cmd/go: convert TestBuildDashIInstallsDependencies to a script test

Updates #28387
Updates #30316

Change-Id: I06e50c8d148cb4d7e08cdc2ba90de5e91d35781d
Reviewed-on: https://go-review.googlesource.com/c/go/+/207699
Run-TryBot: Bryan C. Mills <bcmills@google.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/cmd/go/go_test.go

@@ -2724,40 +2724,6 @@ func TestIssue6844(t *testing.T) {
 	tg.grepStderr("regexp", "go test -x -a -c testdata/dep-test.go did not rebuild regexp")
 }
 
-func TestBuildDashIInstallsDependencies(t *testing.T) {
-	tooSlow(t)
-
-	tg := testgo(t)
-	defer tg.cleanup()
-	tg.parallel()
-	tg.tempFile("src/x/y/foo/foo.go", `package foo
-		func F() {}`)
-	tg.tempFile("src/x/y/bar/bar.go", `package bar
-		import "x/y/foo"
-		func F() { foo.F() }`)
-	tg.setenv("GOPATH", tg.path("."))
-
-	// don't let build -i overwrite runtime
-	tg.wantNotStale("runtime", "", "must be non-stale before build -i")
-
-	checkbar := func(desc string) {
-		tg.run("build", "-v", "-i", "x/y/bar")
-		tg.grepBoth("x/y/foo", "first build -i "+desc+" did not build x/y/foo")
-		tg.run("build", "-v", "-i", "x/y/bar")
-		tg.grepBothNot("x/y/foo", "second build -i "+desc+" built x/y/foo")
-	}
-	checkbar("pkg")
-
-	tg.creatingTemp("bar" + exeSuffix)
-	tg.sleep()
-	tg.tempFile("src/x/y/foo/foo.go", `package foo
-		func F() { F() }`)
-	tg.tempFile("src/x/y/bar/bar.go", `package main
-		import "x/y/foo"
-		func main() { foo.F() }`)
-	checkbar("cmd")
-}
-
 func TestGoBuildTestOnly(t *testing.T) {
 	tg := testgo(t)
 	defer tg.cleanup()

src/cmd/go/testdata/script/build_i.txt

@@ -0,0 +1,41 @@
+env GO111MODULE=off
+
+# Test that 'go build -i' installs dependencies of the requested package.
+
+[short] skip
+
+# Since we are checking installation of dependencies, use a clean cache
+# to ensure that multiple runs of the test do not interfere.
+env GOCACHE=$WORK/cache
+
+# The initial 'go build -i' for bar should install its dependency foo.
+
+go build -v -i x/y/bar
+stderr 'x/y/foo'    # should be rebuilt
+go build -v -i x/y/bar
+! stderr 'x/y/foo'  # should already be installed
+
+# After modifying the source files, both packages should be rebuild.
+
+cp x/y/foo/foo.go.next x/y/foo/foo.go
+cp x/y/bar/bar.go.next x/y/bar/bar.go
+
+go build -v -i x/y/bar
+stderr 'x/y/foo'    # should be rebuilt
+go build -v -i x/y/bar
+! stderr 'x/y/foo'  # should already be installed
+
+-- x/y/foo/foo.go --
+package foo
+func F() {}
+-- x/y/bar/bar.go --
+package bar
+import "x/y/foo"
+func F() { foo.F() }
+-- x/y/foo/foo.go.next --
+package foo
+func F() { F() }
+-- x/y/bar/bar.go.next --
+package main
+import "x/y/foo"
+func main() { foo.F() }