feat: implement :serverlist command by dlevy-msft-sql · Pull Request #630 · microsoft/go-sqlcmd

dlevy-msft-sql · 2026-01-25T03:51:37Z

Summary

Implements the :serverlist interactive command to list available SQL Server instances via the SQL Browser service.

Changes

Add :serverlist command that queries the SQL Browser service (UDP port 1434)
Move server listing logic from cmd/sqlcmd/sqlcmd.go to pkg/sqlcmd/serverlist.go for reuse
Both -L flag and :serverlist command now use the shared ListLocalServers() function
Add comprehensive tests for parsing SQL Browser responses

Usage

# From command line
sqlcmd -L

# In interactive mode
1> :serverlist

Motivation

ODBC sqlcmd supports the :serverlist command to discover SQL Server instances. This brings go-sqlcmd to parity with that functionality.

Testing

Added unit tests for parseInstances() function
Added integration test for :serverlist command
All existing tests pass

Copilot

Pull request overview

This PR implements the :serverlist interactive command to discover SQL Server instances via the SQL Browser service, bringing go-sqlcmd to feature parity with ODBC sqlcmd.

Changes:

Added :serverlist command that queries the SQL Browser service on UDP port 1434
Refactored server listing logic from cmd/sqlcmd/sqlcmd.go to pkg/sqlcmd/serverlist.go for code reuse
Both the -L command-line flag and :serverlist command now share the ListLocalServers() function

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 4 comments.

File	Description
pkg/sqlcmd/serverlist.go	New file containing refactored server listing functions (`ListLocalServers`, `GetLocalServerInstances`, `parseInstances`)
pkg/sqlcmd/serverlist_test.go	New test file with comprehensive tests for server listing and parsing functionality
pkg/sqlcmd/commands.go	Added `SERVERLIST` command registration and `serverlistCommand` handler function
cmd/sqlcmd/sqlcmd.go	Removed `listLocalServers` and `parseInstances` functions (moved to pkg/sqlcmd), updated `-L` flag to use `sqlcmd.ListLocalServers()`

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

pkg/sqlcmd/serverlist.go

pkg/sqlcmd/commands.go

pkg/sqlcmd/serverlist.go

- Rename variables to follow Go naming conventions: - out_s -> outStr - got_name -> gotName - instdict -> instanceDict - Add argument validation to serverlistCommand

Copilot

Pull request overview

Copilot reviewed 6 out of 6 changed files in this pull request and generated 6 comments.

pkg/sqlcmd/serverlist.go

pkg/sqlcmd/commands.go

pkg/sqlcmd/commands_test.go

Copilot

Pull request overview

Copilot reviewed 6 out of 6 changed files in this pull request and generated 5 comments.

pkg/sqlcmd/serverlist.go

pkg/sqlcmd/commands.go

pkg/sqlcmd/commands_test.go

pkg/sqlcmd/serverlist.go

README.md

Copilot

Pull request overview

Copilot reviewed 6 out of 6 changed files in this pull request and generated 1 comment.

pkg/sqlcmd/commands.go

Copilot

Pull request overview

Copilot reviewed 6 out of 6 changed files in this pull request and generated no new comments.

Copilot

Pull request overview

Copilot reviewed 6 out of 6 changed files in this pull request and generated 1 comment.

Copilot · 2026-01-25T21:42:01Z

pkg/sqlcmd/serverlist.go

+	_, err = conn.Write(bmsg)
+	if err != nil {
+		// Silently ignore errors, same as ODBC
+		return nil
+	}
+	read, err := conn.Read(resp)
+	if err != nil {
+		// Silently ignore errors, same as ODBC
+		return nil
+	}


The error handling behavior has changed from the previous implementation. The old code in cmd/sqlcmd/sqlcmd.go printed non-timeout errors to stdout before returning. The new implementation silently ignores all errors. While the comment states this matches ODBC behavior, this represents a user-visible behavior change where network errors (connection refused, permission denied, etc.) that were previously visible to users are now completely silent. Consider whether this is the intended behavior or if at least some classes of errors should still be logged or returned.

