032,
        NativeFormatImporter = 1034,
        MonoImporter = 1035,
        LibraryAssetImporter = 1038,
        ModelImporter = 1040,
        FBXImporter = 1041,
        TrueTypeFontImporter = 1042,
        EditorBuildSettings = 1045,
        InspectorExpandedState = 1048,
        AnnotationManager = 1049,
        PluginImporter = 1050,
        EditorUserBuildSettings = 1051,
        IHVImageFormatImporter = 1055,
        AnimatorStateTransition = 1101,
        AnimatorState = 1102,
        HumanTemplate = 1105,
        AnimatorStateMachine = 1107,
        PreviewAnimationClip = 1108,
        AnimatorTransition = 1109,
        SpeedTreeImporter = 1110,
        AnimatorTransitionBase = 1111,
        SubstanceImporter = 1112,
        LightmapParameters = 1113,
        LightingDataAsset = 1120,
        SketchUpImporter = 1124,
        BuildReport = 1125,
        PackedAssets = 1126,
        VideoClipImporter = 1127,
        Int = 100000,
        Bool = 100001,
        Float = 100002,
        MonoObject = 100003,
        Collision = 100004,
        Vector3f = 100005,
        RootMotionData = 100006,
        Collision2D = 100007,
        AudioMixerLiveUpdateFloat = 100008,
        AudioMixerLiveUpdateBool = 100009,
        Polygon2D = 100010,
        Void = 100011,
        TilemapCollider2D = 19719996,
        AssetImporterLog = 41386430,
        VFXRenderer = 73398921,
        SerializableManagedRefTestClass = 76251197,
        Grid = 156049354,
        ScenesUsingAssets = 156483287,
        ArticulationBody = 171741748,
        Preset = 181963792,
        EmptyObject = 277625683,
        IConstraint = 285090594,
        TestObjectWithSpecialLayoutOne = 293259124,
        AssemblyDefinitionReferenceImporter = 294290339,
        SiblingDerived = 334799969,
        TestObjectWithSerializedMapStringNonAlignedStruct = 342846651,
        SubDerived = 367388927,
        AssetImportInProgressProxy = 369655926,
        PluginBuildInfo = 382020655,
        EditorProjectAccess = 426301858,
        PrefabImporter = 468431735,
        TestObjectWithSerializedArray = 478637458,
        TestObjectWithSerializedAnimationCurve = 478637459,
        TilemapRenderer = 483693784,
        ScriptableCamera = 488575907,
        SpriteAtlasAsset = 612988286,
        SpriteAtlasDatabase = 638013454,
        AudioBuildInfo = 641289076,
        CachedSpriteAtlasRuntimeData = 644342135,
        RendererFake = 646504946,
        AssemblyDefinitionReferenceAsset = 662584278,
        BuiltAssetBundleInfoSet = 668709126,
        SpriteAtlas = 687078895,
        RayTracingShaderImporter = 747330370,
        RayTracingShader = 825902497,
        LightingSettings = 850595691,
        PlatformModuleSetup = 877146078,
        VersionControlSettings = 890905787,
        AimConstraint = 895512359,
        VFXManager = 937362698,
        VisualEffectSubgraph = 994735392,
        VisualEffectSubgraphOperator = 994735403,
        VisualEffectSubgraphBlock = 994735404,
        Prefab = 1001480554,
        LocalizationImporter = 1027052791,
        Derived = 1091556383,
        PropertyModificationsTargetTestObject = 1111377672,
        ReferencesArtifactGenerator = 1114811875,
        AssemblyDefinitionAsset = 1152215463,
        SceneVisibilityState = 1154873562,
        LookAtConstraint = 1183024399,
        SpriteAtlasImporter = 1210832254,
        MultiArtifactTestImporter = 1223240404,
        GameObjectRecorder = 1268269756,
        LightingDataAssetParent = 1325145578,
        PresetManager = 1386491679,
        TestObjectWithSpecialLayoutTwo = 1392443030,
        StreamingManager = 1403656975,
        LowerResBlitTexture = 1480428607,
        StreamingController = 1542919678,
        TestObjectVectorPairStringBool = 1628831178,
        GridLayout = 1742807556,
        AssemblyDefinitionImporter = 1766753193,
        ParentConstraint = 1773428102,
        FakeComponent = 1803986026,
        PositionConstraint = 1818360608,
        RotationConstraint = 1818360609,
        ScaleConstraint = 1818360610,
        Tilemap = 1839735485,
        PackageManifest = 1896753125,
        PackageManifestImporter = 1896753126,
        TerrainLayer = 1953259897,
        SpriteShapeRenderer = 1971053207,
        NativeObjectType = 1977754360,
        TestObjectWithSerializedMapStringBool = 1981279845,
        SerializableManagedHost = 1995898324,
        VisualEffectAsset = 2058629509,
        VisualEffectImporter = 2058629510,
        VisualEffectResource = 2058629511,
        VisualEffectObject = 2059678085,
        VisualEffect = 2083052967,
        LocalizationAsset = 2083778819,
        ScriptedImporter = 2089858483,
    }
}

