From 22ccbbaae82ca62d7b25f2c5e4f2fd280d255801 Mon Sep 17 00:00:00 2001
From: Owen Mansel-Chan <owen-mc@github.com>
Date: Tue, 3 May 2022 14:57:13 +0100
Subject: [PATCH] Run `go mod tidy -e` if go.mod exists

---
 .../cli/go-autobuilder/go-autobuilder.go      | 74 ++++++++++++++++++-
 1 file changed, 73 insertions(+), 1 deletion(-)

diff --git a/extractor/cli/go-autobuilder/go-autobuilder.go b/extractor/cli/go-autobuilder/go-autobuilder.go
index daaf733f88a..d37e1293a91 100644
--- a/extractor/cli/go-autobuilder/go-autobuilder.go
+++ b/extractor/cli/go-autobuilder/go-autobuilder.go
@@ -2,7 +2,6 @@ package main
 
 import (
 	"fmt"
-	"golang.org/x/mod/semver"
 	"io/ioutil"
 	"log"
 	"net/url"
@@ -13,6 +12,8 @@ import (
 	"runtime"
 	"strings"
 
+	"golang.org/x/mod/semver"
+
 	"github.com/github/codeql-go/extractor/autobuilder"
 	"github.com/github/codeql-go/extractor/util"
 )
@@ -289,6 +290,77 @@ func main() {
 		}
 	}
 
+	if depMode == GoGetWithModules {
+		// stat go.mod and go.sum
+		var beforeGoModFileInfo, beforeGoSumFileInfo os.FileInfo
+
+		beforeGoMod, beforeGoModerr := os.Open("go.mod")
+		if beforeGoModerr == nil {
+			var beforeGoModStatErr error
+			beforeGoModFileInfo, beforeGoModStatErr = beforeGoMod.Stat()
+			if beforeGoModStatErr != nil {
+				log.Println("Failed to stat go.mod before running `go mod tidy -e`")
+			}
+		} else {
+			log.Println("Failed to read go.mod before running `go mod tidy -e`")
+		}
+		beforeGoMod.Close()
+
+		beforeGoSum, beforeGoSumErr := os.Open("go.sum")
+		if beforeGoSumErr == nil {
+			var beforeGoSumStatErr error
+			beforeGoSumFileInfo, beforeGoSumStatErr = beforeGoSum.Stat()
+			if beforeGoSumStatErr != nil {
+				log.Println("Failed to stat go.sum before running `go mod tidy -e`")
+			}
+		}
+		// don't print a warning if beforeGoSumErr != nil as it may be that the
+		// file doesn't exist
+		beforeGoSum.Close()
+
+		// run `go mod tidy -e`
+		res := util.RunCmd(exec.Command("go", "mod", "tidy", "-e"))
+
+		if !res {
+			log.Println("Failed to run `go mod tidy -e`")
+		} else {
+			if beforeGoModFileInfo != nil {
+				afterGoMod, afterGoModErr := os.Open("go.mod")
+				if afterGoModErr != nil {
+					log.Println("Failed to read go.mod after running `go mod tidy -e`")
+				} else {
+					afterGoModFileInfo, afterGoModStatErr := afterGoMod.Stat()
+					if afterGoModStatErr != nil {
+						log.Println("Failed to stat go.mod after running `go mod tidy -e`")
+					} else {
+						if afterGoModFileInfo.ModTime().After(beforeGoModFileInfo.ModTime()) {
+							// if go.mod has been changed then notify the user
+							log.Println("We have run `go mod tidy -e` and it altered go.mod. You may wish to check these changes into version control. ")
+						}
+					}
+				}
+				afterGoMod.Close()
+			}
+
+			afterGoSum, afterGoSumErr := os.Open("go.sum")
+			if afterGoSumErr != nil {
+				log.Println("Failed to read go.sum after running `go mod tidy -e`")
+			} else {
+				afterGoSumFileInfo, afterGoSumStatErr := afterGoSum.Stat()
+				if afterGoSumStatErr != nil {
+					log.Println("Failed to stat go.sum after running `go mod tidy -e`")
+				} else {
+					if beforeGoSumErr != nil || afterGoSumFileInfo.ModTime().After(beforeGoSumFileInfo.ModTime()) {
+						// if go.sum has been changed then notify the user
+						log.Println("We have run `go mod tidy -e` and it altered go.sum. You may wish to check these changes into version control. ")
+					}
+				}
+			}
+			afterGoSum.Close()
+
+		}
+	}
+
 	// if `LGTM_INDEX_NEED_GOPATH` is set, it overrides the value for `needGopath` inferred above
 	if needGopathOverride := os.Getenv("LGTM_INDEX_NEED_GOPATH"); needGopathOverride != "" {
 		inLGTM = true