Copilot

Pull request overview

Copilot reviewed 6 out of 6 changed files in this pull request and generated 6 comments.

Copilot · 2026-01-25T23:20:09Z

README.md

+MYSERVER\SQL2019
+MYSERVER\SQL2022


The example output shown here does not include the two-space indentation that the actual implementation produces. The code in ListLocalServers (serverlist.go:28) formats the output as " %s\n" with two leading spaces. The documentation should accurately show this formatting or the code should be updated to match the documentation.

Suggested change

MYSERVER\SQL2019

MYSERVER\SQL2022

MYSERVER\SQL2019

MYSERVER\SQL2022

Copilot · 2026-01-25T23:20:09Z

README.md

+To capture stderr separately (for error logging):
+```batch
+sqlcmd -Q ":serverlist" 2>errors.log > servers.txt
+if exist errors.log if not "%%~z errors.log"=="0" type errors.log


This batch script has a syntax error. The file size test operator %~z only works within a FOR loop context, not directly in an IF statement. A correct alternative would be to use FOR /F to check the file size, or simply check if the file exists and has content using: "if exist errors.log (for %%A in (errors.log) do if %%~zA GTR 0 type errors.log)"

Suggested change

if exist errors.log if not "%%~z errors.log"=="0" type errors.log

if exist errors.log (for %%A in (errors.log) do if %%~zA GTR 0 type errors.log)

Copilot · 2026-01-25T23:20:09Z

pkg/sqlcmd/serverlist.go

+func ListLocalServers(w io.Writer) {
+	instances, err := GetLocalServerInstances()
+	if err != nil {
+		fmt.Fprintln(os.Stderr, err)


Writing errors directly to os.Stderr creates an inconsistency with the rest of the sqlcmd architecture. When serverlistCommand calls ListLocalServers with s.GetOutput(), errors will bypass the configured error stream (s.GetError()). Consider either: (1) accepting an error writer parameter alongside the output writer, or (2) returning the error and letting the caller handle it. This would make error handling consistent with other commands like connectCommand which use s.GetError() or return errors to be handled by the framework.

Suggested change

fmt.Fprintln(os.Stderr, err)

fmt.Fprintln(w, err)

Copilot · 2026-01-25T23:20:09Z

pkg/sqlcmd/serverlist.go

+					if len(instanceDict) == 0 {
+						break
+					}
+					// Only add if InstanceName key exists and is non-empty


The validation added here (checking if InstanceName exists and is non-empty) is a good improvement over the old implementation. However, consider adding a comment explaining why instances without InstanceName should be skipped, as this represents a defensive measure against malformed SQL Browser responses.

Suggested change

// Only add if InstanceName key exists and is non-empty

// Only add if InstanceName key exists and is non-empty.

// This defensively skips malformed or partial SQL Browser responses

// that do not include a valid InstanceName for an instance.

Copilot · 2026-01-25T23:20:10Z

pkg/sqlcmd/serverlist_test.go

+func TestParseInstances(t *testing.T) {
+	// Test parsing of SQL Browser response
+	// Format: 0x05 (response type), 2 bytes length, then semicolon-separated key=value pairs
+	// Each instance ends with two semicolons
+
+	t.Run("empty response", func(t *testing.T) {
+		result := parseInstances([]byte{})
+		assert.Empty(t, result)
+	})
+
+	t.Run("invalid header", func(t *testing.T) {
+		result := parseInstances([]byte{1, 0, 0})
+		assert.Empty(t, result)
+	})
+
+	t.Run("valid single instance", func(t *testing.T) {
+		// Simulating SQL Browser response format
+		// Header: 0x05 followed by 2 length bytes, then the instance data
+		data := []byte{5, 0, 0}
+		instanceData := "ServerName;MYSERVER;InstanceName;MSSQLSERVER;IsClustered;No;Version;15.0.2000.5;tcp;1433;;"
+		data = append(data, []byte(instanceData)...)
+
+		result := parseInstances(data)
+		assert.Len(t, result, 1)
+		assert.Contains(t, result, "MSSQLSERVER")
+		assert.Equal(t, "MYSERVER", result["MSSQLSERVER"]["ServerName"])
+		assert.Equal(t, "1433", result["MSSQLSERVER"]["tcp"])
+	})
+
+	t.Run("valid multiple instances", func(t *testing.T) {
+		data := []byte{5, 0, 0}
+		instanceData := "ServerName;MYSERVER;InstanceName;MSSQLSERVER;tcp;1433;;ServerName;MYSERVER;InstanceName;SQLEXPRESS;tcp;1434;;"
+		data = append(data, []byte(instanceData)...)
+
+		result := parseInstances(data)
+		assert.Len(t, result, 2)
+		assert.Contains(t, result, "MSSQLSERVER")
+		assert.Contains(t, result, "SQLEXPRESS")
+	})
+}


