Plan viewer: show each warning's actionable fix, and take severity colours from one helper

Darling/Darling.Tests/PlanViewerWarningColorAndFixTests.cs

@@ -0,0 +1,90 @@
+/*
+ * Copyright (c) 2026 Erik Darling, Darling Data LLC
+ *
+ * This file is part of the SQL Server Performance Monitor.
+ *
+ * Licensed under the MIT License. See LICENSE file in the project root for full license information.
+ */
+
+using System;
+using System.IO;
+using PerformanceMonitor.PlanAnalysis;
+using Xunit;
+
+namespace Darling.Tests;
+
+/// <summary>
+/// #4572: <see cref="PlanWarningDisplay.WarningSeverityColorHex"/> is the one place a warning's
+/// severity becomes a colour, replacing three duplicated ternaries in
+/// <c>PlanViewerControl.Properties.cs</c> and <c>PlanViewerControl.Tooltips.cs</c>. Also pins that
+/// the properties panel now renders <see cref="PlanWarning.ActionableFix"/> under each warning
+/// message. The colour-helper assertions are compile-only RED on dev (the member doesn't exist);
+/// the source-census assertion is a runtime RED on dev (the old ternaries are still there).
+/// </summary>
+public sealed class PlanViewerWarningColorAndFixTests
+{
+    [Fact]
+    public void WarningSeverityColorHex_Critical_IsRed() =>
+        Assert.Equal("#E57373", PlanWarningDisplay.WarningSeverityColorHex(PlanWarningSeverity.Critical));
+
+    [Fact]
+    public void WarningSeverityColorHex_Warning_IsAmber() =>
+        Assert.Equal("#FFB347", PlanWarningDisplay.WarningSeverityColorHex(PlanWarningSeverity.Warning));
+
+    [Fact]
+    public void WarningSeverityColorHex_Info_IsBlue() =>
+        Assert.Equal("#6BB5FF", PlanWarningDisplay.WarningSeverityColorHex(PlanWarningSeverity.Info));
+
+    [Fact]
+    public void PlanWarning_WithActionableFix_CarriesTheFixText()
+    {
+        var warning = new PlanWarning
+        {
+            WarningType = "Serial Plan",
+            Message = "This operator ran single-threaded.",
+            ActionableFix = "Consider raising cost threshold for parallelism."
+        };
+
+        Assert.Equal("Consider raising cost threshold for parallelism.", warning.ActionableFix);
+    }
+
+    [Fact]
+    public void PlanWarning_WithoutActionableFix_IsNull()
+    {
+        var warning = new PlanWarning { WarningType = "Local Variables", Message = "Uses a local variable." };
+
+        Assert.Null(warning.ActionableFix);
+    }
+
+    /// <summary>
+    /// No inline severity-colour hex literal is left in the WPF viewer control: every site resolves
+    /// through <see cref="PlanWarningDisplay.WarningSeverityColorHex"/> instead of repeating the
+    /// ternary. RED on dev, where the three sites (plan warnings, node warnings, tooltip warnings)
+    /// each still spell out "#E57373"/"#FFB347"/"#6BB5FF" directly.
+    /// </summary>
+    [Fact]
+    public void PlanViewerControl_HasNoInlineSeverityColorLiterals()
+    {
+        var repoRoot = FindRepoRoot();
+        var uiDir = Path.Combine(repoRoot, "PerformanceMonitor.Ui");
+        Assert.True(Directory.Exists(uiDir), $"Expected {uiDir} to exist.");
+
+        foreach (var file in Directory.EnumerateFiles(uiDir, "PlanViewerControl.*.cs"))
+        {
+            var text = File.ReadAllText(file);
+            Assert.DoesNotContain("#E57373", text, StringComparison.Ordinal);
+            Assert.DoesNotContain("#FFB347", text, StringComparison.Ordinal);
+            Assert.DoesNotContain("#6BB5FF", text, StringComparison.Ordinal);
+        }
+    }
+
+    private static string FindRepoRoot()
+    {
+        var dir = new DirectoryInfo(AppContext.BaseDirectory);
+        while (dir is not null && !File.Exists(Path.Combine(dir.FullName, "PerformanceMonitor.sln")))
+            dir = dir.Parent;
+
+        Assert.NotNull(dir);
+        return dir!.FullName;
+    }
+}

PerformanceMonitor.PlanAnalysis/PlanWarningDisplay.cs

@@ -54,6 +54,16 @@ private static string WarningSourceTag(PlanWarning warning) =>
     private static string FormatBenefitPercent(double pct) =>
         pct >= 100 ? $"{pct:N0}" : $"{pct:N1}";
 
