checkers: add ruleguard checker (#907)

This is part of the ruleguard integration experiment.

Hopefully, we can get some feedback to improve the way it's integrated.

The simplest way to try it out:
	gocritic check -enable ruleguard -@ruleguard.rules <gorules> <target>

Where:
	<gorules> is a path to a Go rules file
	<target> is a linting target

An example gorules file can be found here:
	https://github.com/quasilyte/go-ruleguard/blob/master/rules.go

Visit https://github.com/quasilyte/go-ruleguard for more info on the ruleguard.

Updates #873
Updates #869
Updates #837
Updates #836
Updates #831

Signed-off-by: Iskander Sharipov <quasilyte@gmail.com>

checkers/ruleguard_checker.go

@@ -0,0 +1,95 @@
+package checkers
+
+import (
+	"bytes"
+	"go/ast"
+	"go/token"
+	"io/ioutil"
+	"log"
+
+	"github.com/go-lintpack/lintpack"
+	"github.com/quasilyte/go-ruleguard/ruleguard"
+)
+
+func init() {
+	var info lintpack.CheckerInfo
+	info.Name = "ruleguard"
+	info.Tags = []string{"style", "experimental"}
+	info.Params = lintpack.CheckerParams{
+		"rules": {
+			Value: "",
+			Usage: "path to a gorules file",
+		},
+	}
+	info.Summary = "Runs user-defined rules using ruleguard linter"
+	info.Details = "Reads a rules file and turns them into go-critic checkers."
+	info.Before = `N/A`
+	info.After = `N/A`
+	info.Note = "See https://github.com/quasilyte/go-ruleguard."
+
+	collection.AddChecker(&info, func(ctx *lintpack.CheckerContext) lintpack.FileWalker {
+		return newRuleguardChecker(&info, ctx)
+	})
+}
+
+func newRuleguardChecker(info *lintpack.CheckerInfo, ctx *lintpack.CheckerContext) *ruleguardChecker {
+	c := &ruleguardChecker{ctx: ctx}
+	rulesFilename := info.Params.String("rules")
+	if rulesFilename == "" {
+		return c
+	}
+
+	// TODO(quasilyte): handle initialization errors better when we make
+	// a transition to the go/analysis framework.
+	//
+	// For now, we log error messages and return a ruleguard checker
+	// with an empty rules set.
+
+	data, err := ioutil.ReadFile(rulesFilename)
+	if err != nil {
+		log.Printf("ruleguard init error: %+v", err)
+		return c
+	}
+
+	fset := token.NewFileSet()
+	rset, err := ruleguard.ParseRules(rulesFilename, fset, bytes.NewReader(data))
+	if err != nil {
+		log.Printf("ruleguard init error: %+v", err)
+		return c
+	}
+
+	c.rset = rset
+	return c
+}
+
+type ruleguardChecker struct {
+	ctx *lintpack.CheckerContext
+
+	rset *ruleguard.GoRuleSet
+}
+
+func (c *ruleguardChecker) WalkFile(f *ast.File) {
+	if c.rset == nil {
+		return
+	}
+
+	ctx := &ruleguard.Context{
+		Pkg:   c.ctx.Pkg,
+		Types: c.ctx.TypesInfo,
+		Sizes: c.ctx.SizesInfo,
+		Fset:  c.ctx.FileSet,
+		Report: func(n ast.Node, msg string, _ *ruleguard.Suggestion) {
+			// TODO(quasilyte): investigate whether we should add a rule name as
+			// a message prefix here.
+			c.ctx.Warn(n, msg)
+		},
+	}
+
+	err := ruleguard.RunRules(ctx, f, c.rset)
+	if err != nil {
+		// Normally this should never happen, but since
+		// we don't have a better mechanism to report errors,
+		// emit a warning.
+		c.ctx.Warn(f, "execution error: %v", err)
+	}
+}

