Go plugin system

.golangci.example.yml

@@ -230,6 +230,18 @@ linters-settings:
     # Force newlines in end of case at this limit (0 = never).
     force-case-trailing-whitespace: 0
 
+  # The custom section can be used to define linter plugins to be loaded at runtime. See README doc
+  #  for more info.
+  custom:
+    # Each custom linter should have a unique name.
+     example:
+      # The path to the plugin *.so. Can be absolute or local. Required for each custom linter
+      path: /path/to/example.so
+      # The description of the linter. Optional, just for documentation purposes.
+      description: This is an example usage of a plugin linter.
+      # Intended to point to the repo location of the linter. Optional, just for documentation purposes.
+      original-url: github.com/golangci/example-linter
+
 linters:
   enable:
     - megacheck

Makefile

@@ -108,4 +108,8 @@ go.sum: go.mod
 
 vendor: go.mod go.sum
 	go mod vendor
-.PHONY: vendor
+
+unexport GOFLAGS
+vendor_free_build: FORCE
+	go build -o golangci-lint ./cmd/golangci-lint
+.PHONY: vendor_free_build vendor

README.md

@@ -834,6 +834,18 @@ linters-settings:
     # Force newlines in end of case at this limit (0 = never).
     force-case-trailing-whitespace: 0
 
+  # The custom section can be used to define linter plugins to be loaded at runtime. See README doc
+  #  for more info.
+  custom:
+    # Each custom linter should have a unique name.
+     example:
+      # The path to the plugin *.so. Can be absolute or local. Required for each custom linter
+      path: /path/to/example.so
+      # The description of the linter. Optional, just for documentation purposes.
+      description: This is an example usage of a plugin linter.
+      # Intended to point to the repo location of the linter. Optional, just for documentation purposes.
+      original-url: github.com/golangci/example-linter
+
 linters:
   enable:
     - megacheck
@@ -1026,6 +1038,58 @@ service:
     - echo "here I can run custom commands, but no preparation needed for this repo"
 ```
 
+## Custom Linters
+Some people and organizations may choose to have custom made linters run as a part of golangci-lint. That functionality 
+is supported through go's plugin library.
+
+### Create a Copy of `golangci-lint` that Can Run with Plugins
+In order to use plugins, you'll need a golangci-lint executable that can run them. The normal version of this project 
+is built with the vendors option, which breaks plugins that have overlapping dependencies.
+
+1. Download [golangci-lint](https://github.com/golangci/golangci-lint) source code
+2. From the projects root directory, run `make vendor_free_build`
+3. Copy the `golangci-lint` executable that was created to your path, project, or other location
+
+### Configure Your Project for Linting
+If you already have a linter plugin available, you can follow these steps to define it's usage in a projects 
+`.golangci.yml` file. An example linter can be found at [here](https://github.com/golangci/example-plugin-linter). If you're looking for 
+instructions on how to configure your own custom linter, they can be found further down.
+
+1. If the project you want to lint does not have one already, copy the [.golangci.yml](https://github.com/golangci/golangci-lint/blob/master/.golangci.yml) to the root directory.
+2. Adjust the yaml to appropriate `linters-settings:custom` entries as so:
+```
+linters-settings:
+ custom:
+  example:
+   path: /example.so
+   description: The description of the linter
+   original-url: github.com/golangci/example-linter
+```
+
+That is all the configuration that is required to run a custom linter in your project. Custom linters are enabled by default,
+but abide by the same rules as other linters. If the disable all option is specified either on command line or in 
+`.golang.yml` files `linters:disable-all: true`, custom linters will be disabled; they can be re-enabled by adding them 
+to the `linters:enable` list, or providing the enabled option on the command line, `golangci-lint run -Eexample`.
+
+### To Create Your Own Custom Linter
+
+Your linter must implement one or more `golang.org/x/tools/go/analysis.Analyzer` structs.
+Your project should also use `go.mod`. All versions of libraries that overlap `golangci-lint` (including replaced 
+libraries) MUST be set to the same version as `golangci-lint`. You can see the versions by running `go version -m golangci-lint`.
+
+You'll also need to create a go file like `plugin/example.go`. This MUST be in the package `main`, and define a 
+variable of name `AnalyzerPlugin`. The `AnalyzerPlugin` instance MUST implement the following interface:
+```
+type AnalyzerPlugin interface {
+    GetAnalyzers() []*analysis.Analyzer
+}
+```
+The type of `AnalyzerPlugin` is not important, but is by convention `type analyzerPlugin struct {}`. See 
+[plugin/example.go](https://github.com/golangci/example-plugin-linter/plugin/example.go) for more info.
+
+To build the plugin, from the root project directory, run `go build -buildmode=plugin plugin/example.go`. This will create a plugin `*.so`
+file that can be copied into your project or another well known location for usage in golangci-lint.
+
 ## False Positives
 
 False positives are inevitable, but we did our best to reduce their count. For example, we have a default enabled set of [exclude patterns](#command-line-options). If a false positive occurred you have the following choices:

README.tmpl.md

@@ -455,6 +455,58 @@ than the default and have more strict settings:
 {{.GolangciYaml}}
 ```
 
