cmd/go: document 'go env GOMOD' outside modules

In documentation for 'go env GOMOD', note that the path will be
os.DevNull in module-aware mode when no go.mod file is present.

Fixes #36052

Change-Id: I30ced1df02ccefe1970bd856190e79d6f0384375
Reviewed-on: https://go-review.googlesource.com/c/go/+/210577
Run-TryBot: Jay Conrod <jayconrod@google.com>
Reviewed-by: Bryan C. Mills <bcmills@google.com>

diff --git a/src/cmd/go/alldocs.go b/src/cmd/go/alldocs.go
index 87c82b16de1144c04ea4f4a910d755093aac35b1..54e7a8b5b300edb89ae7c0cda580a1aa1578a1a6 100644 (file)
--- a/src/cmd/go/alldocs.go
+++ b/src/cmd/go/alldocs.go
@@ -1726,8 +1726,10 @@
 //     GOHOSTOS
 //             The operating system (GOOS) of the Go toolchain binaries.
 //     GOMOD
-//             The absolute path to the go.mod of the main module,
-//             or the empty string if not using modules.
+//             The absolute path to the go.mod of the main module.
+//             If module-aware mode is enabled, but there is no go.mod, GOMOD will be
+//             os.DevNull ("/dev/null" on Unix-like systems, "NUL" on Windows).
+//             If module-aware mode is disabled, GOMOD will be the empty string.
 //     GOTOOLDIR
 //             The directory where the go tools (compile, cover, doc, etc...) are installed.
 //

diff --git a/src/cmd/go/internal/help/helpdoc.go b/src/cmd/go/internal/help/helpdoc.go
index ac16312aaf437d46da883a9e2fcc31df29b8431c..6a843f459a8dd994338ef864ed65f939b28d3080 100644 (file)
--- a/src/cmd/go/internal/help/helpdoc.go
+++ b/src/cmd/go/internal/help/helpdoc.go
@@ -621,8 +621,10 @@ Additional information available from 'go env' but not read from the environment
        GOHOSTOS
                The operating system (GOOS) of the Go toolchain binaries.
        GOMOD
-               The absolute path to the go.mod of the main module,
-               or the empty string if not using modules.
+               The absolute path to the go.mod of the main module.
+               If module-aware mode is enabled, but there is no go.mod, GOMOD will be
+               os.DevNull ("/dev/null" on Unix-like systems, "NUL" on Windows).
+               If module-aware mode is disabled, GOMOD will be the empty string.
        GOTOOLDIR
                The directory where the go tools (compile, cover, doc, etc...) are installed.
        `,