Merge pull request cli#13024 from cli/agents-md

Add AGENTS.md

Author: williammartin

AGENTS.md

@@ -0,0 +1,165 @@
+# AGENTS.md
+
+This is the GitHub CLI (`gh`), a command-line tool for interacting with GitHub. The module path is `github.com/cli/cli/v2`.
+
+## Build, Test, and Lint
+
+```bash
+make                                       # Build (Unix) — outputs bin/gh
+go run script/build.go                     # Build (Windows)
+go test ./...                              # All unit tests
+go test ./pkg/cmd/issue/list/... -run TestIssueList_nontty  # Single test
+go test -tags acceptance ./acceptance      # Acceptance tests
+make lint                                  # golangci-lint (same as CI)
+```
+
+## Architecture
+
+Entry point: `cmd/gh/main.go` → `internal/ghcmd.Main()` → `pkg/cmd/root.NewCmdRoot()`.
+
+Key packages:
+- `pkg/cmd/<command>/<subcommand>/` — CLI command implementations
+- `pkg/cmdutil/` — Factory, error types, flag helpers (`NilStringFlag`, `NilBoolFlag`, `StringEnumFlag`)
+- `pkg/iostreams/` — I/O abstraction with TTY detection, color, pager
+- `pkg/httpmock/` — HTTP mocking for tests
+- `api/` — GitHub API client (GraphQL + REST)
+- `internal/featuredetection/` — GitHub.com vs GHES capability detection
+- `internal/tableprinter/` — Table output for list commands
+
+## Command Structure
+
+A command `gh foo bar` lives in `pkg/cmd/foo/bar/` with `bar.go`, `bar_test.go`, and optionally `http.go`/`http_test.go`.
+
+### Canonical Examples
+
+- **Command + tests**: `pkg/cmd/issue/list/list.go` and `list_test.go`
+- **Factory wiring**: `pkg/cmd/factory/default.go`
+- **Unit tests**: `internal/agents/detect_test.go`
+
+### The Options + Factory Pattern
+
+Every command follows this structure (see `pkg/cmd/issue/list/list.go`):
+
+1. `Options` struct with `IO`, `HttpClient`, `Config`, `BaseRepo` + flags
+2. `NewCmdFoo(f *cmdutil.Factory, runF func(*FooOptions) error)` constructor — `runF` is the test injection point
+3. Separate `fooRun(opts)` function with the business logic
+
+Key rules:
+- Lazy-init `BaseRepo`, `Remotes`, `Branch` inside `RunE`, not the constructor
+- Commands register in `pkg/cmd/root/root.go`; subcommand groups use `cmdutil.AddGroup()`
+
+### Command Examples and Help Text
+
+Use `heredoc.Doc` for examples with `#` comment lines and `$ ` command prefixes:
+```go
+Example: heredoc.Doc(`
+    # Do the thing
+    $ gh foo bar --flag value
+`),
+```
+
+### JSON Output
+
+Add `--json`, `--jq`, `--template` flags via `cmdutil.AddJSONFlags(cmd, &opts.Exporter, fieldNames)`. In the run function: `if opts.Exporter != nil { return opts.Exporter.Write(opts.IO, data) }`. See `pkg/cmd/pr/list/list.go`.
+
+## Testing
+
+### HTTP Mocking
+
+Use `httpmock.Registry` with `defer reg.Verify(t)` to ensure all stubs are called:
+
+```go
+reg := &httpmock.Registry{}
+defer reg.Verify(t)
+
+reg.Register(
+    httpmock.REST("GET", "repos/OWNER/REPO"),
+    httpmock.JSONResponse(someData),
+)
+reg.Register(
+    httpmock.GraphQL(`query PullRequestList\b`),
+    httpmock.FileResponse("./fixtures/prList.json"),
+)
+client := &http.Client{Transport: reg}
+```
+
+Common: `REST(method, path)`, `GraphQL(pattern)`, `JSONResponse(body)`, `FileResponse(path)`. See `pkg/httpmock/` for all matchers/responders.
+
+### IOStreams in Tests
+
+```go
+ios, stdin, stdout, stderr := iostreams.Test()
+ios.SetStdoutTTY(true)  // simulate terminal
+```
+
+### Assertions
+
+Use `testify`. Always use `require` (not `assert`) for error checks so the test halts immediately:
+
+```go
+require.NoError(t, err)
+require.Error(t, err)
+assert.Equal(t, "expected", actual)
+```
+
+### Generated Mocks
+
+Interfaces use `moq`: `//go:generate moq -rm -out prompter_mock.go . Prompter`. Run `go generate ./...` after interface changes.
+
+### Table-Driven Tests
+
+Use table-driven tests for functions with multiple input/output scenarios. See `internal/agents/detect_test.go` or `pkg/cmd/issue/list/list_test.go` for examples:
+
+```go
+tests := []struct {
+    name      string
+    // inputs and expected outputs
+}{
+    {name: "descriptive case name", ...},
+}
+for _, tt := range tests {
+    t.Run(tt.name, func(t *testing.T) {
+        // arrange, act, assert
+    })
+}
+```
+
+## Code Style
+
+- Add godoc comments to all exported functions, types, and constants
+- Avoid unnecessary code comments — only comment when the *why* isn't obvious from the code
+- Do not comment just to restate what the code does
+
+## Error Handling
+
+Error types in `pkg/cmdutil/errors.go`:
+- `FlagErrorf(...)` — flag validation (prints usage)
+- `cmdutil.SilentError` — exit 1, no message
+- `cmdutil.CancelError` — user cancelled
+- `cmdutil.PendingError` — outcome pending
+- `cmdutil.NoResultsError` — empty results
+
+Use `cmdutil.MutuallyExclusive("message", cond1, cond2)` for mutually exclusive flags.
+
+## Feature Detection
+
+Commands using feature detection must include a `// TODO <cleanupIdentifier>` comment directly above the if-statement for linter compliance:
+
+```go
+// TODO someFeatureCleanup
+if features.SomeCapability {
+    // use new API
+} else {
+    // fallback for older GHES
+}
+```
+
+## API Patterns
+
+```go
+client := api.NewClientFromHTTP(httpClient)
+client.GraphQL(hostname, query, variables, &data)
+client.REST(hostname, "GET", "repos/owner/repo", nil, &data)
+```
+
+For host resolution, use `cfg.Authentication().DefaultHost()` — not `ghinstance.Default()` which always returns `github.com`.