Fix CmdLine generation and caching

CHANGELOG.md

@@ -15,6 +15,8 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 
 ### Fixed
 
+ - Fix CmdLine generation and caching for system.process
+
 ## [0.7.0]
 
 ### Added

metric/system/process/process.go

@@ -222,6 +222,9 @@ func (procStats *Stats) pidFill(pid int, filter bool) (ProcState, bool, error) {
 	if procStats.skipExtended {
 		return status, true, nil
 	}
+
+	// Some OSes use the cache to avoid expensive system calls,
+	// cacheCmdLine reads from the cache.
 	status = procStats.cacheCmdLine(status)
 
 	// Filter based on user-supplied func
@@ -236,9 +239,7 @@ func (procStats *Stats) pidFill(pid int, filter bool) (ProcState, bool, error) {
 	if err != nil {
 		return status, true, fmt.Errorf("FillPidMetrics: %w", err)
 	}
-	if len(status.Args) > 0 && status.Cmdline == "" {
-		status.Cmdline = strings.Join(status.Args, " ")
-	}
+
 	if status.CPU.Total.Ticks.Exists() {
 		status.CPU.Total.Value = opt.FloatWith(metric.Round(float64(status.CPU.Total.Ticks.ValueOr(0))))
 	}
@@ -266,6 +267,12 @@ func (procStats *Stats) pidFill(pid int, filter bool) (ProcState, bool, error) {
 		return status, true, fmt.Errorf("FillMetricsRequiringMoreAccess: %w", err)
 	}
 
+	// Generate `status.Cmdline` here for compatibility because on Windows
+	// `status.Args` is set by `FillMetricsRequiringMoreAccess`.
+	if len(status.Args) > 0 && status.Cmdline == "" {
+		status.Cmdline = strings.Join(status.Args, " ")
+	}
+
 	// network data
 	if procStats.EnableNetwork {
 		procHandle, err := sysinfo.Process(pid)

metric/system/process/process_test.go

@@ -279,6 +279,8 @@ func TestGetProcess(t *testing.T) {
 	case "linux":
 		assert.True(t, (len(process.Cwd) > 0))
 	}
+
+	assert.NotEmptyf(t, process.Cmdline, "cmdLine must be present")
 }
 
 func TestMatchProcs(t *testing.T) {