v2: Module documentation; refactor LoadModule(); new caddy struct tags (#2924)

This commit goes a long way toward making automated documentation of
Caddy config and Caddy modules possible. It's a broad, sweeping change,
but mostly internal. It allows us to automatically generate docs for all
Caddy modules (including future third-party ones) and make them viewable
on a web page; it also doubles as godoc comments.

As such, this commit makes significant progress in migrating the docs
from our temporary wiki page toward our new website which is still under
construction.

With this change, all host modules will use ctx.LoadModule() and pass in
both the struct pointer and the field name as a string. This allows the
reflect package to read the struct tag from that field so that it can
get the necessary information like the module namespace and the inline
key.

This has the nice side-effect of unifying the code and documentation. It
also simplifies module loading, and handles several variations on field
types for raw module fields (i.e. variations on json.RawMessage, such as
arrays and maps).

I also renamed ModuleInfo.Name -> ModuleInfo.ID, to make it clear that
the ID is the "full name" which includes both the module namespace and
the name. This clarity is helpful when describing module hierarchy.

As of this change, Caddy modules are no longer an experimental design.
I think the architecture is good enough to go forward.

4 files changed, 20 insertions, 24 deletions

diff --git a/modules/caddyhttp/caddyauth/basicauth.go b/modules/caddyhttp/caddyauth/basicauth.go
index 6412d36..8aa44f1 100644
--- a/modules/caddyhttp/caddyauth/basicauth.go
+++ b/modules/caddyhttp/caddyauth/basicauth.go
@@ -28,7 +28,7 @@ func init() {
 
 // HTTPBasicAuth facilitates HTTP basic authentication.
 type HTTPBasicAuth struct {
-	HashRaw     json.RawMessage `json:"hash,omitempty"`
+	HashRaw     json.RawMessage `json:"hash,omitempty" caddy:"namespace=http.authentication.hashes inline_key=algorithm"`
 	AccountList []Account       `json:"accounts,omitempty"`
 	Realm       string          `json:"realm,omitempty"`
 
@@ -39,8 +39,8 @@ type HTTPBasicAuth struct {
 // CaddyModule returns the Caddy module information.
 func (HTTPBasicAuth) CaddyModule() caddy.ModuleInfo {
 	return caddy.ModuleInfo{
-		Name: "http.handlers.authentication.providers.http_basic",
-		New:  func() caddy.Module { return new(HTTPBasicAuth) },
+		ID:  "http.authentication.providers.http_basic",
+		New: func() caddy.Module { return new(HTTPBasicAuth) },
 	}
 }
 
@@ -51,12 +51,11 @@ func (hba *HTTPBasicAuth) Provision(ctx caddy.Context) error {
 	}
 
 	// load password hasher
-	hashIface, err := ctx.LoadModuleInline("algorithm", "http.handlers.authentication.hashes", hba.HashRaw)
+	hasherIface, err := ctx.LoadModule(hba, "HashRaw")
 	if err != nil {
 		return fmt.Errorf("loading password hasher module: %v", err)
 	}
-	hba.Hash = hashIface.(Comparer)
-	hba.HashRaw = nil // allow GC to deallocate
+	hba.Hash = hasherIface.(Comparer)
 
 	if hba.Hash == nil {
 		return fmt.Errorf("hash is required")
diff --git a/modules/caddyhttp/caddyauth/caddyauth.go b/modules/caddyhttp/caddyauth/caddyauth.go
index 48d4fba..c79d080 100644
--- a/modules/caddyhttp/caddyauth/caddyauth.go
+++ b/modules/caddyhttp/caddyauth/caddyauth.go
@@ -15,7 +15,6 @@
 package caddyauth
 
 import (
-	"encoding/json"
 	"fmt"
 	"log"
 	"net/http"
@@ -30,7 +29,7 @@ func init() {
 
 // Authentication is a middleware which provides user authentication.
 type Authentication struct {
-	ProvidersRaw map[string]json.RawMessage `json:"providers,omitempty"`
+	ProvidersRaw caddy.ModuleMap `json:"providers,omitempty" caddy:"namespace=http.authentication.providers"`
 
