load plugins at \use-plugin time

this doesn't work. golang/go#20481 seems related.

Signed-off-by: Alex Suraci <suraci.alex@gmail.com>

baselit/plugin.go

@@ -9,7 +9,7 @@ import (
 )
 
 func init() {
-	booklit.RegisterPlugin("base", NewPlugin)
+	booklit.RegisterPlugin("github.com/vito/booklit/baselit", NewPlugin)
 }
 
 func NewPlugin(section *booklit.Section) booklit.Plugin {
@@ -22,10 +22,10 @@ type Plugin struct {
 	section *booklit.Section
 }
 
-func (plugin Plugin) UsePlugin(name string) error {
-	pluginFactory, found := booklit.LookupPlugin(name)
-	if !found {
-		return fmt.Errorf("unknown plugin '%s'", name)
+func (plugin Plugin) UsePlugin(importPath string) error {
+	pluginFactory, err := plugin.section.Processor.LoadPlugin(importPath)
+	if err != nil {
+		return err
 	}
 
 	plugin.section.UsePlugin(pluginFactory)

booklitcmd/command.go

@@ -2,12 +2,8 @@ package booklitcmd
 
 import (
 	"fmt"
-	"io/ioutil"
 	"net/http"
 	"os"
-	"os/exec"
-	"path/filepath"
-	"plugin"
 
 	"github.com/sirupsen/logrus"
 	"github.com/vito/booklit"
@@ -29,8 +25,6 @@ type Command struct {
 
 	ServerPort int `long:"serve" short:"s" description:"Start an HTTP server on the given port."`
 
-	Plugins []string `long:"plugin" short:"p" description:"Package to import, providing a plugin."`
-
 	Debug bool `long:"debug" short:"d" description:"Log at debug level."`
 
 	AllowBrokenReferences bool `long:"allow-broken-references" description:"Replace broken references with a bogus tag."`
@@ -50,11 +44,6 @@ func (cmd *Command) Execute(args []string) error {
 		logrus.SetLevel(logrus.DebugLevel)
 	}
 
-	err := cmd.loadPlugins()
-	if err != nil {
-		return err
-	}
-
 	if cmd.ServerPort != 0 {
 		return cmd.Serve()
 	} else {
@@ -159,42 +148,3 @@ func (cmd *Command) Build() error {
 
 	return nil
 }
-
-func (cmd *Command) loadPlugins() error {
-	tmpdir, err := ioutil.TempDir("", "booklit-reexec")
-	if err != nil {
-		return err
-	}
-
-	defer func() {
-		_ = os.RemoveAll(tmpdir)
-	}()
-
-	for i, p := range cmd.Plugins {
-		log := logrus.WithFields(logrus.Fields{
-			"plugin": p,
-		})
-
-		pluginPath := filepath.Join(tmpdir, fmt.Sprintf("plugin-%d.so", i))
-
-		build := exec.Command("go", "build", "-buildmode=plugin", "-o", pluginPath, p)
-		build.Env = append(os.Environ(), "GOBIN="+tmpdir)
-		buildOutput, err := build.CombinedOutput()
-		if err != nil {
-			if _, ok := err.(*exec.ExitError); ok {
-				return fmt.Errorf("failed to compile plugin '%s':\n\n%s", p, string(buildOutput))
-			} else {
-				return err
-			}
-		}
-
-		_, err = plugin.Open(pluginPath)
-		if err != nil {
-			return fmt.Errorf("failed to load plugin '%s': %s", p, err)
-		}
-
-		log.Info("loaded plugin")
-	}
-
-	return nil
-}

booklitdoc/plugin.go

@@ -13,7 +13,7 @@ import (
 )
 
 func init() {
-	booklit.RegisterPlugin("booklitdoc", NewPlugin)
+	booklit.RegisterPlugin("github.com/vito/booklit/booklitdoc", NewPlugin)
 
 	styles.Fallback = chroma.MustNewStyle("booklitdoc", chroma.StyleEntries{
 		chroma.Comment:               "italic",

chroma/plugin/main.go

@@ -6,5 +6,5 @@ import (
 )
 
 func init() {
-	booklit.RegisterPlugin("chroma", chroma.NewPlugin)
+	booklit.RegisterPlugin("github.com/vito/booklit/chroma/plugin", chroma.NewPlugin)
 }

docs/lit/baselit.lit

@@ -1,5 +1,5 @@
-\use-plugin{booklitdoc}
-\use-plugin{chroma}
+\use-plugin{github.com/vito/booklit/booklitdoc}
+\use-plugin{github.com/vito/booklit/chroma/plugin}
 