UYAMLParser.cs

using System.Text;
using System.Collections;
using System.Collections.Generic;
using System.ComponentModel;

namespace Lachee.Utilities.Serialization
{
    /// <summary>
    /// Simple Parser for Unity YAML files. Able to produce basic tree structures, it is suitable for raw manipulation of the data but not serialization.
    /// </summary>
    public sealed class UYAMLParser
    {
        internal const string COMPONENT_HEADER = "--- !u!";

        private IUPropertyCollection _curObject;
        private UProperty _curProperty;
        private Stack<IUPropertyCollection> _objects;

        private int _spt;
        private int _indentLevel;
        private int _prevIndentLevel;

        private UYAMLParser()
        {
            _spt = 0;
            _objects = new Stack<IUPropertyCollection>();
            Reset();
        }

        /// <summary>Resets the state of the parser</summary>
        private void Reset()
        {
            _curObject = null;
            _curProperty = null;
            _objects.Clear();
            _indentLevel = 0;
            _prevIndentLevel = 0;
        }

        /// <summary>Parses the given UYAML content</summary>
        public static List<UComponent> Parse(string content)
        {
            int offset;
            int nextOffset;
            string block;

            // Get to first chunk
            offset = content.IndexOf(COMPONENT_HEADER);
            if (offset == -1)
                throw new System.InvalidOperationException("There was no blocks found");

            List<UComponent> components = new List<UComponent>();
            UYAMLParser parser = new UYAMLParser();

            do
            {
                nextOffset = content.IndexOf(COMPONENT_HEADER, offset + COMPONENT_HEADER.Length);
                if (nextOffset == -1)
                    block = content.Substring(offset);
                else
                    block = content.Substring(offset, nextOffset - offset-1);

                var component = parser.ParseComponent(block);
                components.Add(component);

                offset = nextOffset;
            } while (offset >= 0);

            return components;
        }

        private UComponent ParseComponent(string content)
        {
            Reset();
            int offset;
            int nextOffset;
            string line;

            // Get to the first line
            offset = content.IndexOf(COMPONENT_HEADER);
            if (offset == -1)
                throw new System.InvalidOperationException("The block is missing the content header");

            do
            {
                nextOffset = content.IndexOf('\n', offset)+1;
                if (nextOffset <= 0) line = content.Substring(offset);
                else line = content.Substring(offset, nextOffset - offset -1);

                ParseLine(line);

                offset = nextOffset;
            } while (offset > 0);

            while (_objects.TryPop(out var node))
            {
                if (node is UComponent comp)
                    return comp;
            }
            return null;
        }

        private void ParseLine(string content)
        {
            if (string.IsNullOrWhiteSpace(content))
                return;

            string line;
            bool isArrayEntry = false;

