Blazor column placeholder (#1967)

# Pull Request

## 🤨 Rationale

Adds Blazor support for column placeholders, which is part of #1538.

## 👩‍💻 Implementation

Add `Placeholder` to the 5 columns that support that property.

## 🧪 Testing

Added unit tests

## ✅ Checklist

<!--- Review the list and put an x in the boxes that apply or ~~strike
through~~ around items that don't (along with an explanation). -->

- [ ] I have updated the project documentation to reflect my changes or
determined no changes are needed.

change/@ni-nimble-blazor-8ccc91d3-f08e-4f36-a4a8-2f9a750c026d.json

@@ -0,0 +1,7 @@
+{
+  "type": "minor",
+  "comment": "Add support for column placeholders",
+  "packageName": "@ni/nimble-blazor",
+  "email": "20542556+mollykreis@users.noreply.github.com",
+  "dependentChangeType": "patch"
+}

packages/nimble-blazor/NimbleBlazor/Components/NimbleTableColumnAnchor.razor

@@ -4,6 +4,7 @@
 <nimble-table-column-anchor
     label-field-name="@LabelFieldName"
     href-field-name="@HrefFieldName"
+    placeholder="@Placeholder"
     appearance="@Appearance.ToAttributeValue()"
     underline-hidden="@UnderlineHidden"
     hreflang="@HrefLang"

packages/nimble-blazor/NimbleBlazor/Components/NimbleTableColumnAnchor.razor.cs

@@ -19,6 +19,12 @@ public partial class NimbleTableColumnAnchor : NimbleTableColumn, IFractionalWid
     [DisallowNull]
     public string HrefFieldName { get; set; } = null!;
 
+    /// <summary>
+    /// The placeholder text to display when the label and href are both null for a record.
+    /// </summary>
+    [Parameter]
+    public string? Placeholder { get; set; }
+
     /// <summary>
     /// The appearance of the anchor.
     /// </summary>

packages/nimble-blazor/NimbleBlazor/Components/NimbleTableColumnDateText.razor

@@ -4,6 +4,7 @@
 <nimble-table-column-date-text
     column-id="@ColumnId"
     field-name="@FieldName"
+    placeholder="@Placeholder"
     action-menu-slot="@ActionMenuSlot"
     action-menu-label="@ActionMenuLabel"
     column-hidden="@ColumnHidden"

packages/nimble-blazor/NimbleBlazor/Components/NimbleTableColumnDateText.razor.cs

@@ -12,6 +12,12 @@ public partial class NimbleTableColumnDateText : NimbleTableColumn, IFractionalW
     [DisallowNull]
     public string FieldName { get; set; } = null!;
 
+    /// <summary>
+    /// The placeholder text to display when the field value is null for a record.
+    /// </summary>
+    [Parameter]
+    public string? Placeholder { get; set; }
+
     /// <summary>
     /// The fractional/proportional width to use for this column
     /// </summary>

packages/nimble-blazor/NimbleBlazor/Components/NimbleTableColumnDurationText.razor

@@ -4,6 +4,7 @@
 <nimble-table-column-duration-text
     column-id="@ColumnId"
     field-name="@FieldName"
+    placeholder="@Placeholder"
     action-menu-slot="@ActionMenuSlot"
     action-menu-label="@ActionMenuLabel"
     column-hidden="@ColumnHidden"

packages/nimble-blazor/NimbleBlazor/Components/NimbleTableColumnDurationText.razor.cs

@@ -12,6 +12,12 @@ public partial class NimbleTableColumnDurationText : NimbleTableColumn, IFractio
     [DisallowNull]
     public string FieldName { get; set; } = null!;
 
+    /// <summary>
+    /// The placeholder text to display when the field value is null for a record.
+    /// </summary>
+    [Parameter]
+    public string? Placeholder { get; set; }
+
     /// <summary>
     /// The fractional/proportional width to use for this column
     /// </summary>

packages/nimble-blazor/NimbleBlazor/Components/NimbleTableColumnNumberText.razor

@@ -4,6 +4,7 @@
 <nimble-table-column-number-text
     column-id="@ColumnId"
     field-name="@FieldName"
+    placeholder="@Placeholder"
     action-menu-slot="@ActionMenuSlot"
     action-menu-label="@ActionMenuLabel"
     column-hidden="@ColumnHidden"

packages/nimble-blazor/NimbleBlazor/Components/NimbleTableColumnNumberText.razor.cs

@@ -12,6 +12,12 @@ public partial class NimbleTableColumnNumberText : NimbleTableColumn, IFractiona
     [DisallowNull]
     public string FieldName { get; set; } = null!;
 
+    /// <summary>
+    /// The placeholder text to display when the field value is null for a record.
+    /// </summary>
+    [Parameter]
+    public string? Placeholder { get; set; }
+
     /// <summary>
     /// The fractional/proportional width to use for this column
     /// </summary>

packages/nimble-blazor/NimbleBlazor/Components/NimbleTableColumnText.razor

@@ -4,6 +4,7 @@
 <nimble-table-column-text
     column-id="@ColumnId"
     field-name="@FieldName"
+    placeholder="@Placeholder"
     action-menu-slot="@ActionMenuSlot"
     action-menu-label="@ActionMenuLabel"
     column-hidden="@ColumnHidden"

packages/nimble-blazor/NimbleBlazor/Components/NimbleTableColumnText.razor.cs

@@ -12,6 +12,12 @@ public partial class NimbleTableColumnText : NimbleTableColumn, IFractionalWidth
     [DisallowNull]
     public string FieldName { get; set; } = null!;
 