+## Custom Linters
+Some people and organizations may choose to have custom made linters run as a part of golangci-lint. That functionality 
+is supported through go's plugin library.
+
+### Create a Copy of `golangci-lint` that Can Run with Plugins
+In order to use plugins, you'll need a golangci-lint executable that can run them. The normal version of this project 
+is built with the vendors option, which breaks plugins that have overlapping dependencies.
+
+1. Download [golangci-lint](https://github.com/golangci/golangci-lint) source code
+2. From the projects root directory, run `make vendor_free_build`
+3. Copy the `golangci-lint` executable that was created to your path, project, or other location
+
+### Configure Your Project for Linting
+If you already have a linter plugin available, you can follow these steps to define it's usage in a projects 
+`.golangci.yml` file. An example linter can be found at [here](https://github.com/golangci/example-plugin-linter). If you're looking for 
+instructions on how to configure your own custom linter, they can be found further down.
+
+1. If the project you want to lint does not have one already, copy the [.golangci.yml](https://github.com/golangci/golangci-lint/blob/master/.golangci.yml) to the root directory.
+2. Adjust the yaml to appropriate `linters-settings:custom` entries as so:
+```
+linters-settings:
+ custom:
+  example:
+   path: /example.so
+   description: The description of the linter
+   original-url: github.com/golangci/example-linter
+```
+
+That is all the configuration that is required to run a custom linter in your project. Custom linters are enabled by default,
+but abide by the same rules as other linters. If the disable all option is specified either on command line or in 
+`.golang.yml` files `linters:disable-all: true`, custom linters will be disabled; they can be re-enabled by adding them 
+to the `linters:enable` list, or providing the enabled option on the command line, `golangci-lint run -Eexample`.
+
+### To Create Your Own Custom Linter
+
+Your linter must implement one or more `golang.org/x/tools/go/analysis.Analyzer` structs.
+Your project should also use `go.mod`. All versions of libraries that overlap `golangci-lint` (including replaced 
+libraries) MUST be set to the same version as `golangci-lint`. You can see the versions by running `go version -m golangci-lint`.
+
+You'll also need to create a go file like `plugin/example.go`. This MUST be in the package `main`, and define a 
+variable of name `AnalyzerPlugin`. The `AnalyzerPlugin` instance MUST implement the following interface:
+```
+type AnalyzerPlugin interface {
+    GetAnalyzers() []*analysis.Analyzer
+}
+```
+The type of `AnalyzerPlugin` is not important, but is by convention `type analyzerPlugin struct {}`. See 
+[plugin/example.go](https://github.com/golangci/example-plugin-linter/plugin/example.go) for more info.
+
+To build the plugin, from the root project directory, run `go build -buildmode=plugin plugin/example.go`. This will create a plugin `*.so`
+file that can be copied into your project or another well known location for usage in golangci-lint.
+
 ## False Positives
 
 False positives are inevitable, but we did our best to reduce their count. For example, we have a default enabled set of [exclude patterns](#command-line-options). If a false positive occurred you have the following choices:

pkg/commands/executor.go

@@ -60,7 +60,7 @@ func NewExecutor(version, commit, date string) *Executor {
 		version:   version,
 		commit:    commit,
 		date:      date,
-		DBManager: lintersdb.NewManager(nil),
+		DBManager: lintersdb.NewManager(nil, nil),
 		debugf:    logutils.Debug("exec"),
 	}
 
@@ -112,7 +112,7 @@ func NewExecutor(version, commit, date string) *Executor {
 	}
 