            _prevIndentLevel = _indentLevel;
            _indentLevel = Tabulate(content, out line);
            if (_spt < 1)  // Update the indentation level based of the first item we meet
            {
                _spt = _indentLevel;
                _indentLevel = Tabulate(content, out line);
            }


            // No block yet, expecting a new def
            if (_curObject == null)
            {
                if (!line.StartsWith(COMPONENT_HEADER))
                    throw new ParseException($"Expecting a new block, but got '{line}' instead.");

                string[] segs = line.Split(' ');
                if (segs.Length != 3)
                    throw new ParseException("Expecting 3 parts in the block header.");

                _curObject = new UComponent()
                {
                    classID = (UClassID) int.Parse(segs[1].Substring(3)),
                    fileID = long.Parse(segs[2].Substring(1))
                };
                return;
            }

            // Start of Array
            if (line[0] == '-')
            {
                line = line.Trim('-', '\t', ' ');
                _indentLevel++;
                isArrayEntry = true;
            }

            // Start of Object
            int indentDiff = _indentLevel - _prevIndentLevel;
            if (indentDiff == 1)    // Something wrong with this logic when adding item,s to array
            {
                if (isArrayEntry)
                {
                    // We have increased our indentation and we have started with a -,
                    // that means we starting an array and the parent property needs to be converted 
                    // into an array.

                    // We need to convert the current property to an array
                    var arr = new UArray();
                    _objects.Push(_curObject);
                    _curProperty.value = arr;
                    _curObject = arr;
                }
                else
                {
                    // Our indentation level has increased so we are making a new object
                    var obj = new UObject();
                    _objects.Push(_curObject);
                    _curProperty.value = obj;
                    _curObject = obj;
                }
            } 
            else if (indentDiff < 0)
            {
                while (_objects.Count > _indentLevel)
                    _curObject = _objects.Pop();
            } 
            else if (indentDiff != 0)
            {
                throw new ParseException("Indentation grew/shrunk too rapidly. Expected only a change of either 0 or 1.");
            }

            // Seperate the parts
            string[] parts = line.Split(':', 2);
            if (parts.Length == 1)
            {
                if (_curObject is UArray arr)
                    arr.Add(ParseValue(line));
                else
                    throw new ParseException("Cannot add key-less values to an object");
            }
            else
            {

                _curProperty = new UProperty();
                if (parts.Length != 2)
                    throw new ParseException($"Cannot find property name in '{line}'");
                _curProperty.name = parts[0].Trim();
                _curProperty.value = ParseValue(parts[1]);

                if (isArrayEntry)
                {
                    if (_curObject is not UArray && _objects.Peek() is UArray)
                        _curObject = _objects.Pop();

                    if (_curObject is UArray arr)
                    {
                        // Create a new object to put this property into
                        var obj = new UObject();
                        _objects.Push(_curObject);
                        _curObject = obj;
                        arr.Add(obj);
                    } 
                    else
                    {
                        throw new ParseException("Adding a new array item, but could not get an array to put it in.");
                    }
                }

                // Attempt to push the current property into the current object
                if (_curProperty != null && !_curObject.Add(_curProperty))
                    throw new ParseException($"Failed to add the property '{_curProperty.name}'");
            }

#if false
            // If we are in the middle of an array, we need to either add to the 
            //  array or build the items
            if (_curObject is UArray curArray)
            {
                // Seperate the parts
                bool isProperty = line.IndexOf(':') > 0;
                bool isInlineShape = line[0] == '{' || line[0] == '[';

                if (!isProperty && !isInlineShape)   // A single value, we will push it to the array directly
                {
                    if (!isArrayEntry)
                        throw new ParseException("Array Values must begin with -");
                    curArray.Add(ParseValue(line));
                }
                else if (isInlineShape)
                {
                    if (!isArrayEntry)
                        throw new ParseException("Array Values must begin with -");
                    curArray.Add(ParseValue(line));
                }
                else // An object for a value
                {
                    if (isArrayEntry) // Its a new item, so create the item and push it to the array.
                    {
                        var item = new UObject();
                        curArray.Add(item);
                    }

                    string[] parts = line.Split(':');
                    if (parts.Length == 2)  // If we have a name: value, add it to the last array item.
                    {
                        var lastItem = curArray.items[curArray.items.Count - 1];
                        if (lastItem is IUPropertyCollection propertyCollection)
                        {
                            var property = new UProperty()
                            {
                                name = parts[0].Trim(),
                                value = ParseValue(parts[1])
                            };

