Fix isGenerated to work with license message at top of files

_fixtures/generated_license.go

@@ -0,0 +1,32 @@
+// MIT License
+//
+// Copyright (c) 2019 Segment.io, Inc.
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all
+// copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+
+// generated by something DO NOT EDIT
+
+package fixtures
+
+import "fmt"
+
+func testFunc() {
+	fmt.Printf("This is a really long line that can be broken up twice %s %s", fmt.Sprintf("This is a really long sub-line that should be broken up more because %s %s", argument1, argument2), fmt.Sprintf("A short one %d", 3))
+	fmt.Print("This is a function with a really long single argument. We want to see if it's properly split")
+}

_fixtures/generated_license__exp.go

@@ -0,0 +1,32 @@
+// MIT License
+//
+// Copyright (c) 2019 Segment.io, Inc.
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all
+// copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+
+// generated by something DO NOT EDIT
+
+package fixtures
+
+import "fmt"
+
+func testFunc() {
+	fmt.Printf("This is a really long line that can be broken up twice %s %s", fmt.Sprintf("This is a really long sub-line that should be broken up more because %s %s", argument1, argument2), fmt.Sprintf("A short one %d", 3))
+	fmt.Print("This is a function with a really long single argument. We want to see if it's properly split")
+}

shortener.go

@@ -592,17 +592,23 @@ func (s *Shortener) formatSpec(spec dst.Spec, force bool) {
 }
 
 // isGenerated checks whether the provided file bytes are from a generated file.
-// This is done by looking for a set of typically-used strings in the first 5 lines.
+// It checks the lines from the top of the file while they are comments or empty.
+// This ensures it skips the license message that are often placed at the top of files.
+// For backwards compatibility, it reads at least 5 lines.
 func (s *Shortener) isGenerated(contents []byte) bool {
 	scanner := bufio.NewScanner(bytes.NewBuffer(contents))
 
 	for i := 0; scanner.Scan(); i++ {
-		if i >= 5 {
+		line := strings.TrimSpace(strings.ToLower(scanner.Text()))
+		if len(line) == 0 {
+			continue
+		}
+		if i >= 5 && !strings.HasPrefix(line, "//") {
 			return false
 		}
 
 		for _, term := range generatedTerms {
-			if strings.Contains(strings.ToLower(scanner.Text()), term) {
+			if strings.Contains(line, term) {
 				return true
 			}
 		}