aspnetcore/test/Microsoft.AspNetCore.Mvc.ViewFeatures.Test/Rendering/HtmlHelperDisplayTextTest.cs

// Copyright (c) .NET Foundation. All rights reserved.
// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.

using Microsoft.AspNetCore.Mvc.ModelBinding;
using Xunit;

namespace Microsoft.AspNetCore.Mvc.Rendering
{
    /// <summary>
    /// Test the <see cref="IHtmlHelper.DisplayText"/> and
    /// <see cref="IHtmlHelper{TModel}.DisplayTextFor{TValue}"/> methods.
    /// </summary>
    public class HtmlHelperDisplayTextTest
    {
        [Fact]
        public void DisplayText_ReturnsEmpty_IfValueNull()
        {
            // Arrange
            var helper = DefaultTemplatesUtilities.GetHtmlHelper<OverriddenToStringModel>(model: null);

            // Act
            var result = helper.DisplayText(expression: string.Empty);

            // Assert
            Assert.Empty(result);
        }

        [Fact]
        public void DisplayTextFor_ReturnsEmpty_IfValueNull()
        {
            // Arrange
            var helper = DefaultTemplatesUtilities.GetHtmlHelper<OverriddenToStringModel>(model: null);

            // Act
            var result = helper.DisplayTextFor(m => m);

            // Assert
            Assert.Empty(result);
        }

        [Fact]
        public void DisplayText_ReturnsNullDisplayText_IfSetAndValueNull()
        {
            // Arrange
            var provider = new TestModelMetadataProvider();
            provider.ForType<OverriddenToStringModel>().DisplayDetails(dd =>
            {
                dd.NullDisplayText = "Null display Text";
            });

            var helper = DefaultTemplatesUtilities.GetHtmlHelper<OverriddenToStringModel>(model: null, provider: provider);

            // Act
            var result = helper.DisplayText(expression: string.Empty);

            // Assert
            Assert.Equal("Null display Text", result);
        }

        [Fact]
        public void DisplayTextFor_ReturnsNullDisplayText_IfSetAndValueNull()
        {
            // Arrange
            var provider = new TestModelMetadataProvider();
            provider.ForType<OverriddenToStringModel>().DisplayDetails(dd =>
            {
                dd.NullDisplayText = "Null display Text";
            });

            var helper = DefaultTemplatesUtilities.GetHtmlHelper<OverriddenToStringModel>(model: null, provider: provider);

            // Act
            var result = helper.DisplayTextFor(m => m);

            // Assert
            Assert.Equal("Null display Text", result);
        }

        [Fact]
        public void DisplayText_ReturnsValue_IfNameEmpty()
        {
            // Arrange
            var model = new OverriddenToStringModel("Model value");
            var helper = DefaultTemplatesUtilities.GetHtmlHelper(model);

            // Act
            var result = helper.DisplayText(expression: string.Empty);
            var nullResult = helper.DisplayText(expression: null);    // null is another alias for current model

            // Assert
            Assert.Equal("Model value", result);
            Assert.Equal("Model value", nullResult);
        }

        [Fact]
        public void DisplayText_ReturnsEmpty_IfNameNotFound()
        {
            // Arrange
            var model = new OverriddenToStringModel("Model value");
            var helper = DefaultTemplatesUtilities.GetHtmlHelper(model);

            // Act
            var result = helper.DisplayText("NonExistentProperty");

            // Assert
            Assert.Empty(result);
        }

        [Fact]
        public void DisplayTextFor_ReturnsValue_IfIdentityExpression()
        {
            // Arrange
            var model = new OverriddenToStringModel("Model value");
            var helper = DefaultTemplatesUtilities.GetHtmlHelper(model);

            // Act
            var result = helper.DisplayTextFor(m => m);

            // Assert
            Assert.Equal("Model value", result);
        }

        [Fact]
        public void DisplayText_ReturnsSimpleDisplayText_IfSetAndValueNonNull()
        {
            // Arrange
            var model = new OverriddenToStringModel("Ignored text")
            {
                SimpleDisplay = "Simple display text",
            };

            var provider = new TestModelMetadataProvider();
            provider.ForType<OverriddenToStringModel>().DisplayDetails(dd =>
            {
                dd.SimpleDisplayProperty = nameof(OverriddenToStringModel.SimpleDisplay);
            });

            var helper = DefaultTemplatesUtilities.GetHtmlHelper<OverriddenToStringModel>(model: model, provider: provider);

            // Act
            var result = helper.DisplayText(expression: string.Empty);

