Merge pull request #469 from yoheimuta/mcp/468

Implement Model Context Protocol (MCP) server for protolint

Author: yoheimuta

README.md

@@ -23,10 +23,24 @@ protolint is the pluggable linting/fixing utility for Protocol Buffer files (pro
 
 ## Demo
 
-For example, vim-protolint works like the following.
+Once MCP server configured, you can ask any MCP clients like Claude Desktop to lint and fix your Protocol Buffer files like this:
+
+<img src="_doc/claude.gif" alt="demo" width="720"/>
+
+Also, vim-protolint works like the following.
 
 <img src="_doc/demo-v2.gif" alt="demo" width="600"/>
 
+## MCP Server
+protolint now includes support for the [Model Context Protocol (MCP)](https://modelcontextprotocol.io), which allows AI models to interact with protolint directly.
+
+### Usage
+```sh
+protolint --mcp
+```
+
+For detailed documentation on how to use and integrate protolint's MCP server functionality, see the [MCP documentation](./mcp/README.md).
+
 ## Installation
 
 ### Via Homebrew

_doc/claude.gif

@@ -8,6 +8,9 @@ import (
 
 // DEPRECATED: Use cmd/protolint. See https://github.com/yoheimuta/protolint/issues/20.
 func main() {
+	// Initialize the lint runner
+	cmd.Initialize()
+
 	os.Exit(int(
 		cmd.Do(
 			os.Args[1:],

cmd/pl/main.go

@@ -7,6 +7,9 @@ import (
 )
 
 func main() {
+	// Initialize the lint runner
+	cmd.Initialize()
+
 	os.Exit(int(
 		cmd.Do(
 			os.Args[1:],

cmd/protolint/main.go

@@ -8,6 +8,7 @@ import (
 	"github.com/yoheimuta/protolint/internal/cmd/subcmds/lint"
 	"github.com/yoheimuta/protolint/internal/cmd/subcmds/list"
 	"github.com/yoheimuta/protolint/internal/osutil"
+	"github.com/yoheimuta/protolint/mcp"
 )
 
 const (
@@ -17,6 +18,7 @@ Protocol Buffer Linter Command.
 Usage:
 	protolint <command> [arguments]
 	protolint --version
+	protolint --mcp
 
 The commands are:
 	lint     lint protocol buffer files
@@ -26,13 +28,15 @@ The commands are:
 The flags are:
 	--version  print protolint version
 	-v         print protolint version (when used as the only argument)
+	--mcp      start as an MCP server
 `
 )
 
 const (
 	subCmdLint    = "lint"
 	subCmdList    = "list"
 	subCmdVersion = "version"
+	mcpFlag       = "--mcp"
 )
 
 var (
@@ -46,11 +50,14 @@ func Do(
 	stdout io.Writer,
 	stderr io.Writer,
 ) osutil.ExitCode {
-	// Check for --version flag
+	// Check for --version and --mcp flags
 	for _, arg := range args {
 		if arg == "--version" || (arg == "-v" && len(args) == 1) {
 			return doVersion(stdout)
 		}
+		if arg == mcpFlag {
+			return doMCP(stdout, stderr)
+		}
 	}
 
 	switch {
@@ -146,3 +153,11 @@ func doVersion(
 	_, _ = fmt.Fprintln(stdout, "protolint version "+version+"("+revision+")")
 	return osutil.ExitSuccess
 }
+
+func doMCP(
+	stdout io.Writer,
+	stderr io.Writer,
+) osutil.ExitCode {
+	server := mcp.NewServer(stdout, stderr)
+	return server.Run()
+}

internal/cmd/cmd.go

@@ -0,0 +1,26 @@
+package cmd
+
+import (
+	"io"
+
+	"github.com/yoheimuta/protolint/internal/osutil"
+	"github.com/yoheimuta/protolint/lib"
+)
+
+// CmdLintRunner implements the lib.LintRunner interface for cmd package
+type CmdLintRunner struct{}
+
+// NewCmdLintRunner creates a new CmdLintRunner
+func NewCmdLintRunner() *CmdLintRunner {
+	return &CmdLintRunner{}
+}
+
+// Run executes the lint command
+func (r *CmdLintRunner) Run(args []string, stdout, stderr io.Writer) osutil.ExitCode {
+	return Do(args, stdout, stderr)
+}
+
+// Initialize registers the cmd lint runner with the lib package
+func Initialize() {
+	lib.SetLintRunner(NewCmdLintRunner())
+}

internal/cmd/lint_runner.go

@@ -97,6 +97,7 @@ func GetReporter(value string) (report.Reporter, error) {
 		"sarif":   reporters.SarifReporter{},
 		"sonar":   reporters.SonarReporter{},
 		"tsc":     reporters.TscReporter{},
+		"mcp":     reporters.MCPReporter{},
 		"ci":      reporters.NewCiReporterWithGenericFormat(),
 		"ci-az":   reporters.NewCiReporterForAzureDevOps(),
 		"ci-gh":   reporters.NewCiReporterForGithubActions(),
@@ -106,5 +107,5 @@ func GetReporter(value string) (report.Reporter, error) {
 	if r, ok := rs[value]; ok {
 		return r, nil
 	}
-	return nil, fmt.Errorf(`available reporters are "plain", "junit", "json", "sarif", and "unix, available reporters for CI/CD are ci, ci-az, ci-gh, ci-glab"`)
+	return nil, fmt.Errorf(`available reporters are "plain", "junit", "json", "sarif", "unix", "mcp", available reporters for CI/CD are ci, ci-az, ci-gh, ci-glab"`)
 }

internal/cmd/subcmds/lint/reporterFlag.go

@@ -0,0 +1,53 @@
+package reporters
+
+import (
+	"encoding/json"
+	"fmt"
+	"io"
+
+	"github.com/yoheimuta/protolint/linter/report"
+)
+
+// MCPReporter prints failures in MCP friendly JSON format.
+type MCPReporter struct{}
+
+// Report writes failures to w in MCP friendly format.
+func (r MCPReporter) Report(w io.Writer, fs []report.Failure) error {
+	// Group failures by file
+	fileFailures := make(map[string][]map[string]interface{})
+
+	for _, failure := range fs {
+		filePath := failure.Pos().Filename
+
+		failureInfo := map[string]interface{}{
+			"rule_id":  failure.RuleID(),
+			"message":  failure.Message(),
+			"line":     failure.Pos().Line,
+			"column":   failure.Pos().Column,
+			"severity": failure.Severity(),
+		}
+
+		fileFailures[filePath] = append(fileFailures[filePath], failureInfo)
+	}
+
+	// Convert to array of results
+	var fileResults []map[string]interface{} = []map[string]interface{}{}
+	for filePath, failures := range fileFailures {
+		fileResults = append(fileResults, map[string]interface{}{
+			"file_path": filePath,
+			"failures":  failures,
+		})
+	}
+
+	result := map[string]interface{}{
+		"results": fileResults,
+	}
+
+	bs, err := json.MarshalIndent(result, "", "  ")
+	if err != nil {
+		return err
+	}
+
+	_, err = fmt.Fprintln(w, string(bs))
+	return err
+}