checkers/testdata/_integration/ruleguard/f1.go

@@ -0,0 +1,10 @@
+package foo
+
+import "fmt"
+
+type myError error
+
+func _() {
+	var s1, s2 string
+	var _ = fmt.Sprintf("%s%s", s1, s2)
+}

checkers/testdata/_integration/ruleguard/linttest.golden

@@ -0,0 +1,3 @@
+exit status 1
+./f1.go:5:1: ruleguard: error as an underlying type is probably a mistake
+./f1.go:9:10: ruleguard: suggestion: s1+s2

checkers/testdata/_integration/ruleguard/linttest.params

@@ -0,0 +1 @@
+check -@ruleguard.rules ./rules.go -enable ruleguard ./... | linttest.golden

checkers/testdata/_integration/ruleguard/rules.go

@@ -0,0 +1,15 @@
+// +build ignore
+
+package gorules
+
+import "github.com/quasilyte/go-ruleguard/dsl/fluent"
+
+func _(m fluent.Matcher) {
+	m.Match(`type $x error`).
+		Report(`error as an underlying type is probably a mistake`).
+		Suggest(`type $x struct { error }`)
+
+	m.Match(`fmt.Sprintf("%s%s", $a, $b)`).
+		Where(m["a"].Type.Is(`string`) && m["b"].Type.Is(`string`)).
+		Suggest(`$a+$b`)
+}

go.mod

@@ -14,5 +14,6 @@ require (
 	github.com/mattn/goveralls v0.0.2
 	github.com/pborman/uuid v1.2.0 // indirect
 	github.com/quasilyte/go-consistent v0.0.0-20190521200055-c6f3937de18c
+	github.com/quasilyte/go-ruleguard v0.1.2-0.20200318202121-b00d7a75d3d8
 	golang.org/x/tools v0.0.0-20190521203540-521d6ed310dd
 )

go.sum

@@ -35,6 +35,12 @@ github.com/pborman/uuid v1.2.0 h1:J7Q5mO4ysT1dv8hyrUGHb9+ooztCXu1D8MY8DZYsu3g=
 github.com/pborman/uuid v1.2.0/go.mod h1:X/NO0urCmaxf9VXbdlT7C2Yzkj2IKimNn4k+gtPdI/k=
 github.com/quasilyte/go-consistent v0.0.0-20190521200055-c6f3937de18c h1:JoUA0uz9U0FVFq5p4LjEq4C0VgQ0El320s3Ms0V4eww=
 github.com/quasilyte/go-consistent v0.0.0-20190521200055-c6f3937de18c/go.mod h1:5STLWrekHfjyYwxBRVRXNOSewLJ3PWfDJd1VyTS21fI=
+github.com/quasilyte/go-ruleguard v0.1.1 h1:L+vAaUaPT/iI7p6vl1691zTC5EAAOZE+Fous1k6e9IE=
+github.com/quasilyte/go-ruleguard v0.1.1/go.mod h1:CGFX09Ci3pq9QZdj86B+VGIdNj4VyCo2iPOGS9esB/k=
+github.com/quasilyte/go-ruleguard v0.1.2-0.20200318181856-dc8aae974065 h1:JViY6/0dUURSKOyIRZZo1wSn5fbQzB8Y4uSIrV8gIT0=
+github.com/quasilyte/go-ruleguard v0.1.2-0.20200318181856-dc8aae974065/go.mod h1:CGFX09Ci3pq9QZdj86B+VGIdNj4VyCo2iPOGS9esB/k=
+github.com/quasilyte/go-ruleguard v0.1.2-0.20200318202121-b00d7a75d3d8 h1:DvnesvLtRPQOvaUbfXfh0tpMHg29by0H7F2U+QIkSu8=
+github.com/quasilyte/go-ruleguard v0.1.2-0.20200318202121-b00d7a75d3d8/go.mod h1:CGFX09Ci3pq9QZdj86B+VGIdNj4VyCo2iPOGS9esB/k=
 golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
 golang.org/x/net v0.0.0-20190311183353-d8887717615a/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
 golang.org/x/sync v0.0.0-20190423024810-112230192c58/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=