feat: add support for Provide*() (<type>, error) methods on commands

Author: alecthomas

README.md

@@ -5,43 +5,40 @@
 
 [![](https://godoc.org/github.com/alecthomas/kong?status.svg)](http://godoc.org/github.com/alecthomas/kong) [![CircleCI](https://img.shields.io/circleci/project/github/alecthomas/kong.svg)](https://circleci.com/gh/alecthomas/kong) [![Go Report Card](https://goreportcard.com/badge/github.com/alecthomas/kong)](https://goreportcard.com/report/github.com/alecthomas/kong) [![Slack chat](https://img.shields.io/static/v1?logo=slack&style=flat&label=slack&color=green&message=gophers)](https://gophers.slack.com/messages/CN9DS8YF3)
 
-<!-- TOC depthfrom:2 depthto:3 -->
-
-- [Version 1.0.0 Release](#version-100-release)
-- [Introduction](#introduction)
-- [Help](#help)
-  - [Help as a user of a Kong application](#help-as-a-user-of-a-kong-application)
-  - [Defining help in Kong](#defining-help-in-kong)
-- [Command handling](#command-handling)
-  - [Switch on the command string](#switch-on-the-command-string)
-  - [Attach a Run... error method to each command](#attach-a-run-error-method-to-each-command)
-- [Hooks: BeforeReset, BeforeResolve, BeforeApply, AfterApply and the Bind option](#hooks-beforereset-beforeresolve-beforeapply-afterapply-and-the-bind-option)
-- [Flags](#flags)
-- [Commands and sub-commands](#commands-and-sub-commands)
-- [Branching positional arguments](#branching-positional-arguments)
-- [Positional arguments](#positional-arguments)
-- [Slices](#slices)
-- [Maps](#maps)
-- [Pointers](#pointers)
-- [Nested data structure](#nested-data-structure)
-- [Custom named decoders](#custom-named-decoders)
-- [Supported field types](#supported-field-types)
-- [Custom decoders mappers](#custom-decoders-mappers)
-- [Supported tags](#supported-tags)
-- [Plugins](#plugins)
-- [Dynamic Commands](#dynamic-commands)
-- [Variable interpolation](#variable-interpolation)
-- [Validation](#validation)
-- [Modifying Kong's behaviour](#modifying-kongs-behaviour)
-  - [Namehelp and Descriptionhelp - set the application name description](#namehelp-and-descriptionhelp---set-the-application-name-description)
-  - [Configurationloader, paths... - load defaults from configuration files](#configurationloader-paths---load-defaults-from-configuration-files)
-  - [Resolver... - support for default values from external sources](#resolver---support-for-default-values-from-external-sources)
-  - [\*Mapper... - customising how the command-line is mapped to Go values](#mapper---customising-how-the-command-line-is-mapped-to-go-values)
-  - [ConfigureHelpHelpOptions and HelpHelpFunc - customising help](#configurehelphelpoptions-and-helphelpfunc---customising-help)
-  - [Bind... - bind values for callback hooks and Run methods](#bind---bind-values-for-callback-hooks-and-run-methods)
-  - [Other options](#other-options)
-
-<!-- /TOC -->
+- [Kong is a command-line parser for Go](#kong-is-a-command-line-parser-for-go)
+  - [Version 1.0.0 Release](#version-100-release)
+  - [Introduction](#introduction)
+  - [Help](#help)
+    - [Help as a user of a Kong application](#help-as-a-user-of-a-kong-application)
+    - [Defining help in Kong](#defining-help-in-kong)
+  - [Command handling](#command-handling)
+    - [Switch on the command string](#switch-on-the-command-string)
+    - [Attach a `Run(...) error` method to each command](#attach-a-run-error-method-to-each-command)
+  - [Hooks: BeforeReset(), BeforeResolve(), BeforeApply(), AfterApply() and the Bind() option](#hooks-beforereset-beforeresolve-beforeapply-afterapply-and-the-bind-option)
+  - [Flags](#flags)
+  - [Commands and sub-commands](#commands-and-sub-commands)
+  - [Branching positional arguments](#branching-positional-arguments)
+  - [Positional arguments](#positional-arguments)
+  - [Slices](#slices)
+  - [Maps](#maps)
+  - [Pointers](#pointers)
+  - [Nested data structure](#nested-data-structure)
+  - [Custom named decoders](#custom-named-decoders)
+  - [Supported field types](#supported-field-types)
+  - [Custom decoders (mappers)](#custom-decoders-mappers)
+  - [Supported tags](#supported-tags)
+  - [Plugins](#plugins)
+  - [Dynamic Commands](#dynamic-commands)
+  - [Variable interpolation](#variable-interpolation)
+  - [Validation](#validation)
+  - [Modifying Kong's behaviour](#modifying-kongs-behaviour)
+    - [`Name(help)` and `Description(help)` - set the application name description](#namehelp-and-descriptionhelp---set-the-application-name-description)
+    - [`Configuration(loader, paths...)` - load defaults from configuration files](#configurationloader-paths---load-defaults-from-configuration-files)
+    - [`Resolver(...)` - support for default values from external sources](#resolver---support-for-default-values-from-external-sources)
+    - [`*Mapper(...)` - customising how the command-line is mapped to Go values](#mapper---customising-how-the-command-line-is-mapped-to-go-values)
+    - [`ConfigureHelp(HelpOptions)` and `Help(HelpFunc)` - customising help](#configurehelphelpoptions-and-helphelpfunc---customising-help)
+    - [`Bind(...)` - bind values for callback hooks and Run() methods](#bind---bind-values-for-callback-hooks-and-run-methods)
+    - [Other options](#other-options)
 