                            if (!propertyCollection.Add(property))
                                throw new ParseException($"Duplicate property found '{property.name}'");
                        }
                        else
                        {
                            throw new ParseException("Previous array item was not a property collection. Cannot add new properties.");
                        }
                    }
                }
            }
            else  // Adding a property to the previous object.
            {
                // Seperate the parts
                string[] parts = line.Split(':', 2);

                _curProperty = new UProperty();
                if (parts.Length != 2)
                    throw new ParseException($"Cannot find property name in '{line}'");
                _curProperty.name = parts[0].Trim();
                _curProperty.value = ParseValue(parts[1]);

                // Attempt to push the current property into the current object
                if (_curProperty != null && !_curObject.Add(_curProperty))
                    throw new ParseException($"Duplicate property found '{_curProperty.name}'");
            }
#endif
        }

        private UNode ParseValue(string value)
        {
            string[] parts;
            string content = value.Trim();

            if (content.Length == 0)
                return new UValue();

            if (content[0] == '{' && content[content.Length - 1] == '}') {
                UObject objValue = new UObject();
                if (content.Length > 2)
                {
                    parts = content.Split(',');
                    foreach (var part in parts)
                    {
                        string[] sParts = part.Trim('{', '}', ' ').Split(':', 2);
                        if (sParts.Length != 2)
                            throw new ParseException("Cannot parse non-key values inside a inline object!");
                        objValue.Add(new UProperty()
                        {
                            name = sParts[0].Trim(),
                            value = ParseValue(sParts[1])
                        });
                    }
                }
                return objValue;
            }

            if (content[0] == '[' && content[content.Length - 1] == ']') {
                UArray arrayValue = new UArray();
                if (content.Length > 2)
                {
                    parts = content.Split(',');
                    foreach (var part in parts)
                        arrayValue.Add(new UValue(part.Trim('[', ']', ' ')));
                }
                return arrayValue;
            }

            if (content[0] == '"' && content[content.Length - 1] == '"')
                content = content.Trim('"').Replace("\\\"", "\"");

            return new UValue(content);
        }


        private int Tabulate(string content, out string line)
        {
            int spaces;
            for (spaces = 0; spaces < content.Length; spaces++)
            {
                if (content[spaces] != ' ' && content[spaces] != '\t')
                    break;
            }

            line = content.TrimStart(' ', '\t', '\n', '\r');
            return spaces / Math.Max(_spt, 1);
        }
    }

    /// <summary>Represents errors that occure during parsing</summary>
    public sealed class ParseException : System.Exception
    {
        public ParseException(string message) : base(message) { }
    }

}

UYAMLWriter.cs

using System.Collections.Generic;
using System.Text;

namespace Lachee.Utilities.Serialization
{
    public class UYAMLWriter
    {
        private const string DEFAULT_EOL = "\r\n";
        private StringBuilder builder = new StringBuilder();

        private string eol = DEFAULT_EOL;

        public int IndentationSpaces { get; set; } = 2;
        public bool InlineObjects { get; set; } = true;
        public bool InlineComplexObjects { get; set; } = false;
        public bool InlineArrays { get; set; } = true;
        public bool InlineComplexArrays { get; set; } = false;

        public void AddComponets(IEnumerable<UComponent> components)
        {
            foreach (var component in components)
                AddComponent(component);
        }
        public void AddComponent(UComponent component)
        {
            builder.Append(UYAMLParser.COMPONENT_HEADER)
                .Append((int)component.classID)
                .Append(" &")
                .Append(component.fileID)
                .Append(eol);