 	Providers map[string]Authenticator `json:"-"`
 }
@@ -38,23 +37,21 @@ type Authentication struct {
 // CaddyModule returns the Caddy module information.
 func (Authentication) CaddyModule() caddy.ModuleInfo {
 	return caddy.ModuleInfo{
-		Name: "http.handlers.authentication",
-		New:  func() caddy.Module { return new(Authentication) },
+		ID:  "http.handlers.authentication",
+		New: func() caddy.Module { return new(Authentication) },
 	}
 }
 
 // Provision sets up a.
 func (a *Authentication) Provision(ctx caddy.Context) error {
 	a.Providers = make(map[string]Authenticator)
-	for modName, rawMsg := range a.ProvidersRaw {
-		val, err := ctx.LoadModule("http.handlers.authentication.providers."+modName, rawMsg)
-		if err != nil {
-			return fmt.Errorf("loading authentication provider module '%s': %v", modName, err)
-		}
-		a.Providers[modName] = val.(Authenticator)
+	mods, err := ctx.LoadModule(a, "ProvidersRaw")
+	if err != nil {
+		return fmt.Errorf("loading authentication providers: %v", err)
+	}
+	for modName, modIface := range mods.(map[string]interface{}) {
+		a.Providers[modName] = modIface.(Authenticator)
 	}
-	a.ProvidersRaw = nil // allow GC to deallocate
-
 	return nil
 }
 
diff --git a/modules/caddyhttp/caddyauth/caddyfile.go b/modules/caddyhttp/caddyauth/caddyfile.go
index 3600324..8a33e6f 100644
--- a/modules/caddyhttp/caddyauth/caddyfile.go
+++ b/modules/caddyhttp/caddyauth/caddyfile.go
@@ -16,8 +16,8 @@ package caddyauth
 
 import (
 	"encoding/base64"
-	"encoding/json"
 
+	"github.com/caddyserver/caddy/v2"
 	"github.com/caddyserver/caddy/v2/caddyconfig"
 	"github.com/caddyserver/caddy/v2/caddyconfig/httpcaddyfile"
 	"github.com/caddyserver/caddy/v2/modules/caddyhttp"
@@ -97,7 +97,7 @@ func parseCaddyfile(h httpcaddyfile.Helper) (caddyhttp.MiddlewareHandler, error)
 	}
 
 	return Authentication{
-		ProvidersRaw: map[string]json.RawMessage{
+		ProvidersRaw: caddy.ModuleMap{
 			"http_basic": caddyconfig.JSON(ba, nil),
 		},
 	}, nil
diff --git a/modules/caddyhttp/caddyauth/hashes.go b/modules/caddyhttp/caddyauth/hashes.go
index 13010db..3ca5116 100644
--- a/modules/caddyhttp/caddyauth/hashes.go
+++ b/modules/caddyhttp/caddyauth/hashes.go
@@ -33,8 +33,8 @@ type BcryptHash struct{}
 // CaddyModule returns the Caddy module information.
 func (BcryptHash) CaddyModule() caddy.ModuleInfo {
 	return caddy.ModuleInfo{
-		Name: "http.handlers.authentication.hashes.bcrypt",
-		New:  func() caddy.Module { return new(BcryptHash) },
+		ID:  "http.authentication.hashes.bcrypt",
+		New: func() caddy.Module { return new(BcryptHash) },
 	}
 }
 
@@ -61,8 +61,8 @@ type ScryptHash struct {
 // CaddyModule returns the Caddy module information.
 func (ScryptHash) CaddyModule() caddy.ModuleInfo {
 	return caddy.ModuleInfo{
-		Name: "http.handlers.authentication.hashes.scrypt",
-		New:  func() caddy.Module { return new(ScryptHash) },
+		ID:  "http.authentication.hashes.scrypt",
+		New: func() caddy.Module { return new(ScryptHash) },
 	}
 }