Minimal DacFx repro: PublishChangesToProject emits a duplicate ALTER TABLE ADD CONSTRAINT for a constraint already defined inline in CREATE TABLE. Reproduces on both Microsoft.Build.Sql SDK and legacy SSDT projects with DacFx 170.4.80-preview.

Program.cs

// Minimal self-contained repro for DacFx issue:
// SchemaComparisonResult.PublishChangesToProject emits a redundant
// trailing ALTER TABLE ADD CONSTRAINT for a constraint already defined
// inline within CREATE TABLE.
//
// Usage:
//   dotnet run -- [server] [sa-password]
// Defaults: server=localhost,11433  password=MpleoDevTools_Pwd1!

using Microsoft.Data.SqlClient;
using Microsoft.SqlServer.Dac;
using Microsoft.SqlServer.Dac.Compare;

class Program
{
    const string LegacySqlproj = """
        <?xml version="1.0" encoding="utf-8"?>
        <Project DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003" ToolsVersion="4.0">
          <PropertyGroup>
            <Name>Repro</Name>
            <SchemaVersion>2.0</SchemaVersion>
            <ProjectVersion>4.1</ProjectVersion>
            <ProjectGuid>{11111111-1111-1111-1111-111111111111}</ProjectGuid>
            <DSP>Microsoft.Data.Tools.Schema.Sql.Sql160DatabaseSchemaProvider</DSP>
            <OutputType>Database</OutputType>
            <DefaultCollation>SQL_Latin1_General_CP1_CI_AS</DefaultCollation>
            <ModelCollation>1033, CI</ModelCollation>
          </PropertyGroup>
          <ItemGroup>
            <Build Include="dbo\Tables\Demo.sql" />
          </ItemGroup>
          <Import Project="$(MSBuildExtensionsPath)\Microsoft\VisualStudio\v$(VisualStudioVersion)\SSDT\Microsoft.Data.Tools.Schema.SqlTasks.targets" />
        </Project>
        """;

    const string SdkSqlproj = """
        <?xml version="1.0" encoding="utf-8"?>
        <Project DefaultTargets="Build">
          <Sdk Name="Microsoft.Build.Sql" Version="2.1.0" />
          <PropertyGroup>
            <Name>Repro</Name>
            <ProjectGuid>{22222222-2222-2222-2222-222222222222}</ProjectGuid>
            <DSP>Microsoft.Data.Tools.Schema.Sql.Sql160DatabaseSchemaProvider</DSP>
            <ModelCollation>1033, CI</ModelCollation>
            <DefaultCollation>SQL_Latin1_General_CP1_CI_AS</DefaultCollation>
          </PropertyGroup>
        </Project>
        """;

    static int Main(string[] args)
    {
        var server = args.Length > 0 ? args[0] : "localhost,11433";
        var saPwd  = args.Length > 1 ? args[1] : "MpleoDevTools_Pwd1!";

        var workDir = Path.Combine(Path.GetTempPath(), "DacFxRepro_" + Guid.NewGuid().ToString("N")[..8]);
        Directory.CreateDirectory(workDir);
        Console.WriteLine($"Work dir: {workDir}");

        var dbName = "DacFxReproDb_" + Guid.NewGuid().ToString("N")[..8];
        var masterConn = $"Server={server};User Id=sa;Password={saPwd};Encrypt=False;TrustServerCertificate=True";
        var dbConn     = $"Server={server};User Id=sa;Password={saPwd};Database={dbName};Encrypt=False;TrustServerCertificate=True";

        Exec(masterConn, $"CREATE DATABASE [{dbName}];");
        try
        {
            // Live DB starts with the same shape the project will start with:
            // a 2-column table, no inline DEFAULT.
            Exec(dbConn, """
                CREATE TABLE [dbo].[Demo] (
                    [Id]   INT NOT NULL PRIMARY KEY,
                    [Flag] BIT NOT NULL
                );
                """);

            RunScenario("LEGACY", LegacySqlproj, workDir, dbConn);

            // Reset DB for the next scenario.
            Exec(dbConn, "DROP TABLE [dbo].[Demo]; CREATE TABLE [dbo].[Demo] ([Id] INT NOT NULL PRIMARY KEY, [Flag] BIT NOT NULL);");