Consider adding a test case for an instance with a missing or empty ServerName to verify that the new validation logic in parseInstances correctly filters out such instances. This would test the defensive behavior added in lines 109-112 of serverlist.go.

Copilot · 2026-01-25T23:20:10Z

README.md

+MYSERVER\SQL2019
+MYSERVER\SQL2022


The example output doesn't show the behavior when the default MSSQLSERVER instance is present. According to the code (serverlist.go:82-83), the default instance produces two entries in the output: "(local)" and the actual server name (e.g., "MYSERVER"). Consider adding an example showing this case, such as " (local)\n MYSERVER\n MYSERVER\SQL2019".

Suggested change

MYSERVER\SQL2019

MYSERVER\SQL2022

(local)

MYSERVER

MYSERVER\SQL2019

- :serverlist queries SQL Browser service (UDP 1434) to discover instances - :help displays available sqlcmd commands - Refactored server listing logic to pkg/sqlcmd/serverlist.go for reuse by both -L flag and :serverlist command

- :serverlist queries SQL Browser service (UDP 1434) to discover instances - :help displays available sqlcmd commands - Refactored server listing logic to pkg/sqlcmd/serverlist.go for reuse

dlevy-msft-sql requested a review from Copilot January 25, 2026 04:03

Copilot started reviewing on behalf of dlevy-msft-sql January 25, 2026 04:03 View session

Copilot AI reviewed Jan 25, 2026

View reviewed changes

pkg/sqlcmd/serverlist.go Outdated Show resolved Hide resolved

pkg/sqlcmd/commands.go Outdated Show resolved Hide resolved

pkg/sqlcmd/serverlist.go Outdated Show resolved Hide resolved

pkg/sqlcmd/serverlist.go Outdated Show resolved Hide resolved

dlevy-msft-sql added this to the ODBC SQLCMD Interchangeability milestone Jan 25, 2026

dlevy-msft-sql mentioned this pull request Jan 25, 2026

feat: round out ODBC sqlcmd compatibility with missing features and fixes #623

Closed

dlevy-msft-sql mentioned this pull request Jan 25, 2026

Implement :help command #634

Closed

dlevy-msft-sql requested a review from Copilot January 25, 2026 18:12

Copilot started reviewing on behalf of dlevy-msft-sql January 25, 2026 18:12 View session

Copilot AI reviewed Jan 25, 2026

View reviewed changes

dlevy-msft-sql requested a review from Copilot January 25, 2026 19:05

Copilot started reviewing on behalf of dlevy-msft-sql January 25, 2026 19:05 View session

Copilot AI reviewed Jan 25, 2026

View reviewed changes

pkg/sqlcmd/serverlist.go Outdated Show resolved Hide resolved

pkg/sqlcmd/commands.go Outdated Show resolved Hide resolved

pkg/sqlcmd/commands_test.go Outdated Show resolved Hide resolved

pkg/sqlcmd/serverlist.go Outdated Show resolved Hide resolved

README.md Show resolved Hide resolved

dlevy-msft-sql requested a review from Copilot January 25, 2026 19:49

Copilot started reviewing on behalf of dlevy-msft-sql January 25, 2026 19:50 View session

