tool = "go_file_context"

if err := writeFileSummary(ctx, snapshot, pgf.URI, &result, false, nil); err != nil {

if err := writeFileSummary(ctx, snapshot, file.URI, &result, false, nil); err != nil {

if err := writeFileSummary(ctx, snapshot, f, &buf, true, nil); err != nil {

func writeFileSummary(ctx context.Context, snapshot *cache.Snapshot, f protocol.DocumentURI, out *strings.Builder, onlyExported bool, declsToSummarize map[string]bool) error {

// If we're summarizing specific declarations, we don't need to copy the header.

if declsToSummarize == nil {

// Copy everything before the first non-import declaration:

// package decl, imports decl(s), and all comments (excluding copyright).

{

endPos := pgf.File.FileEnd

outerloop:

for _, decl := range pgf.File.Decls {

switch decl := decl.(type) {

case *ast.FuncDecl:

if decl.Doc != nil {

endPos = decl.Doc.Pos()

} else {

endPos = decl.Pos()

}

break outerloop

case *ast.GenDecl:

if decl.Tok == token.IMPORT {

continue

}

if decl.Doc != nil {

endPos = decl.Doc.Pos()

} else {

endPos = decl.Pos()

}

break outerloop

startPos := pgf.File.FileStart

if copyright := golang.CopyrightComment(pgf.File); copyright != nil {

startPos = copyright.End()

}

text, err := pgf.PosText(startPos, endPos)

if err != nil {

return err

}

out.Write(bytes.TrimSpace(text))

out.WriteString("\n\n")

}

if declsToSummarize != nil {

if _, ok := declsToSummarize[decl.Name.Name]; !ok {

continue

}

}

// If we are summarizing specific decls, check if any of them are in this GenDecl.

if declsToSummarize != nil {

found := false

for _, spec := range decl.Specs {

switch spec := spec.(type) {

case *ast.TypeSpec:

if _, ok := declsToSummarize[spec.Name.Name]; ok {

found = true

}

case *ast.ValueSpec:

for _, name := range spec.Names {

if _, ok := declsToSummarize[name.Name]; ok {

found = true

}

}

}

}

if !found {

continue

}

}

if declsToSummarize != nil {

if _, ok := declsToSummarize[spec.Name.Name]; !ok {

continue

}

}

if declsToSummarize != nil {

found := false

for _, name := range spec.Names {

if _, ok := declsToSummarize[name.Name]; ok {

found = true

}

}

if !found {

continue

}

}

package mcp

import (

"context"

"fmt"

"go/ast"

"go/types"

"strings"

"golang.org/x/tools/gopls/internal/golang"

"golang.org/x/tools/gopls/internal/protocol"

"golang.org/x/tools/internal/mcp"

)

type fileContextParams struct {

File string `json:"file"`

}

func (h *handler) fileContextTool() *mcp.ServerTool {

return mcp.NewServerTool(

"go_file_context",

"Summarizes a file's cross-file dependencies",

h.fileContextHandler,

mcp.Input(

mcp.Property("file", mcp.Description("the absolute path to the file")),

),

)

}

func (h *handler) fileContextHandler(ctx context.Context, _ *mcp.ServerSession, params *mcp.CallToolParamsFor[fileContextParams]) (*mcp.CallToolResultFor[any], error) {

fh, snapshot, release, err := h.fileOf(ctx, params.Arguments.File)

if err != nil {

return nil, err

}

defer release()

pkg, pgf, err := golang.NarrowestPackageForFile(ctx, snapshot, fh.URI())

if err != nil {

return nil, err

}

info := pkg.TypesInfo()

if info == nil {

return nil, fmt.Errorf("no types info for package %q", pkg.Metadata().PkgPath)

}

// Group objects defined in other files by file URI.

otherFiles := make(map[protocol.DocumentURI]map[string]bool)

addObj := func(obj types.Object) {

if obj == nil {

return

}

pos := obj.Pos()

if !pos.IsValid() {

return

}

objFile := pkg.FileSet().File(pos)

if objFile == nil {

return

}

uri := protocol.URIFromPath(objFile.Name())

if uri == fh.URI() {

return

}

if _, ok := otherFiles[uri]; !ok {

otherFiles[uri] = make(map[string]bool)

}

otherFiles[uri][obj.Name()] = true

}

for cur := range pgf.Cursor.Preorder((*ast.Ident)(nil)) {

id := cur.Node().(*ast.Ident)

addObj(info.Uses[id])

addObj(info.Defs[id])