 \title{The \code{baselit} Plugin}{baselit}
 

docs/lit/getting-started.lit

@@ -1,4 +1,4 @@
-\use-plugin{chroma}
+\use-plugin{github.com/vito/booklit/chroma/plugin}
 
 \title{Getting Started}
 

docs/lit/html-renderer.lit

@@ -1,5 +1,5 @@
-\use-plugin{booklitdoc}
-\use-plugin{chroma}
+\use-plugin{github.com/vito/booklit/booklitdoc}
+\use-plugin{github.com/vito/booklit/chroma/plugin}
 
 \title{The HTML Renderer}{html-renderer}
 

docs/lit/plugins.lit

@@ -1,5 +1,5 @@
-\use-plugin{booklitdoc}
-\use-plugin{chroma}
+\use-plugin{github.com/vito/booklit/booklitdoc}
+\use-plugin{github.com/vito/booklit/chroma/plugin}
 
 \title{Extending with Plugins}{plugins}
 

docs/lit/syntax.lit

@@ -1,4 +1,4 @@
-\use-plugin{chroma}
+\use-plugin{github.com/vito/booklit/chroma/plugin}
 
 \title{Document Syntax}{syntax}
 

load/processor.go

@@ -1,7 +1,12 @@
 package load
 
 import (
+	"fmt"
+	"io/ioutil"
 	"os"
+	"os/exec"
+	"path/filepath"
+	"plugin"
 	"sync"
 	"time"
 
@@ -17,6 +22,9 @@ type Processor struct {
 
 	parsed  map[string]parsedNode
 	parsedL sync.Mutex
+
+	loadedPlugins  map[string]booklit.PluginFactory
+	loadedPluginsL sync.Mutex
 }
 
 type parsedNode struct {
@@ -125,6 +133,56 @@ func (processor *Processor) EvaluateNode(parent *booklit.Section, node ast.Node,
 	return section, nil
 }
 
+func (processor *Processor) LoadPlugin(importPath string) (booklit.PluginFactory, error) {
+	processor.loadedPluginsL.Lock()
+	defer processor.loadedPluginsL.Unlock()
+
+	if processor.loadedPlugins == nil {
+		processor.loadedPlugins = map[string]booklit.PluginFactory{}
+	}
+
+	pf, found := processor.loadedPlugins[importPath]
+	if found {
+		return pf, nil
+	}
+
+	tmpdir, err := ioutil.TempDir("", "booklit-load-plugin")
+	if err != nil {
+		return nil, err
+	}
+
+	defer func() {
+		_ = os.RemoveAll(tmpdir)
+	}()
+
+	pluginPath := filepath.Join(tmpdir, "plugin.so")
+
+	build := exec.Command("go", "build", "-buildmode=plugin", "-o", pluginPath, importPath)
+	build.Env = append(os.Environ(), "GOBIN="+tmpdir)
+	buildOutput, err := build.CombinedOutput()
+	if err != nil {
+		if _, ok := err.(*exec.ExitError); ok {
+			return nil, fmt.Errorf("failed to compile plugin '%s':\n\n%s", importPath, string(buildOutput))
+		} else {
+			return nil, err
+		}
+	}
+
+	_, err = plugin.Open(pluginPath)
+	if err != nil {
+		return nil, fmt.Errorf("failed to open plugin '%s': %s", importPath, err)
+	}
+
+	pf, found = booklit.LookupPlugin(importPath)
+	if !found {
+		return nil, fmt.Errorf("plugin loaded but did not register as '%s'", importPath)
+	}
+
+	processor.loadedPlugins[importPath] = pf
+
+	return pf, nil
+}
+
 func (processor *Processor) evaluateSection(section *booklit.Section, node ast.Node, pluginFactories []booklit.PluginFactory) error {
 	for _, pf := range pluginFactories {
 		section.UsePlugin(pf)

scripts/build-docs

@@ -4,6 +4,4 @@ go run cmd/booklit/*.go \
   -i docs/lit/index.lit \
   -o docs \
   --html-templates docs/lit/html \
-  --plugin github.com/vito/booklit/booklitdoc \
-  --plugin github.com/vito/booklit/chroma/plugin \
   "$@"

section.go

@@ -38,6 +38,7 @@ type Section struct {
 type Partials map[string]Content
 
 type SectionProcessor interface {
+	LoadPlugin(importPath string) (PluginFactory, error)
 	EvaluateFile(*Section, string, []PluginFactory) (*Section, error)
 	EvaluateNode(*Section, ast.Node, []PluginFactory) (*Section, error)
 }