Copilot AI reviewed Jan 25, 2026

View reviewed changes

pkg/sqlcmd/commands.go Outdated Show resolved Hide resolved

dlevy-msft-sql requested a review from Copilot January 25, 2026 20:10

Copilot started reviewing on behalf of dlevy-msft-sql January 25, 2026 20:11 View session

Copilot AI reviewed Jan 25, 2026

View reviewed changes

dlevy-msft-sql requested a review from Copilot January 25, 2026 21:38

Copilot started reviewing on behalf of dlevy-msft-sql January 25, 2026 21:38 View session

Copilot AI reviewed Jan 25, 2026

View reviewed changes

dlevy-msft-sql self-assigned this Jan 25, 2026

dlevy-msft-sql added sqlcmd switch switch in existing sqlcmd Size: S Small issue (less than one week effort) labels Jan 25, 2026

dlevy-msft-sql requested a review from Copilot January 25, 2026 23:14

Copilot started reviewing on behalf of dlevy-msft-sql January 25, 2026 23:14 View session

Copilot AI reviewed Jan 25, 2026

View reviewed changes

dlevy-msft-sql added the in-review label Feb 2, 2026

dlevy-msft-sql force-pushed the serverlist-command branch from c103e26 to db48592 Compare February 5, 2026 18:31

dlevy-msft-sql force-pushed the serverlist-command branch from db48592 to 5bc6080 Compare February 5, 2026 18:58

feat: implement :serverlist and :help interactive commands

8fd1d8f

- :serverlist queries SQL Browser service (UDP 1434) to discover instances - :help displays available sqlcmd commands - Refactored server listing logic to pkg/sqlcmd/serverlist.go for reuse

dlevy-msft-sql force-pushed the serverlist-command branch from 5bc6080 to 8fd1d8f Compare February 5, 2026 19:54

dlevy-msft-sql changed the title ~~Implement :serverlist command~~ feat: implement :serverlist command Feb 5, 2026

Merge branch 'main' into serverlist-command

1af7232

dlevy-msft-sql removed the in-review label Feb 6, 2026

	if exist errors.log if not "%%~z errors.log"=="0" type errors.log
	if exist errors.log (for %%A in (errors.log) do if %%~zA GTR 0 type errors.log)

-					// Only add if InstanceName key exists and is non-empty
+					// Only add if InstanceName key exists and is non-empty.
+					// This defensively skips malformed or partial SQL Browser responses
+					// that do not include a valid InstanceName for an instance.

Conversation

dlevy-msft-sql commented Jan 25, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Summary

Changes

Usage

Motivation

Testing

Uh oh!

Copilot AI left a comment

Choose a reason for hiding this comment

Pull request overview

Reviewed changes

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Copilot AI left a comment

Choose a reason for hiding this comment

Pull request overview

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Copilot AI left a comment

Choose a reason for hiding this comment

Pull request overview

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Copilot AI left a comment

Choose a reason for hiding this comment

Pull request overview

Uh oh!

Uh oh!

Copilot AI left a comment

Choose a reason for hiding this comment

Pull request overview

Uh oh!

Copilot AI left a comment

Choose a reason for hiding this comment

Pull request overview

Uh oh!

Copilot AI Jan 25, 2026

Choose a reason for hiding this comment

Uh oh!

Copilot AI left a comment

Choose a reason for hiding this comment

Pull request overview

Uh oh!

Copilot AI Jan 25, 2026

Choose a reason for hiding this comment

Uh oh!

Copilot AI Jan 25, 2026

Choose a reason for hiding this comment

Uh oh!

Copilot AI Jan 25, 2026

Choose a reason for hiding this comment

Uh oh!

Copilot AI Jan 25, 2026

Choose a reason for hiding this comment

Uh oh!

Copilot AI Jan 25, 2026

Choose a reason for hiding this comment

Uh oh!

Copilot AI Jan 25, 2026

Choose a reason for hiding this comment

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

dlevy-msft-sql commented Jan 25, 2026 •

edited

Loading