}

var result strings.Builder

fmt.Fprintf(&result, "File `%s` is in package %q.\n", params.Arguments.File, pkg.Metadata().PkgPath)

fmt.Fprintf(&result, "Below is a summary of the APIs it uses from other files.\n")

fmt.Fprintf(&result, "To read the full API of any package, use go_package_api.\n")

for uri, decls := range otherFiles {

pkgPath := "UNKNOWN"

md, err := snapshot.NarrowestMetadataForFile(ctx, uri)

if err != nil {

if ctx.Err() != nil {

return nil, ctx.Err()

}

} else {

pkgPath = string(md.PkgPath)

}

fmt.Fprintf(&result, "Referenced declarations from %s (package %q):\n", uri.Path(), pkgPath)

result.WriteString("```go\n")

if err := writeFileSummary(ctx, snapshot, uri, &result, false, decls); err != nil {

return nil, err

}

result.WriteString("```\n\n")

}

return textResult(result.String()), nil

}

These instructions describe how to efficiently work in the Go programming language using the gopls MCP server. You can load this file directly into a session where the gopls MCP server is connected.

At the start of every session, you MUST use the `go_workspace` tool to learn about the Go workspace. The rest of these instructions apply whenever that tool indicates that the user is in a Go workspace.

These guidelines MUST be followed whenever working in a Go workspace. There are two workflows described below: the 'Read Workflow' must be followed when the user asks a question about a Go workspace. The 'Edit Workflow' must be followed when the user edits a Go workspace.

You may re-do parts of each workflow as necessary to recover from errors. However, you must not skip any steps.

The goal of the read workflow is to understand the codebase.

1. **Understand the workspace layout**: Start by using `go_workspace` to understand the overall structure of the workspace, such as whether it's a module, a workspace, or a GOPATH project.

2. **Find relevant symbols**: If you're looking for a specific type, function, or variable, use `go_search`. This is a fuzzy search that will help you locate symbols even if you don't know the exact name or location.

EXAMPLE: search for the 'Server' type: `go_search({"query":"server"})`

3. **Understand a file and its intra-package dependencies**: When you have a file path and want to understand its contents and how it connects to other files *in the same package*, use `go_file_context`. This tool will show you a summary of the declarations from other files in the same package that are used by the current file. `go_file_context` MUST be used immediately after reading any Go file for the first time, and MAY be re-used if dependencies have changed.

EXAMPLE: to understand `server.go`'s dependencies on other files in its package: `go_file_context({"file":"/path/to/server.go"})`

4. **Understand a package's public API**: When you need to understand what a package provides to external code (i.e., its public API), use `go_package_api`. This is especially useful for understanding third-party dependencies or other packages in the same monorepo.

EXAMPLE: to see the API of the `storage` package: `go_package_api({"packagePaths":["example.com/internal/storage"]})`

The editing workflow is iterative. You should cycle through these steps until the task is complete.

1. **Read first**: Before making any edits, follow the Read Workflow to understand the user's request and the relevant code.

2. **Find references**: Before modifying the definition of any exported symbol, use the `go_symbol_references` tool to find all references to that identifier. This is critical for understanding the impact of your change. Read the files containing references to evaluate if any further edits are required.

EXAMPLE: `go_symbol_references({"file":"/path/to/server.go","symbol":"Server.Run"})`

3. **Make edits**: Make the primary edit, as well as any edits to references you identified in the previous step.

4. **Check for errors**: After every code modification, you MUST call the `go_diagnostics` tool. Pass the paths of the files you have edited. This tool will report any build or analysis errors.

EXAMPLE: `go_diagnostics({"files":["/path/to/server.go"]})`

5. **Fix errors**: If `go_diagnostics` reports any errors, fix them. The tool may provide suggested quick fixes in the form of diffs. You should review these diffs and apply them if they are correct. Once you've applied a fix, re-run `go_diagnostics` to confirm that the issue is resolved. It is OK to ignore 'hint' or 'info' diagnostics if they are not relevant to the current task.

6. **Run tests**: Once `go_diagnostics` reports no errors (and ONLY once there are no errors), run the tests for the packages you have changed. You can do this with `go test [packagePath...]`. Don't run `go test ./...` unless the user explicitly requests it, as doing so may slow down the iteration loop.