+    /// <summary>
+    /// #4572: the one place a warning's severity becomes a colour. Mirrors PerformanceStudio's
+    /// <c>WarningSeverityBrush</c> (one helper instead of the same ternary repeated at every
+    /// warning-rendering site), but keeps PM's existing literal hex values rather than PS's theme
+    /// tokens, so this change carries no visual difference.
+    /// </summary>
+    public static string WarningSeverityColorHex(PlanWarningSeverity severity) =>
+        severity == PlanWarningSeverity.Critical ? "#E57373"
+        : severity == PlanWarningSeverity.Warning ? "#FFB347" : "#6BB5FF";
+
     /// <summary>
     /// #4534: the text the viewer needs to turn a warning header into a link to the operator it came
     /// from. Null when <paramref name="originNodeIds"/> is empty — a finding with no known operator

PerformanceMonitor.Ui/PlanViewerControl.Properties.cs

@@ -813,8 +813,7 @@ private void ShowPropertiesPanel(PlanNode node)
                 AddPropertySection("Plan Warnings");
                 foreach (var w in PlanWarningDisplay.OrderByBenefit(s.PlanWarnings))
                 {
-                    var warnColor = w.Severity == PlanWarningSeverity.Critical ? "#E57373"
-                        : w.Severity == PlanWarningSeverity.Warning ? "#FFB347" : "#6BB5FF";
+                    var warnColor = PlanWarningDisplay.WarningSeverityColorHex(w.Severity);
                     var warnPanel = new StackPanel { Margin = new Thickness(10, 2, 10, 2) };
                     var planWarnHeaderText = PlanWarningDisplay.PlanWarningHeader(w);
                     var planWarnHeaderBlock = new TextBlock
@@ -834,6 +833,18 @@ private void ShowPropertiesPanel(PlanNode node)
                         TextWrapping = TextWrapping.Wrap,
                         Margin = new Thickness(16, 0, 0, 0)
                     });
+                    if (!string.IsNullOrEmpty(w.ActionableFix))
+                    {
+                        warnPanel.Children.Add(new TextBlock
+                        {
+                            Text = w.ActionableFix,
+                            FontSize = 11,
+                            FontStyle = FontStyles.Italic,
+                            Foreground = TooltipFgBrush,
+                            TextWrapping = TextWrapping.Wrap,
+                            Margin = new Thickness(16, 2, 0, 0)
+                        });
+                    }
                     (_currentPropertySection ?? PropertiesContent).Children.Add(warnPanel);
                 }
             }
@@ -857,8 +868,7 @@ private void ShowPropertiesPanel(PlanNode node)
             AddPropertySection("Warnings");
             foreach (var w in PlanWarningDisplay.OrderByBenefit(node.Warnings))
             {
-                var warnColor = w.Severity == PlanWarningSeverity.Critical ? "#E57373"
-                    : w.Severity == PlanWarningSeverity.Warning ? "#FFB347" : "#6BB5FF";
+                var warnColor = PlanWarningDisplay.WarningSeverityColorHex(w.Severity);
                 var warnPanel = new StackPanel { Margin = new Thickness(10, 2, 10, 2) };
                 var opWarnHeaderText = PlanWarningDisplay.PlanWarningHeader(w);
                 var opWarnHeaderBlock = new TextBlock
@@ -878,6 +888,18 @@ private void ShowPropertiesPanel(PlanNode node)
                     TextWrapping = TextWrapping.Wrap,
                     Margin = new Thickness(16, 0, 0, 0)
                 });
+                if (!string.IsNullOrEmpty(w.ActionableFix))
+                {
+                    warnPanel.Children.Add(new TextBlock
+                    {
+                        Text = w.ActionableFix,
+                        FontSize = 11,
+                        FontStyle = FontStyles.Italic,
+                        Foreground = TooltipFgBrush,
+                        TextWrapping = TextWrapping.Wrap,
+                        Margin = new Thickness(16, 2, 0, 0)
+                    });
+                }
                 PropertiesContent.Children.Add(warnPanel);
             }
         }

PerformanceMonitor.Ui/PlanViewerControl.Tooltips.cs

@@ -181,8 +181,7 @@ private ToolTip BuildNodeTooltip(PlanNode node, List<PlanWarning>? allWarnings =
 
                 foreach (var (type, severity, count) in distinct)
                 {
-                    var warnColor = severity == PlanWarningSeverity.Critical ? "#E57373"
-                        : severity == PlanWarningSeverity.Warning ? "#FFB347" : "#6BB5FF";
+                    var warnColor = PlanWarningDisplay.WarningSeverityColorHex(severity);
                     var label = count > 1 ? $"\u26A0 {type} ({count})" : $"\u26A0 {type}";
                     stack.Children.Add(new TextBlock
                     {
@@ -198,8 +197,7 @@ private ToolTip BuildNodeTooltip(PlanNode node, List<PlanWarning>? allWarnings =
                 // Individual node: show full warning messages
                 foreach (var w in warnings)
                 {
-                    var warnColor = w.Severity == PlanWarningSeverity.Critical ? "#E57373"
-                        : w.Severity == PlanWarningSeverity.Warning ? "#FFB347" : "#6BB5FF";
+                    var warnColor = PlanWarningDisplay.WarningSeverityColorHex(w.Severity);
                     stack.Children.Add(new TextBlock
                     {
                         Text = $"\u26A0 {w.WarningType}: {w.Message}",