cmd/go: fix TestScript/build_trimpath_goroot when built with a mismatched GOROOT_FINAL

Fixes #52236.
Updates #51461.

Change-Id: Ie91e0256afd45e9bbd60fd8cdc696363027ab696
Reviewed-on: https://go-review.googlesource.com/c/go/+/399156
Run-TryBot: Bryan Mills <bcmills@google.com>
Reviewed-by: Russ Cox <rsc@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>

src/cmd/go/go_test.go

@@ -78,6 +78,10 @@ func tooSlow(t *testing.T) {
 // (temp) directory.
 var testGOROOT string
 
+// testGOROOT_FINAL is the GOROOT_FINAL with which the test binary is assumed to
+// have been built.
+var testGOROOT_FINAL = os.Getenv("GOROOT_FINAL")
+
 var testGOCACHE string
 
 var testGo string

src/cmd/go/script_test.go

@@ -175,7 +175,7 @@ func (ts *testScript) setup() {
 		"GOPROXY=" + proxyURL,
 		"GOPRIVATE=",
 		"GOROOT=" + testGOROOT,
-		"GOROOT_FINAL=" + os.Getenv("GOROOT_FINAL"), // causes spurious rebuilds and breaks the "stale" built-in if not propagated
+		"GOROOT_FINAL=" + testGOROOT_FINAL, // causes spurious rebuilds and breaks the "stale" built-in if not propagated
 		"GOTRACEBACK=system",
 		"TESTGO_GOROOT=" + testGOROOT,
 		"GOSUMDB=" + testSumDBVerifierKey,
@@ -385,6 +385,8 @@ Script:
 						}
 					}
 				}
+			case "mismatched-goroot":
+				ok = testGOROOT_FINAL != "" && testGOROOT_FINAL != testGOROOT
 			default:
 				if strings.HasPrefix(cond.tag, "exec:") {
 					prog := cond.tag[len("exec:"):]

src/cmd/go/testdata/script/README

@@ -90,6 +90,8 @@ should only run when the condition is satisfied. The available conditions are:
    - [exec:prog] for whether prog is available for execution (found by exec.LookPath)
    - [GODEBUG:value] for whether value is one of the comma-separated entries in the GODEBUG variable
    - [buildmode:value] for whether -buildmode=value is supported
+   - [trimpath] for whether the 'go' binary was built with -trimpath
+   - [mismatched-goroot] for whether the test's GOROOT_FINAL does not match the real GOROOT
 
 A condition can be negated: [!short] means to run the rest of the line
 when testing.Short() is false. Multiple conditions may be given for a single

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

@@ -8,23 +8,51 @@
 # TODO(#51483): when runtime.GOROOT() returns the empty string,
 # go/build should default to 'go env GOROOT' instead.
 
-env GOROOT=
 env GOROOT_FINAL=
 
+[trimpath] env GOROOT=
 [trimpath] ! go env GOROOT
 [trimpath] stderr '^go: cannot find GOROOT directory: ''go'' binary is trimmed and GOROOT is not set$'
+[trimpath] env GOROOT=$TESTGO_GOROOT
+
+[short] stop
+
+# With GOROOT still set but GOROOT_FINAL unset, 'go build' and 'go test -c'
+# should cause runtime.GOROOT() to report either the correct GOROOT
+# (without -trimpath) or no GOROOT at all (with -trimpath).
+
+go build -o example.exe .
+go build -trimpath -o example-trimpath.exe .
+go test -c -o example.test.exe .
+go test -trimpath -c -o example.test-trimpath.exe .
+
+env GOROOT=
+
+exec ./example.exe
+stdout '^GOROOT '$TESTGO_GOROOT'$'
+stdout '^runtime '$TESTGO_GOROOT${/}src${/}runtime'$'
+
+! exec ./example-trimpath.exe
+stdout '^GOROOT $'
+stderr 'cannot find package "runtime" in any of:\n\t\(\$GOROOT not set\)\n\t'$WORK${/}gopath${/}src${/}runtime' \(from \$GOPATH\)\n\z'
+
+exec ./example.test.exe -test.v
+stdout '^GOROOT '$TESTGO_GOROOT'$'
+stdout '^runtime '$TESTGO_GOROOT${/}src${/}runtime'$'
+
+! exec ./example.test-trimpath.exe -test.v
+stdout '^GOROOT $'
+stderr 'cannot find package "runtime" in any of:\n\t\(\$GOROOT not set\)\n\t'$WORK${/}gopath${/}src${/}runtime' \(from \$GOPATH\)$'
+
+# If a correct GOROOT is baked in to the 'go' command itself, 'go run' and
+# 'go test' should not implicitly set GOROOT in the process environment
+# (because that could mask an unexpected production dependency on the GOROOT
+# environment variable), but 'go generate' should (because the generator may
+# reasonably expect to be able to locate the GOROOT for which it is generating
+# code).
+
 [trimpath] stop
-
-
-[short] skip
-
-go run .
-stdout '^GOROOT '$TESTGO_GOROOT'$'
-stdout '^runtime '$TESTGO_GOROOT${/}src${/}runtime'$'
-
-go test -v .
-stdout '^GOROOT '$TESTGO_GOROOT'$'
-stdout '^runtime '$TESTGO_GOROOT${/}src${/}runtime'$'
+[mismatched-goroot] stop
 
 ! go run -trimpath .
 stdout '^GOROOT $'