 	// recreate after getting config
-	e.DBManager = lintersdb.NewManager(e.cfg)
+	e.DBManager = lintersdb.NewManager(e.cfg, e.log).WithCustomLinters()
 
 	e.cfg.LintersSettings.Gocritic.InferEnabledChecks(e.log)
 	if err = e.cfg.LintersSettings.Gocritic.Validate(e.log); err != nil {

pkg/config/config.go

@@ -190,6 +190,8 @@ type LintersSettings struct {
 	Godox    GodoxSettings
 	Dogsled  DogsledSettings
 	Gocognit GocognitSettings
+
+	Custom map[string]CustomLinterSettings
 }
 
 type GovetSettings struct {
@@ -301,6 +303,12 @@ var defaultLintersSettings = LintersSettings{
 	},
 }
 
+type CustomLinterSettings struct {
+	Path        string
+	Description string
+	OriginalURL string `mapstructure:"original-url"`
+}
+
 type Linters struct {
 	Enable     []string
 	Disable    []string

pkg/lint/lintersdb/enabled_set_test.go

@@ -91,7 +91,7 @@ func TestGetEnabledLintersSet(t *testing.T) {
 		},
 	}
 
-	m := NewManager(nil)
+	m := NewManager(nil, nil)
 	es := NewEnabledSet(m, NewValidator(m), nil, nil)
 	for _, c := range cases {
 		c := c

pkg/lint/lintersdb/manager.go

@@ -1,20 +1,28 @@
 package lintersdb
 
 import (
+	"fmt"
 	"os"
+	"plugin"
+
+	"golang.org/x/tools/go/analysis"
 
 	"github.com/golangci/golangci-lint/pkg/config"
 	"github.com/golangci/golangci-lint/pkg/golinters"
+	"github.com/golangci/golangci-lint/pkg/golinters/goanalysis"
 	"github.com/golangci/golangci-lint/pkg/lint/linter"
+	"github.com/golangci/golangci-lint/pkg/logutils"
+	"github.com/golangci/golangci-lint/pkg/report"
 )
 
 type Manager struct {
 	nameToLCs map[string][]*linter.Config
 	cfg       *config.Config
+	log       logutils.Log
 }
 
-func NewManager(cfg *config.Config) *Manager {
-	m := &Manager{cfg: cfg}
+func NewManager(cfg *config.Config, log logutils.Log) *Manager {
+	m := &Manager{cfg: cfg, log: log}
 	nameToLCs := make(map[string][]*linter.Config)
 	for _, lc := range m.GetAllSupportedLinterConfigs() {
 		for _, name := range lc.AllNames() {
@@ -26,6 +34,27 @@ func NewManager(cfg *config.Config) *Manager {
 	return m
 }
 
+func (m *Manager) WithCustomLinters() *Manager {
+	if m.log == nil {
+		m.log = report.NewLogWrapper(logutils.NewStderrLog(""), &report.Data{})
+	}
+	if m.cfg != nil {
+		for name, settings := range m.cfg.LintersSettings.Custom {
+			lc, err := m.loadCustomLinterConfig(name, settings)
+
+			if err != nil {
+				m.log.Errorf("Unable to load custom analyzer %s:%s, %v",
+					name,
+					settings.Path,
+					err)
+			} else {
+				m.nameToLCs[name] = append(m.nameToLCs[name], lc)
+			}
+		}
+	}
+	return m
+}
+
 func (Manager) AllPresets() []string {
 	return []string{linter.PresetBugs, linter.PresetComplexity, linter.PresetFormatting,
 		linter.PresetPerformance, linter.PresetStyle, linter.PresetUnused}
@@ -267,3 +296,44 @@ func (m Manager) GetAllLinterConfigsForPreset(p string) []*linter.Config {
 