            // Assert
            Assert.Equal("Simple display text", result);
        }

        [Fact]
        public void DisplayTextFor_ReturnsSimpleDisplayText_IfSetAndValueNonNull()
        {
            // Arrange
            var model = new OverriddenToStringModel("Ignored text")
            {
                SimpleDisplay = "Simple display text",
            };

            var provider = new TestModelMetadataProvider();
            provider.ForType<OverriddenToStringModel>().DisplayDetails(dd =>
            {
                dd.SimpleDisplayProperty = nameof(OverriddenToStringModel.SimpleDisplay);
            });

            var helper = DefaultTemplatesUtilities.GetHtmlHelper<OverriddenToStringModel>(model: model, provider: provider);

            // Act
            var result = helper.DisplayTextFor(m => m);

            // Assert
            Assert.Equal("Simple display text", result);
        }

        [Fact]
        public void DisplayText_ReturnsPropertyValue_IfNameFound()
        {
            // Arrange
            var model = new OverriddenToStringModel("Ignored text")
            {
                Name = "Property value",
                SimpleDisplay = "Simple display text",
            };

            var provider = new TestModelMetadataProvider();
            provider.ForType<OverriddenToStringModel>().DisplayDetails(dd =>
            {
                dd.SimpleDisplayProperty = nameof(OverriddenToStringModel.SimpleDisplay);
            });

            var helper = DefaultTemplatesUtilities.GetHtmlHelper<OverriddenToStringModel>(model: model, provider: provider);

            // Act
            var result = helper.DisplayText("Name");

            // Assert
            Assert.Equal("Property value", result);
        }

        [Fact]
        public void DisplayTextFor_ReturnsPropertyValue_IfPropertyExpression()
        {
            // Arrange
            var model = new OverriddenToStringModel("ignored text")
            {
                Name = "Property value",
            };
            var helper = DefaultTemplatesUtilities.GetHtmlHelper(model);

            // Act
            var result = helper.DisplayTextFor(m => m.Name);

            // Assert
            Assert.Equal("Property value", result);
        }

        [Fact]
        public void DisplayText_ReturnsViewDataEntry()
        {
            // Arrange
            var model = new OverriddenToStringModel("Model value")
            {
                Name = "Property value",
            };
            var helper = DefaultTemplatesUtilities.GetHtmlHelper(model);
            helper.ViewData["Name"] = "View data dictionary value";

            // Act
            var result = helper.DisplayText("Name");

            // Assert
            Assert.Equal("View data dictionary value", result);
        }

        [Fact]
        public void DisplayTextFor_IgnoresViewDataEntry()
        {
            // Arrange
            var model = new OverriddenToStringModel("Model value")
            {
                Name = "Property value",
            };
            var helper = DefaultTemplatesUtilities.GetHtmlHelper(model);
            helper.ViewData["Name"] = "View data dictionary value";

            // Act
            var result = helper.DisplayTextFor(m => m.Name);

            // Assert
            Assert.Equal("Property value", result);
        }

        [Fact]
        public void DisplayText_IgnoresModelStateEntry_ReturnsViewDataEntry()
        {
            // Arrange
            var model = new OverriddenToStringModel("Model value")
            {
                Name = "Property value",
            };
            var helper = DefaultTemplatesUtilities.GetHtmlHelper(model);
            var viewData = helper.ViewData;
            viewData["FieldPrefix.Name"] = "View data dictionary value";
            viewData.TemplateInfo.HtmlFieldPrefix = "FieldPrefix";

            viewData.ModelState.SetModelValue(
                "FieldPrefix.Name",
                "Attempted name value",
                "Attempted name value");

            // Act
            var result = helper.DisplayText("Name");

            // Assert
            Assert.Equal("View data dictionary value", result);
        }

        [Fact]
        public void DisplayTextFor_IgnoresModelStateEntry()
        {
            // Arrange
            var model = new OverriddenToStringModel("Model value")
            {
                Name = "Property value",
            };
            var helper = DefaultTemplatesUtilities.GetHtmlHelper(model);
            var viewData = helper.ViewData;
            viewData["Name"] = "View data dictionary value";
            viewData.TemplateInfo.HtmlFieldPrefix = "FieldPrefix";

            viewData.ModelState.SetModelValue(
                "FieldPrefix.Name",
                "Attempted name value",
                "Attempted name value");

            // Act
            var result = helper.DisplayTextFor(m => m.Name);

            // Assert
            Assert.Equal("Property value", result);
        }

        // ModelMetadata.SimpleDisplayText returns ToString() result if that method has been overridden.
        private sealed class OverriddenToStringModel
        {
            private readonly string _simpleDisplayText;

            public OverriddenToStringModel(string simpleDisplayText)
            {
                _simpleDisplayText = simpleDisplayText;
            }

            public string SimpleDisplay { get; set; }

            public string Name { get; set; }

            public override string ToString()
            {
                return _simpleDisplayText;
            }
        }
    }
}