Go plugin system

.golangci.example.yml

@@ -228,6 +228,21 @@ linters-settings:
     # Allow declarations (var) to be cuddled.
     allow-cuddle-declarations: false
 
+  # 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 name. This name should match with what the linter reports for itself.
+     example:
+      # The path to the plugin *.so. Required for each custom linter
+      path: /path/to/example.so
+      # If the linter should be enabled by default. Options in the `linters`
+      #  section override this, including `disable-all`. Optional, false by default.
+      enabled: true
+      # Intended to point to the repo location of the linter. Optional, just for documentation purposes.
+      original-url: github.com/dbraley/example-linter
+      # Indicates if this linter should be considered slow. Optional, false by default.
+      slow: false
+
 linters:
   enable:
     - megacheck

Makefile

@@ -107,3 +107,8 @@ go.sum: go.mod
 .PHONY: vendor
 vendor: go.mod go.sum
 	go mod vendor
+
+unexport GOFLAGS
+vendor_free_build: FORCE
+	go build -o golangci-lint ./cmd/golangci-lint
+.PHONY: vendor_free_build

README.md

@@ -828,6 +828,21 @@ linters-settings:
     # Allow declarations (var) to be cuddled.
     allow-cuddle-declarations: false
 
+  # 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 name. This name should match with what the linter reports for itself.
+     example:
+      # The path to the plugin *.so. Required for each custom linter
+      path: /path/to/example.so
+      # If the linter should be enabled by default. Options in the `linters`
+      #  section override this, including `disable-all`. Optional, false by default.
+      enabled: true
+      # Intended to point to the repo location of the linter. Optional, just for documentation purposes.
+      original-url: github.com/dbraley/example-linter
+      # Indicates if this linter should be considered slow. Optional, false by default.
+      slow: false
+
 linters:
   enable:
     - megacheck
@@ -1027,6 +1042,66 @@ 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 the `i473` branch of https://github.com/dbraley/golangci-lint/tree/i473
+2. From that 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 https://github.com/dbraley/example-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 https://github.com/dbraley/golangci-lint/blob/i473/.golangci.yml to the root directory.
+2. Adjust the yaml to appropriate `linters-settings:custom` entries as so:
+```
+linters-settings:
+ custom:
+  example: # If this doesn't match the linters name definition, it will warn you but still run
+   path: /example.so # Adjust this the location of the plugin
+   enabled: true # This determines if the linter is run by default
+   original-url: github.com/dbraley/example-linter # This is just documentation for custom linters
+   slow: false # Set this to true to observe `--fast` option
+```
+3. If your `.golangci.yml` file has `linters:disable-all` set to true, you'll also need to add your linter to the `linters:enable` seciont:
+```
+linters:
+ enable:
+  # ...
+  - varcheck
+  - whitespace
+  # Custom linters
+  - example
+```
+4. Alternately, you can leave it disabled and turn it on via command line only: `golangci-lint run -Eexample`
+5. If everything works correctly, you should see the linter show up as enabled by running `golangci-lint linters`. This linter will look for `// TODO: ` in front of functions, so you can also add that to your code and see the errors.
+6. You can also see the linter get loaded with the `-v` option for either `run` or `linters`
+
+### To Configure Your Own `golang.org/x/tools/go/analysis` Based Linter
+
+Your Linter must implement one or more `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 want to create a go file like `plugin/example.go`. This MUST be in the package `main`, and define:
+1. A variable of type `analyzerPlugin`. The type `analyzerPlugin` can be defined as a string, struct, whatever.
+```
+type analyzerPlugin struct{}
+var AnalyzerPlugin analyzerPlugin
+```
+2. A function with signature `func (*analyzerPlugin) GetLinterName() string`
+3. A function with signature `func (*analyzerPlugin) GetLinterDesc() string`
+4. A function with signature `func (*analyzerPlugin) GetAnalyzers() []*analysis.Analyzer`
+
+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