            RunScenario("SDK", SdkSqlproj, workDir, dbConn);
        }
        finally
        {
            try { Exec(masterConn, $"ALTER DATABASE [{dbName}] SET SINGLE_USER WITH ROLLBACK IMMEDIATE; DROP DATABASE [{dbName}];"); } catch { }
        }
        return 0;
    }

    static void RunScenario(string label, string sqlprojXml, string baseDir, string dbConn)
    {
        Console.WriteLine();
        Console.WriteLine($"=========== {label} ===========");

        var dir = Path.Combine(baseDir, label);
        Directory.CreateDirectory(Path.Combine(dir, "dbo", "Tables"));

        var sqlprojPath = Path.Combine(dir, "Repro.sqlproj");
        File.WriteAllText(sqlprojPath, sqlprojXml);

        // Project starts with 2 columns and no DEFAULT — matches DB state.
        var tablePath = Path.Combine(dir, "dbo", "Tables", "Demo.sql");
        File.WriteAllText(tablePath, """
            CREATE TABLE [dbo].[Demo] (
                [Id]   INT NOT NULL PRIMARY KEY,
                [Flag] BIT NOT NULL
            );
            """);

        Console.WriteLine($"[{label}] Target project: {sqlprojPath}");
        Console.WriteLine($"[{label}] Initial Demo.sql:");
        PrintIndented(File.ReadAllText(tablePath));

        var dsp = "Microsoft.Data.Tools.Schema.Sql.Sql160DatabaseSchemaProvider";
        var scripts = new[] { tablePath };

        // Mutate the DB so it has an additional column + inline DEFAULT
        // that the project doesn't have. DacFx should add both to the
        // project — but it should add the DEFAULT only ONCE.
        Exec(dbConn, """
            ALTER TABLE [dbo].[Demo] ADD [Note] NVARCHAR(50) NULL CONSTRAINT [DF_Demo_Note] DEFAULT ('hello');
            """);

        var source = new SchemaCompareDatabaseEndpoint(dbConn);
        var target = new SchemaCompareProjectEndpoint(sqlprojPath, scripts, dsp, DacExtractTarget.SchemaObjectType);
        var cmp = new SchemaComparison(source, target);
        var result = cmp.Compare();
        Console.WriteLine($"[{label}] Compare: {result.Differences?.Count() ?? 0} difference(s).");

        var publish = result.PublishChangesToProject(dir, DacExtractTarget.SchemaObjectType);
        Console.WriteLine($"[{label}] PublishChangesToProject.Success = {publish.Success}");
        if (!publish.Success)
        {
            Console.WriteLine($"[{label}] Error: {publish.ErrorMessage}");
            return;
        }
        Console.WriteLine($"[{label}] Added:   {string.Join(", ", publish.AddedFiles)}");
        Console.WriteLine($"[{label}] Changed: {string.Join(", ", publish.ChangedFiles)}");
        Console.WriteLine($"[{label}] Deleted: {string.Join(", ", publish.DeletedFiles)}");

        var after = File.ReadAllText(tablePath);
        Console.WriteLine($"[{label}] Demo.sql AFTER publish:");
        PrintIndented(after);

        var inlineHit     = after.Contains("CONSTRAINT [DF_Demo_Note] DEFAULT");
        var standaloneHit = after.Contains("ADD CONSTRAINT [DF_Demo_Note]");
        Console.WriteLine($"[{label}] Inline CONSTRAINT [DF_Demo_Note] present:   {inlineHit}");
        Console.WriteLine($"[{label}] Standalone ADD CONSTRAINT [DF_Demo_Note]:   {standaloneHit}");
        Console.WriteLine($"[{label}] >>> BUG: " + (inlineHit && standaloneHit
            ? "REPRODUCED — duplicate constraint emitted."
            : "not reproduced in this run."));
    }

    static void Exec(string connStr, string sql)
    {
        using var conn = new SqlConnection(connStr);
        conn.Open();
        using var cmd = new SqlCommand(sql, conn) { CommandTimeout = 60 };
        cmd.ExecuteNonQuery();
    }

    static void PrintIndented(string text)
    {
        foreach (var line in text.Replace("\r", "").Split('\n'))
            Console.WriteLine("    " + line);
    }
}

Repro.csproj

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>net10.0</TargetFramework>
    <Nullable>enable</Nullable>
    <ImplicitUsings>enable</ImplicitUsings>
    <RollForward>LatestMajor</RollForward>
  </PropertyGroup>
  <ItemGroup>
    <PackageReference Include="Microsoft.SqlServer.DacFx" Version="170.4.80-preview" />
    <PackageReference Include="Microsoft.Data.SqlClient" Version="7.0.1" />
  </ItemGroup>
</Project>