Add sys: module to expose platform and arch vars

Resolves #916

pkg/eval/sys/sys.go

@@ -0,0 +1,25 @@
+// Package sys exposes variables and functions that deal with the specific
+// system being run on. Such as the OS name and CPU architecture.
+package sys
+
+import (
+	"runtime"
+
+	"github.com/elves/elvish/pkg/eval"
+	"github.com/elves/elvish/pkg/eval/vars"
+)
+
+//elvdoc:var arch
+//
+// The architecture of the platform; e.g., amd64, arm, ppc. This is read-only.
+
+//elvdoc:var platform
+//
+// The name of the platform; e.g., darwin (macOS), linux. This is read-only.
+
+var Ns = eval.NewNs()
+
+func init() {
+	Ns.Add("arch", vars.NewReadOnly(runtime.GOARCH))
+	Ns.Add("platform", vars.NewReadOnly(runtime.GOOS))
+}

pkg/eval/sys/sys_test.go

@@ -0,0 +1,17 @@
+package sys
+
+import (
+	"runtime"
+	"testing"
+
+	"github.com/elves/elvish/pkg/eval"
+)
+
+func TestMath(t *testing.T) {
+	setup := func(ev *eval.Evaler) { ev.Builtin.AddNs("sys", Ns) }
+	That := eval.That
+	eval.TestWithSetup(t, setup,
+		That(`put $sys:arch`).Puts(runtime.GOARCH),
+		That(`put $sys:platform`).Puts(runtime.GOOS),
+	)
+}

pkg/program/shell/runtime.go

@@ -15,6 +15,7 @@ import (
 	"github.com/elves/elvish/pkg/eval/re"
 	"github.com/elves/elvish/pkg/eval/store"
 	"github.com/elves/elvish/pkg/eval/str"
+	"github.com/elves/elvish/pkg/eval/sys"
 	daemonp "github.com/elves/elvish/pkg/program/daemon"
 )
 
@@ -74,6 +75,7 @@ func InitRuntime(binpath, sockpath, dbpath string) (*eval.Evaler, string) {
 	ev.InstallModule("math", eval.MathNs)
 	ev.InstallModule("re", re.Ns)
 	ev.InstallModule("str", str.Ns)
+	ev.InstallModule("sys", sys.Ns)
 	if sockpath != "" && dbpath != "" {
 		spawner := &daemonp.Daemon{
 			BinPath:       binpath,

website/ref/index.toml

@@ -14,6 +14,10 @@ title = "The Editor Module (edit:)"
 name = "re"
 title = "The Regular Expression Module (re:)"
 
+[[articles]]
+name = "sys"
+title = "The System Module (sys:)"
+
 [[articles]]
 name = "epm"
 title = "The Elvish Package Manager (epm:)"

website/ref/sys.md

@@ -0,0 +1,10 @@
+<!-- toc -->
+
+# Introduction
+
+The `sys:` module provides platform specific functions and constants.
+
+Function usages are given in the same format as in the
+reference doc for the [builtin module](builtin.html).
+
+@elvdoc -ns sys: -dir ../pkg/eval/sys