feat: add --fail-on option to control failing severity

src/Dolphin/Cli/CheckCommand.cs

@@ -31,23 +31,32 @@ public static Command Build()
             description: "Scan only this file instead of the entire project"
         );
 
+        var failOnOption = new Option<string>(
+            "--fail-on",
+            description: "Lowest severity that causes a non-zero exit: error, warning, or info",
+            getDefaultValue: () => "error"
+        );
+        failOnOption.FromAmong("error", "warning", "info");
+
         var cmd = new Command("check", "Run static analysis rules against the codebase")
         {
             cwdOption,
             ruleOption,
             formatOption,
-            fileOption
+            fileOption,
+            failOnOption
         };
 
         cmd.SetHandler(
-            async (cwd, ruleId, format, file) =>
-                Environment.Exit(await HandleAsync(cwd, ruleId, format, file)),
-            cwdOption, ruleOption, formatOption, fileOption);
+            async (cwd, ruleId, format, file, failOn) =>
+                Environment.Exit(await HandleAsync(cwd, ruleId, format, file, failOn)),
+            cwdOption, ruleOption, formatOption, fileOption, failOnOption);
 
         return cmd;
     }
 
-    internal static async Task<int> HandleAsync(string cwd, string? ruleId, string format, string? file)
+    internal static async Task<int> HandleAsync(
+        string cwd, string? ruleId, string format, string? file, string failOn = "error")
     {
         cwd = Path.GetFullPath(cwd);
         if (!Directory.Exists(cwd))
@@ -113,6 +122,18 @@ internal static async Task<int> HandleAsync(string cwd, string? ruleId, string f
 
         Formatter.Print(result.Findings, format);
 
-        return result.Findings.Any(f => f.Severity == Severity.Error) ? 1 : 0;
+        var threshold = failOn.ToLowerInvariant();
+        return result.Findings.Any(f => Fails(f.Severity, threshold)) ? 1 : 0;
     }
+
+    // Whether a finding of the given severity should cause a non-zero exit under the
+    // configured threshold (which must already be lower-cased). Listed explicitly so
+    // behavior does not depend on the Severity enum's declaration order.
+    private static bool Fails(Severity severity, string threshold) =>
+        threshold switch
+        {
+            "info" => true,
+            "warning" => severity is Severity.Error or Severity.Warning,
+            _ => severity == Severity.Error
+        };
 }

tests/Dolphin.Tests/CheckCommandTests.cs

@@ -1,3 +1,4 @@
+using System.CommandLine;
 using System.Diagnostics;
 using System.Text.Json;
 using Dolphin.Cli;
@@ -10,6 +11,25 @@ public class CheckCommandTests
 {
     // ── Unit tests ─────────────────────────────────────────────────────────────
 
+    [TestMethod]
+    public void Build_FailOnOption_DefaultsToError()
+    {
+        var cmd = CheckCommand.Build();
+        var result = cmd.Parse("");
+        var option = (Option<string>)cmd.Options.Single(o => o.Name == "fail-on");
+        Assert.AreEqual("error", result.GetValueForOption(option));
+    }
+
+    [TestMethod]
+    public void Build_FailOnOption_AcceptsValidValuesAndRejectsInvalid()
+    {
+        var cmd = CheckCommand.Build();
+        var option = (Option<string>)cmd.Options.Single(o => o.Name == "fail-on");
+
+        Assert.AreEqual("warning", cmd.Parse("--fail-on warning").GetValueForOption(option));
+        Assert.IsTrue(cmd.Parse("--fail-on bogus").Errors.Count > 0);
+    }
+
     [TestMethod]
     public async Task HandleAsync_NonExistentCwd_Returns2()
     {
@@ -53,6 +73,72 @@ public async Task HandleAsync_FakeScanner_NoFindings_Returns0()
         }
     }
 
+    private const string WarningFindingJson =
+        """{"results":[{"check_id":"r","path":"f.ts","start":{"line":1,"col":1},"end":{"line":1,"col":1},"extra":{"message":"m","severity":"WARNING","lines":"x"}}]}""";
+
+    [TestMethod]
+    public async Task HandleAsync_WarningFinding_DefaultFailOn_Returns0()
+    {
+        if (OperatingSystem.IsWindows()) Assert.Inconclusive("Fake scanner uses a shell script; Unix-only");
+        var (tmpDir, fakeBinDir) = CreateFakeOpengrepEnv(exitCode: 1, stdout: WarningFindingJson);
+        var savedPath = Environment.GetEnvironmentVariable("PATH");
+        Environment.SetEnvironmentVariable("PATH", fakeBinDir + ":" + savedPath);
+        try
+        {
+            var result = await CheckCommand.HandleAsync(tmpDir, null, "text", null);
+            Assert.AreEqual(0, result);
+        }
+        finally
+        {
+            Environment.SetEnvironmentVariable("PATH", savedPath);
+            Directory.Delete(tmpDir, recursive: true);
+            Directory.Delete(fakeBinDir, recursive: true);
+        }
+    }
+
+    [TestMethod]
+    public async Task HandleAsync_WarningFinding_FailOnWarning_Returns1()
+    {
+        if (OperatingSystem.IsWindows()) Assert.Inconclusive("Fake scanner uses a shell script; Unix-only");
+        var (tmpDir, fakeBinDir) = CreateFakeOpengrepEnv(exitCode: 1, stdout: WarningFindingJson);
+        var savedPath = Environment.GetEnvironmentVariable("PATH");
+        Environment.SetEnvironmentVariable("PATH", fakeBinDir + ":" + savedPath);
+        try
+        {
+            var result = await CheckCommand.HandleAsync(tmpDir, null, "text", null, "warning");
+            Assert.AreEqual(1, result);
+        }
+        finally
+        {
+            Environment.SetEnvironmentVariable("PATH", savedPath);
+            Directory.Delete(tmpDir, recursive: true);
+            Directory.Delete(fakeBinDir, recursive: true);
+        }
+    }
+
+    private const string InfoFindingJson =
+        """{"results":[{"check_id":"r","path":"f.ts","start":{"line":1,"col":1},"end":{"line":1,"col":1},"extra":{"message":"m","severity":"INFO","lines":"x"}}]}""";
+
+    [TestMethod]
+    public async Task HandleAsync_InfoFinding_FailOnInfo_Returns1()
+    {
+        if (OperatingSystem.IsWindows()) Assert.Inconclusive("Fake scanner uses a shell script; Unix-only");
+        var (tmpDir, fakeBinDir) = CreateFakeOpengrepEnv(exitCode: 1, stdout: InfoFindingJson);
+        var savedPath = Environment.GetEnvironmentVariable("PATH");
+        Environment.SetEnvironmentVariable("PATH", fakeBinDir + ":" + savedPath);
+        try
+        {
+            var result = await CheckCommand.HandleAsync(tmpDir, null, "text", null, "info");
+            Assert.AreEqual(1, result);
+        }
+        finally
+        {
+            Environment.SetEnvironmentVariable("PATH", savedPath);
+            Directory.Delete(tmpDir, recursive: true);
+            Directory.Delete(fakeBinDir, recursive: true);
+        }
+    }
+
     [TestMethod]
     public async Task HandleAsync_FakeScanner_ScannerWarning_Returns0()
     {