Forward a bare --version after the package to the tool

src/Tests/ArgParserTests.cs

@@ -141,6 +141,100 @@ public void Version_with_a_value_and_no_package_is_still_an_error()
         Assert.Contains("PACKAGE_NAME", parsed.Error);
     }
 
+    [Theory]
+    [InlineData("stop", "--version")]
+    [InlineData("stop", "--VERSION")]
+    public void Bare_version_after_a_package_is_forwarded_to_the_tool(params string[] args)
+    {
+        var parsed = ArgParser.Parse(args);
+        var viaSeparator = ArgParser.Parse(args[0], "--", args[1]);
+
+        Assert.True(parsed.Success);
+        Assert.False(parsed.ShowVersion);
+        Assert.Equal("stop", parsed.PackageId);
+        Assert.Null(parsed.Version);
+        Assert.Equal(viaSeparator.ForwardedArguments, parsed.ForwardedArguments);
+        Assert.Equal([args[1]], parsed.ForwardedArguments);
+    }
+
+    [Fact]
+    public void Bare_version_after_a_pinned_package_keeps_the_pin_and_forwards()
+    {
+        var parsed = ArgParser.Parse("stop@1.2.3", "--version");
+
+        Assert.True(parsed.Success);
+        Assert.Equal("stop", parsed.PackageId);
+        Assert.Equal("1.2.3", parsed.Version);
+        Assert.Equal(["--version"], parsed.ForwardedArguments);
+    }
+
+    [Fact]
+    public void Bare_version_after_other_options_still_forwards_only_the_flag()
+    {
+        var parsed = ArgParser.Parse(
+            "stop", "--prerelease", "--source", "https://feed.example", "--version");
+
+        Assert.True(parsed.Success);
+        Assert.False(parsed.ShowVersion);
+        Assert.Equal("stop", parsed.PackageId);
+        Assert.Null(parsed.Version);
+        Assert.True(parsed.Prerelease);
+        Assert.Equal(["https://feed.example"], parsed.Sources);
+        Assert.Equal(["--version"], parsed.ForwardedArguments);
+    }
+
+    [Fact]
+    public void Version_value_after_a_package_still_selects_that_version()
+    {
+        var parsed = ArgParser.Parse("stop", "--version", "1.2.3", "--", "--version");
+
+        Assert.True(parsed.Success);
+        Assert.Equal("stop", parsed.PackageId);
+        Assert.Equal("1.2.3", parsed.Version);
+        Assert.Equal(["--version"], parsed.ForwardedArguments);
+    }
+
+    [Fact]
+    public void Second_bare_version_is_forwarded_when_the_first_already_has_a_value()
+    {
+        var parsed = ArgParser.Parse("stop", "--version", "1.2.3", "--version");
+
+        Assert.True(parsed.Success);
+        Assert.Equal("1.2.3", parsed.Version);
+        Assert.Equal(["--version"], parsed.ForwardedArguments);
+    }
+
+    [Theory]
+    [InlineData("--yes", "--version")]
+    [InlineData("--update", "--version")]
+    [InlineData("--update", "1.2.3", "--version")]
+    public void Bare_version_without_a_package_still_requires_a_value(params string[] args)
+    {
+        var parsed = ArgParser.Parse(args);
+
+        Assert.False(parsed.Success);
+        Assert.False(parsed.ShowVersion);
+        Assert.Contains("Missing value for --version", parsed.Error);
+    }
+
+    [Fact]
+    public void Version_followed_by_another_token_is_still_that_tokens_value()
+    {
+        var parsed = ArgParser.Parse("stop", "--version", "--help");
+
+        Assert.False(parsed.Success);
+        Assert.Contains("Invalid version '--help'", parsed.Error);
+    }
+
+    [Fact]
+    public void Empty_version_assignment_is_still_missing_a_value()
+    {
+        var parsed = ArgParser.Parse("stop", "--version=");
+
+        Assert.False(parsed.Success);
+        Assert.Contains("Missing value for --version", parsed.Error);
+    }
+
     [Fact]
     public void Update_alone_is_a_self_update_to_latest()
     {

src/ndx/ArgParser.cs

@@ -4,7 +4,9 @@ namespace ndx;
 /// dnx.cmd-compatible argv split: first operand is PACKAGE[@VERSION], listed
 /// flags are consumed by ndx, everything else (including tokens after --) is
 /// forwarded to the child. <c>--update [VERSION]</c> is a standalone self-update.
-/// A lone <c>--version</c> prints the ndx version.
+/// A lone <c>--version</c> prints the ndx version. After a package id, a
+/// <c>--version</c> with no value is forwarded to the tool, as in
+/// <c>ndx stop -- --version</c>.
 /// </summary>
 public static class ArgParser
 {
@@ -106,7 +108,18 @@ public static Invocation Parse(IReadOnlyList<string> args)
                 if (value is null)
                 {
                     if (i + 1 >= args.Count)
+                    {
+                        // `ndx stop --version` names the tool, not a package version.
+                        // A following token is still the value (`--version 1.2.3`,
+                        // or an invalid one such as `--version --help`).
+                        if (IsVersionOption(option) && packageId is not null && !update)
+                        {
+                            forwarded.Add(arg);
+                            continue;
+                        }
+
                         return Invocation.Failed($"Missing value for {option}.");
+                    }
 
                     value = args[++i];
                 }
@@ -332,11 +345,12 @@ static bool TryParseIdentity(string token, out string? packageId, out string? ve
     static bool IsBareVersionFlag(string token)
     {
         var (option, inline) = SplitOption(token);
-        return option is not null
-            && option.Equals("--version", StringComparison.OrdinalIgnoreCase)
-            && inline is null;
+        return IsVersionOption(option) && inline is null;
     }
 
+    static bool IsVersionOption(string? option)
+        => option is not null && option.Equals("--version", StringComparison.OrdinalIgnoreCase);
+
     static (string? Name, string? InlineValue) SplitOption(string token)
     {
         if (token.Length < 2 || token[0] != '-')