 	return ret
 }
+
+func (m Manager) loadCustomLinterConfig(name string, settings config.CustomLinterSettings) (*linter.Config, error) {
+	analyzer, err := m.getAnalyzerPlugin(settings.Path)
+	if err != nil {
+		return nil, err
+	}
+	m.log.Infof("Loaded %s: %s", settings.Path, name)
+	customLinter := goanalysis.NewLinter(
+		name,
+		settings.Description,
+		analyzer.GetAnalyzers(),
+		nil).WithLoadMode(goanalysis.LoadModeTypesInfo)
+	linterConfig := linter.NewConfig(customLinter)
+	linterConfig.EnabledByDefault = true
+	linterConfig.IsSlow = false
+	linterConfig.WithURL(settings.OriginalURL)
+	return linterConfig, nil
+}
+
+type AnalyzerPlugin interface {
+	GetAnalyzers() []*analysis.Analyzer
+}
+
+func (m Manager) getAnalyzerPlugin(path string) (AnalyzerPlugin, error) {
+	plug, err := plugin.Open(path)
+	if err != nil {
+		return nil, err
+	}
+
+	symbol, err := plug.Lookup("AnalyzerPlugin")
+	if err != nil {
+		return nil, err
+	}
+
+	analyzerPlugin, ok := symbol.(AnalyzerPlugin)
+	if !ok {
+		return nil, fmt.Errorf("plugin %s does not abide by 'AnalyzerPlugin' interface", path)
+	}
+
+	return analyzerPlugin, nil
+}

pkg/result/processors/nolint_test.go

@@ -31,7 +31,7 @@ func newNolint2FileIssue(line int) result.Issue {
 }
 
 func newTestNolintProcessor(log logutils.Log) *Nolint {
-	return NewNolint(log, lintersdb.NewManager(nil))
+	return NewNolint(log, lintersdb.NewManager(nil, nil))
 }
 
 func getMockLog() *logutils.MockLog {

scripts/gen_readme/main.go

@@ -114,7 +114,7 @@ func buildTemplateContext() (map[string]interface{}, error) {
 
 func getLintersListMarkdown(enabled bool) string {
 	var neededLcs []*linter.Config
-	lcs := lintersdb.NewManager(nil).GetAllSupportedLinterConfigs()
+	lcs := lintersdb.NewManager(nil, nil).GetAllSupportedLinterConfigs()
 	for _, lc := range lcs {
 		if lc.EnabledByDefault == enabled {
 			neededLcs = append(neededLcs, lc)
@@ -139,7 +139,7 @@ func getLintersListMarkdown(enabled bool) string {
 func getThanksList() string {
 	var lines []string
 	addedAuthors := map[string]bool{}
-	for _, lc := range lintersdb.NewManager(nil).GetAllSupportedLinterConfigs() {
+	for _, lc := range lintersdb.NewManager(nil, nil).GetAllSupportedLinterConfigs() {
 		if lc.OriginalURL == "" {
 			continue
 		}

test/enabled_linters_test.go

@@ -21,7 +21,7 @@ func inSlice(s []string, v string) bool {
 }
 
 func getEnabledByDefaultFastLintersExcept(except ...string) []string {
-	m := lintersdb.NewManager(nil)
+	m := lintersdb.NewManager(nil, nil)
 	ebdl := m.GetAllEnabledByDefaultLinters()
 	ret := []string{}
 	for _, lc := range ebdl {
@@ -38,7 +38,7 @@ func getEnabledByDefaultFastLintersExcept(except ...string) []string {
 }
 
 func getAllFastLintersWith(with ...string) []string {
-	linters := lintersdb.NewManager(nil).GetAllSupportedLinterConfigs()
+	linters := lintersdb.NewManager(nil, nil).GetAllSupportedLinterConfigs()
 	ret := append([]string{}, with...)
 	for _, lc := range linters {
 		if lc.IsSlowLinter() {
@@ -51,7 +51,7 @@ func getAllFastLintersWith(with ...string) []string {
 }
 
 func getEnabledByDefaultLinters() []string {
-	ebdl := lintersdb.NewManager(nil).GetAllEnabledByDefaultLinters()
+	ebdl := lintersdb.NewManager(nil, nil).GetAllEnabledByDefaultLinters()
 	ret := []string{}
 	for _, lc := range ebdl {
 		ret = append(ret, lc.Name())
@@ -61,7 +61,7 @@ func getEnabledByDefaultLinters() []string {
 }
 
 func getEnabledByDefaultFastLintersWith(with ...string) []string {
-	ebdl := lintersdb.NewManager(nil).GetAllEnabledByDefaultLinters()
+	ebdl := lintersdb.NewManager(nil, nil).GetAllEnabledByDefaultLinters()
 	ret := append([]string{}, with...)
 	for _, lc := range ebdl {
 		if lc.IsSlowLinter() {