@@ -453,6 +453,66 @@ 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 the `i473` branch of https://github.com/dbraley/golangci-lint/tree/i473
+2. From that 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 https://github.com/dbraley/example-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 https://github.com/dbraley/golangci-lint/blob/i473/.golangci.yml to the root directory.
+2. Adjust the yaml to appropriate `linters-settings:custom` entries as so:
+```
+linters-settings:
+ custom:
+  example: # If this doesn't match the linters name definition, it will warn you but still run
+   path: /example.so # Adjust this the location of the plugin
+   enabled: true # This determines if the linter is run by default
+   original-url: github.com/dbraley/example-linter # This is just documentation for custom linters
+   slow: false # Set this to true to observe `--fast` option
+```
+3. If your `.golangci.yml` file has `linters:disable-all` set to true, you'll also need to add your linter to the `linters:enable` seciont:
+```
+linters:
+ enable:
+  # ...
+  - varcheck
+  - whitespace
+  # Custom linters
+  - example
+```
+4. Alternately, you can leave it disabled and turn it on via command line only: `golangci-lint run -Eexample`
+5. If everything works correctly, you should see the linter show up as enabled by running `golangci-lint linters`. This linter will look for `// TODO: ` in front of functions, so you can also add that to your code and see the errors.
+6. You can also see the linter get loaded with the `-v` option for either `run` or `linters`
+
+### To Configure Your Own `golang.org/x/tools/go/analysis` Based Linter
+
+Your Linter must implement one or more `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 want to create a go file like `plugin/example.go`. This MUST be in the package `main`, and define:
+1. A variable of type `analyzerPlugin`. The type `analyzerPlugin` can be defined as a string, struct, whatever.
+```
+type analyzerPlugin struct{}
+var AnalyzerPlugin analyzerPlugin
+```
+2. A function with signature `func (*analyzerPlugin) GetLinterName() string`
+3. A function with signature `func (*analyzerPlugin) GetLinterDesc() string`
+4. A function with signature `func (*analyzerPlugin) GetAnalyzers() []*analysis.Analyzer`
+
+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

@@ -62,7 +62,7 @@ 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"),
 	}
 
@@ -114,7 +114,7 @@ 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 {
@@ -299,6 +301,13 @@ var defaultLintersSettings = LintersSettings{
 	},
 }
 
+type CustomLinterSettings struct {
+	Path        string
+	Enabled     bool
+	OriginalUrl string `mapstructure:"original-url"`
+	Slow        bool
+}
+
 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

@@ -1,7 +1,14 @@
 package lintersdb
 
 import (
+	"fmt"
+	"github.com/golangci/golangci-lint/pkg/golinters/goanalysis"
+	"github.com/golangci/golangci-lint/pkg/logutils"
+	"github.com/golangci/golangci-lint/pkg/report"
+	"github.com/prometheus/common/log"
+	"golang.org/x/tools/go/analysis"
 	"os"
+	"plugin"
 
 	"github.com/golangci/golangci-lint/pkg/config"
 	"github.com/golangci/golangci-lint/pkg/golinters"
@@ -11,10 +18,11 @@ import (
 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 {
+				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}
@@ -264,3 +293,50 @@ 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
+	} else {
+		m.log.Infof("Loaded %s: %s", settings.Path, analyzer.GetLinterName())
+		customLinter := goanalysis.NewLinter(
+			analyzer.GetLinterName(),
+			analyzer.GetLinterDesc(),
+			analyzer.GetAnalyzers(),
+			nil).WithLoadMode(goanalysis.LoadModeTypesInfo)
+		linterConfig := linter.NewConfig(customLinter)
+		linterConfig.EnabledByDefault = settings.Enabled
+		linterConfig.IsSlow = settings.Slow
+		linterConfig.WithURL(settings.OriginalUrl)
+		if name != linterConfig.Name() {
+			m.log.Warnf("Configuration linter name %s doesn't match plugin linter name %s", name, linterConfig.Name())
+		}
+		return linterConfig, nil
+	}
+}
+
+type AnalyzerPlugin interface {
+	GetLinterName() string
+	GetLinterDesc() string
+	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
 		}