            AppendProperty(component.Property, 0, false, false);
        }

        private void AppendProperty(UProperty property, int indent, bool arrayItem, bool skipIndent)
        {
            int indentLevel = indent;
            int indentSize = IndentationSpaces;
            string name = string.IsNullOrEmpty(property.name) ? "" : property.name + ":";

            if (arrayItem)
            {
                name = "-";
                indentLevel -= 1;
            }

            if (skipIndent)
                indentSize = 0;

            switch (property.value)
            {
                default: break;
                case UValue uValue:
                    builder.Append(' ', indentLevel * indentSize).Append(name).Append(" ").Append(uValue.value);
                    builder.Append(eol);
                    break;

                case UObject uObject:
                    if (CanInline(uObject) && !arrayItem)
                    {
                        builder.Append(' ', indentLevel * indentSize).Append(name).Append(" {");
                        eol = "";
                        bool first = true;
                        foreach (var kp in uObject.properties)
                        {
                            if (!first) builder.Append(", ");
                            AppendProperty(kp.Value, 0, false, true);
                            first = false;
                        }
                        eol = DEFAULT_EOL;
                        builder.Append('}').Append(eol);
                    }
                    else
                    {
                        bool first = true;
                        builder.Append(' ', indentLevel * indentSize).Append(name);
                        builder.Append(arrayItem ? ' ' : eol);  // This inlines the first time of an array
                        foreach (var kp in uObject.properties)
                        {
                            AppendProperty(kp.Value, indentLevel + 1, false, arrayItem && first);
                            first = false;
                        }
                    }
                    break;

                case UArray uArray:
                    if (CanInline(uArray))
                    {
                        builder.Append(' ', indentLevel * indentSize).Append(name).Append(" [");
                        eol = "";
                        bool first = true;
                        for (int i = 0; i < uArray.items.Count; i++)
                        {
                            if (!first) builder.Append(",");
                            AppendProperty(new UProperty() { value = uArray.items[i] }, 0, false, true);
                            first = false;
                        }

                        eol = DEFAULT_EOL;
                        builder.Append(']').Append(eol);
                    }
                    else
                    {
                        builder.Append(' ', indentLevel * indentSize).Append(name);
                        builder.Append(eol);
                        for (int i = 0; i < uArray.items.Count; i++)
                            AppendProperty(new UProperty() { value = uArray.items[i] }, indentLevel + 1, true, false);
                    }
                    break;
            }
        }

        private bool CanInline(UObject obj)
        {
            if (!InlineObjects)
                return false;

            if (obj.properties.Count == 0)
                return true;

            foreach(var kp in obj.properties)
            {
                if (InlineComplexObjects)
                {
                    if (kp.Value.value is UObject o && !CanInline(o))
                        return false;
                    if (kp.Value.value is UArray a && !CanInline(a))
                        return false;
                }
                else
                {
                    if (kp.Value.value is not UValue)
                        return false;
                }
            }

            return true;
        }

        private bool CanInline(UArray arr)
        {
            if (!InlineArrays) 
                return false;

            if (arr.items.Count == 0)
                return true;
            foreach(var item in arr.items)
            {
                if (InlineComplexArrays)
                {
                    if (item is UObject o && !CanInline(o))
                        return false;
                    if (item is UArray a && !CanInline(a))
                        return false;
                } 
                else 
                {
                    if (item is not UValue)
                        return false;
                }
            }
            return true;
        }

        public override string ToString()
            => $"%YAML 1.1{DEFAULT_EOL}%TAG !u! tag:unity3d.com,2011:{DEFAULT_EOL}" + builder.ToString();        
    }
}

License is MIT. I provide no warranty or liability for the code.

Updated version can be found https://github.com/Lachee/unity-utilities/tree/master/Runtime/UYAML