Add an option for Go build tags (#201)

* Add an option for Go build tags

* Update README with a section for Go build tags

README.md

@@ -103,6 +103,14 @@ can do the following:
 ```
 $ gas -nosec=true ./...
 ```
+#### Build tags
+
+Gas is able to pass your [Go build tags](https://golang.org/pkg/go/build/) to the analyzer.
+They can be provided as a comma separated list as follows:
+
+```
+$ gas -tag debug,ignore ./...
+```
 
 ### Output formats
 

analyzer.go

@@ -97,9 +97,11 @@ func (gas *Analyzer) LoadRules(ruleDefinitions map[string]RuleBuilder) {
 }
 
 // Process kicks off the analysis process for a given package
-func (gas *Analyzer) Process(packagePaths ...string) error {
+func (gas *Analyzer) Process(buildTags []string, packagePaths ...string) error {
+	ctx := build.Default
+	ctx.BuildTags = append(ctx.BuildTags, buildTags...)
 	packageConfig := loader.Config{
-		Build:       &build.Default,
+		Build:       &ctx,
 		ParserMode:  parser.ParseComments,
 		AllowErrors: true,
 	}

analyzer_test.go

@@ -19,6 +19,7 @@ var _ = Describe("Analyzer", func() {
 	var (
 		analyzer  *gas.Analyzer
 		logger    *log.Logger
+		buildTags []string
 	)
 	BeforeEach(func() {
 		logger, _ = testutils.NewLogger()
@@ -32,7 +33,7 @@ var _ = Describe("Analyzer", func() {
 			dir, err := ioutil.TempDir("", "empty")
 			defer os.RemoveAll(dir)
 			Expect(err).ShouldNot(HaveOccurred())
-			err = analyzer.Process(dir)
+			err = analyzer.Process(buildTags, dir)
 			Expect(err).Should(HaveOccurred())
 			Expect(err.Error()).Should(MatchRegexp("no buildable Go source files"))
 		})
@@ -44,7 +45,7 @@ var _ = Describe("Analyzer", func() {
 			pkg.AddFile("wonky.go", `func main(){ println("forgot the package")}`)
 			pkg.Build()
 
-			err := analyzer.Process(pkg.Path)
+			err := analyzer.Process(buildTags, pkg.Path)
 			Expect(err).Should(HaveOccurred())
 			Expect(err.Error()).Should(MatchRegexp(`expected 'package'`))
 
@@ -65,7 +66,7 @@ var _ = Describe("Analyzer", func() {
 					println("package has two files!")
 				}`)
 			pkg.Build()
-			err := analyzer.Process(pkg.Path)
+			err := analyzer.Process(buildTags, pkg.Path)
 			Expect(err).ShouldNot(HaveOccurred())
 			_, metrics := analyzer.Report()
 			Expect(metrics.NumFiles).To(Equal(2))
@@ -87,7 +88,7 @@ var _ = Describe("Analyzer", func() {
 				}`)
 			pkg1.Build()
 			pkg2.Build()
-			err := analyzer.Process(pkg1.Path, pkg2.Path)
+			err := analyzer.Process(buildTags, pkg1.Path, pkg2.Path)
 			Expect(err).ShouldNot(HaveOccurred())
 			_, metrics := analyzer.Report()
 			Expect(metrics.NumFiles).To(Equal(2))
@@ -104,7 +105,7 @@ var _ = Describe("Analyzer", func() {
 			defer controlPackage.Close()
 			controlPackage.AddFile("md5.go", source)
 			controlPackage.Build()
-			analyzer.Process(controlPackage.Path)
+			analyzer.Process(buildTags, controlPackage.Path)
 			controlIssues, _ := analyzer.Report()
 			Expect(controlIssues).Should(HaveLen(sample.Errors))
 
@@ -122,7 +123,7 @@ var _ = Describe("Analyzer", func() {
 			nosecPackage.AddFile("md5.go", nosecSource)
 			nosecPackage.Build()
 
-			analyzer.Process(nosecPackage.Path)
+			analyzer.Process(buildTags, nosecPackage.Path)
 			nosecIssues, _ := analyzer.Report()
 			Expect(nosecIssues).Should(BeEmpty())
 		})
@@ -139,7 +140,7 @@ var _ = Describe("Analyzer", func() {
 			nosecPackage.AddFile("md5.go", nosecSource)
 			nosecPackage.Build()
 