+    /// <summary>
+    /// The placeholder text to display when the field value is null for a record.
+    /// </summary>
+    [Parameter]
+    public string? Placeholder { get; set; }
+
     /// <summary>
     /// The fractional/proportional width to use for this column
     /// </summary>

packages/nimble-blazor/Tests/NimbleBlazor.Tests/Unit/Components/NimbleTableColumnAnchorTests.cs

@@ -46,6 +46,15 @@ public void NimbleTableColumnAnchor_WithAppearanceAttribute_HasTableMarkup()
         Assert.Contains(expectedMarkup, tableColumn.Markup);
     }
 
+    [Fact]
+    public void NimbleTableColumnAnchor_WithPlaceholderAttribute_HasTableMarkup()
+    {
+        var table = RenderWithPropertySet(x => x.Placeholder, "Custom placeholder");
+
+        var expectedMarkup = @"placeholder=""Custom placeholder""";
+        Assert.Contains(expectedMarkup, table.Markup);
+    }
+
     [Fact]
     public void NimbleTableColumnAnchor_WithUnderlineHiddenAttribute_HasTableMarkup()
     {

packages/nimble-blazor/Tests/NimbleBlazor.Tests/Unit/Components/NimbleTableColumnDateTextTests.cs

@@ -28,6 +28,15 @@ public void NimbleTableColumnDateText_WithFieldNameAttribute_HasTableMarkup()
         Assert.Contains(expectedMarkup, table.Markup);
     }
 
+    [Fact]
+    public void NimbleTableColumnDateText_WithPlaceholderAttribute_HasTableMarkup()
+    {
+        var table = RenderWithPropertySet(x => x.Placeholder, "Custom placeholder");
+
+        var expectedMarkup = @"placeholder=""Custom placeholder""";
+        Assert.Contains(expectedMarkup, table.Markup);
+    }
+
     [Theory]
     [InlineData(DateTextFormat.Default, "<nimble-table-column-date-text((?!format).)*>")]
     [InlineData(DateTextFormat.Custom, @"format=""custom""")]

packages/nimble-blazor/Tests/NimbleBlazor.Tests/Unit/Components/NimbleTableColumnDurationTextTests.cs

@@ -28,6 +28,15 @@ public void NimbleTableColumnDurationText_WithFieldNameAttribute_HasTableMarkup(
         Assert.Contains(expectedMarkup, table.Markup);
     }
 
+    [Fact]
+    public void NimbleTableColumnDurationText_WithPlaceholderAttribute_HasTableMarkup()
+    {
+        var table = RenderWithPropertySet(x => x.Placeholder, "Custom placeholder");
+
+        var expectedMarkup = @"placeholder=""Custom placeholder""";
+        Assert.Contains(expectedMarkup, table.Markup);
+    }
+
     private IRenderedComponent<NimbleTableColumnDurationText> RenderWithPropertySet<TProperty>(Expression<Func<NimbleTableColumnDurationText, TProperty>> propertyGetter, TProperty propertyValue)
     {
         var context = new TestContext();

packages/nimble-blazor/Tests/NimbleBlazor.Tests/Unit/Components/NimbleTableColumnNumberTextTests.cs

@@ -28,6 +28,15 @@ public void NimbleTableColumnNumberText_WithFieldNameAttribute_HasTableMarkup()
         Assert.Contains(expectedMarkup, table.Markup);
     }
 
+    [Fact]
+    public void NimbleTableColumnNumberText_WithPlaceholderAttribute_HasTableMarkup()
+    {
+        var table = RenderWithPropertySet(x => x.Placeholder, "Custom placeholder");
+
+        var expectedMarkup = @"placeholder=""Custom placeholder""";
+        Assert.Contains(expectedMarkup, table.Markup);
+    }
+
     [Fact]
     public void NimbleTableColumnNumberText_WithDecimalDigitsAttribute_HasTableMarkup()
     {

packages/nimble-blazor/Tests/NimbleBlazor.Tests/Unit/Components/NimbleTableColumnTextTests.cs

@@ -28,6 +28,15 @@ public void NimbleTableColumnText_WithFieldNameAttribute_HasTableMarkup()
         Assert.Contains(expectedMarkup, table.Markup);
     }
 
+    [Fact]
+    public void NimbleTableColumnText_WithPlaceholderAttribute_HasTableMarkup()
+    {
+        var table = RenderWithPropertySet(x => x.Placeholder, "Custom placeholder");
+
+        var expectedMarkup = @"placeholder=""Custom placeholder""";
+        Assert.Contains(expectedMarkup, table.Markup);
+    }
+
     private IRenderedComponent<NimbleTableColumnText> RenderWithPropertySet<TProperty>(Expression<Func<NimbleTableColumnText, TProperty>> propertyGetter, TProperty propertyValue)
     {
         var context = new TestContext();