 ## Version 1.0.0 Release
 
@@ -755,9 +752,14 @@ The default help output is usually sufficient, but if not there are two solution
 3. Use `ValueFormatter(HelpValueFormatter)` if you want to just customize the help text that is accompanied by flags and arguments.
 4. Use `Groups([]Group)` if you want to customize group titles or add a header.
 
-### `Bind(...)` - bind values for callback hooks and Run() methods
+### Injecting values into `Run()` methods
 
-See the [section on hooks](#hooks-beforereset-beforeresolve-beforeapply-afterapply-and-the-bind-option) for details.
+There are several ways to inject values into `Run()` methods:
+
+1. Use `Bind()` to bind values directly.
+2. Use `BindTo()` to bind values to an interface type.
+3. Use `BindToProvider()` to bind values to a function that provides the value.
+4. Implement `Provide<Type>() error` methods on the command structure.
 
 ### Other options
 

context.go

@@ -782,6 +782,19 @@ func (c *Context) RunNode(node *Node, binds ...interface{}) (err error) {
 		methodBinds = methodBinds.clone()
 		for p := node; p != nil; p = p.Parent {
 			methodBinds = methodBinds.add(p.Target.Addr().Interface())
+			// Try value and pointer to value.
+			for _, p := range []reflect.Value{p.Target, p.Target.Addr()} {
+				t := p.Type()
+				for i := 0; i < p.NumMethod(); i++ {
+					methodt := t.Method(i)
+					if strings.HasPrefix(methodt.Name, "Provide") {
+						method := p.Method(i)
+						if err := methodBinds.addProvider(method.Interface()); err != nil {
+							return fmt.Errorf("%s.%s: %w", t.Name(), methodt.Name, err)
+						}
+					}
+				}
+			}
 		}
 		if method.IsValid() {
 			methods = append(methods, targetMethod{node, method, methodBinds})

kong_test.go

@@ -2381,3 +2381,28 @@ func TestAfterRun(t *testing.T) {
 	assert.NoError(t, err)
 	assert.Equal(t, afterRunCLI{runCalled: true, afterRunCalled: true}, cli)
 }
+
+type ProvidedString string
+
+type providerCLI struct {
+	Sub providerSubCommand `cmd:""`
+}
+
+type providerSubCommand struct{}
+
+func (p *providerCLI) ProvideFoo() (ProvidedString, error) {
+	return ProvidedString("foo"), nil
+}
+
+func (p *providerSubCommand) Run(t *testing.T, ps ProvidedString) error {
+	assert.Equal(t, ProvidedString("foo"), ps)
+	return nil
+}
+
+func TestProviderMethods(t *testing.T) {
+	k := mustNew(t, &providerCLI{})
+	kctx, err := k.Parse([]string{"sub"})
+	assert.NoError(t, err)
+	err = kctx.Run(t)
+	assert.NoError(t, err)
+}