-			analyzer.Process(nosecPackage.Path)
+			analyzer.Process(buildTags, nosecPackage.Path)
 			nosecIssues, _ := analyzer.Report()
 			Expect(nosecIssues).Should(BeEmpty())
 		})
@@ -156,7 +157,7 @@ var _ = Describe("Analyzer", func() {
 			nosecPackage.AddFile("md5.go", nosecSource)
 			nosecPackage.Build()
 
-			analyzer.Process(nosecPackage.Path)
+			analyzer.Process(buildTags, nosecPackage.Path)
 			nosecIssues, _ := analyzer.Report()
 			Expect(nosecIssues).Should(HaveLen(sample.Errors))
 		})
@@ -173,10 +174,23 @@ var _ = Describe("Analyzer", func() {
 			nosecPackage.AddFile("md5.go", nosecSource)
 			nosecPackage.Build()
 
-			analyzer.Process(nosecPackage.Path)
+			analyzer.Process(buildTags, nosecPackage.Path)
 			nosecIssues, _ := analyzer.Report()
 			Expect(nosecIssues).Should(BeEmpty())
 		})
+
+		It("should pass the build tags", func() {
+			sample := testutils.SampleCode601[0]
+			source := sample.Code
+			analyzer.LoadRules(rules.Generate().Builders())
+			pkg := testutils.NewTestPackage()
+			defer pkg.Close()
+			pkg.AddFile("tags.go", source)
+
+			buildTags = append(buildTags, "test")
+			err := analyzer.Process(buildTags, pkg.Path)
+			Expect(err).Should(HaveOccurred())
+		})
 	})
 
 	It("should be possible to overwrite nosec comments, and report issues", func() {
@@ -197,7 +211,7 @@ var _ = Describe("Analyzer", func() {
 		nosecPackage.AddFile("md5.go", nosecSource)
 		nosecPackage.Build()
 
-		customAnalyzer.Process(nosecPackage.Path)
+		customAnalyzer.Process(buildTags, nosecPackage.Path)
 		nosecIssues, _ := customAnalyzer.Report()
 		Expect(nosecIssues).Should(HaveLen(sample.Errors))
 

cmd/gas/main.go

@@ -90,6 +90,9 @@ var (
 	// sort the issues by severity
 	flagSortIssues = flag.Bool("sort", true, "Sort issues by severity")
 
+	// go build tags
+	flagBuildTags = flag.String("tags", "", "Comma separated list of build tags")
+
 	logger *log.Logger
 )
 
@@ -313,7 +316,11 @@ func main() {
 		packages = append(packages, resolvePackage(pkg, gopaths))
 	}
 
-	if err := analyzer.Process(packages...); err != nil {
+	var buildTags []string
+	if *flagBuildTags != "" {
+		buildTags = strings.Split(*flagBuildTags, ",")
+	}
+	if err := analyzer.Process(buildTags, packages...); err != nil {
 		logger.Fatal(err)
 	}
 

rules/rules_test.go

@@ -19,6 +19,7 @@ var _ = Describe("gas rules", func() {
 		config    gas.Config
 		analyzer  *gas.Analyzer
 		runner    func(string, []testutils.CodeSample)
+		buildTags []string
 	)
 
 	BeforeEach(func() {
@@ -34,7 +35,7 @@ var _ = Describe("gas rules", func() {
 				pkg.AddFile(fmt.Sprintf("sample_%d.go", n), sample.Code)
 				err := pkg.Build()
 				Expect(err).ShouldNot(HaveOccurred())
-				err = analyzer.Process(pkg.Path)
+				err = analyzer.Process(buildTags, pkg.Path)
 				Expect(err).ShouldNot(HaveOccurred())
 				issues, _ := analyzer.Report()
 				if len(issues) != sample.Errors {

testutils/source.go

@@ -720,5 +720,13 @@ import (
  )
 func main() {
 	cgi.Serve(http.FileServer(http.Dir("/usr/share/doc")))
+}`, 1}}
+	// SampleCode601 - Go build tags
+	SampleCode601 = []CodeSample{{`
+// +build test
+
+package main
+func main() {
+  fmt.Println("no package imported error")
 }`, 1}}
 )