Make dev print only logs that arrive after its first upload

internal/dev/dev.go

@@ -68,7 +68,7 @@ func Dev(invocation api.Invocation, arguments []string) error {
 	tailEnded := make(chan error, 1)
 
 	go func() {
-		tailEnded <- tail.Tail(invocation, tailArguments)
+		tailEnded <- tail.Follow(invocation, tailArguments, true)
 	}()
 
 	// Upload again once the watched paths have changed and then stayed still for one poll

internal/dev/dev_test.go

@@ -6,6 +6,7 @@ import (
 	"net/http"
 	"os"
 	"path/filepath"
+	"slices"
 	"strings"
 	"sync"
 	"testing"
@@ -147,22 +148,22 @@ func TestDevUploadsOnChangeAndFollowsTheLog(t *testing.T) {
 		name         string
 		target       string
 		watchFile    bool
-		wantQuery    string
+		wantQueries  []string
 		wantUploaded string
 		wantRefusal  string
 	}{
 		{
 			name:         "a file to a device",
 			target:       "354820091234567",
 			watchFile:    true,
-			wantQuery:    "after=2&imei=354820091234567",
+			wantQueries:  []string{"imei=354820091234567&last=1", "after=2&imei=354820091234567"},
 			wantUploaded: "Uploaded 1 file to device 354820091234567. It arrives at its next check-in.\n",
 			wantRefusal:  "does not exist",
 		},
 		{
 			name:         "a directory to a fleet",
 			target:       "3",
-			wantQuery:    "after=2",
+			wantQueries:  []string{"last=1", "after=2"},
 			wantUploaded: "Uploaded 1 file to 2 devices in fleet 3. It arrives at each device's next check-in.\n",
 			wantRefusal:  "there are no files to upload",
 		},
@@ -226,8 +227,8 @@ func TestDevUploadsOnChangeAndFollowsTheLog(t *testing.T) {
 			server.mutex.Lock()
 			defer server.mutex.Unlock()
 
-			if len(server.queries) < 2 || server.queries[1] != test.wantQuery {
-				t.Errorf("log queries were %q, want the follow to ask %q", server.queries, test.wantQuery)
+			if len(server.queries) < 2 || !slices.Equal(server.queries[:2], test.wantQueries) {
+				t.Errorf("log queries were %q, want them to start %q", server.queries, test.wantQueries)
 			}
 
 			wantBodies := []string{
@@ -248,8 +249,8 @@ func TestDevUploadsOnChangeAndFollowsTheLog(t *testing.T) {
 				t.Errorf("output was:\n%s\nwant %q three times", output, test.wantUploaded)
 			}
 
-			if !strings.Contains(output, "[boiler] log 1\n") || !strings.Contains(output, "[boiler] log 2\n") {
-				t.Errorf("output was:\n%s\nwant the two stored logs", output)
+			if strings.Contains(output, "[boiler] log") {
+				t.Errorf("output was:\n%s\nwant none of the logs stored before the first upload", output)
 			}
 
 			if !strings.HasPrefix(output, test.wantUploaded) {

internal/tail/tail.go

@@ -14,6 +14,11 @@ import (
 )
 
 func Tail(invocation api.Invocation, arguments []string) error {
+	return Follow(invocation, arguments, false)
+}
+
+// Takes tail's arguments. fromNow leaves out every log stored before the follow starts
+func Follow(invocation api.Invocation, arguments []string, fromNow bool) error {
 	positionals := []string{}
 	count := int64(0)
 	offset := int64(0)
@@ -98,14 +103,20 @@ func Tail(invocation api.Invocation, arguments []string) error {
 	// The newest logs, then follow
 	query.Set("last", "100")
 
+	if fromNow {
+		query.Set("last", "1")
+	}
+
 	answer, err := api.FetchLogs(invocation, fleetID, query)
 
 	if err != nil {
 		return err
 	}
 
-	for _, entry := range answer.Logs {
-		printLog(invocation.Out, entry)
+	if !fromNow {
+		for _, entry := range answer.Logs {
+			printLog(invocation.Out, entry)
+		}
 	}
 
 	query.Del("last")

internal/tail/tail_test.go

@@ -240,41 +240,67 @@ func TestTailPrintsEachLogSafely(t *testing.T) {
 }
 
 func TestTailFollows(t *testing.T) {
-	logs := testLogs(7)
-	server := &testLogServer{
-		logs: logs[:5],
-		follow: []*api.LogsAnswer{
-			{Logs: logs[5:6]},
-			nil,
-			{Logs: []api.LogEntry{}, Next: 6},
-			{Logs: logs[6:7]},
+	tests := []struct {
+		name       string
+		follow     func(invocation api.Invocation, arguments []string) error
+		wantTexts  []string
+		wantNewest string
+	}{
+		{
+			name:       "after the newest logs",
+			follow:     Tail,
+			wantTexts:  []string{"log 2", "log 4", "log 6", "log 7"},
+			wantNewest: "imei=222222222222222&last=100",
+		},
+		{
+			name: "from now",
+			follow: func(invocation api.Invocation, arguments []string) error {
+				return Follow(invocation, arguments, true)
+			},
+			wantTexts:  []string{"log 6", "log 7"},
+			wantNewest: "imei=222222222222222&last=1",
 		},
 	}
-	invocation, out := apitest.LoggedInInvocation(t, server)
 
-	err := Tail(invocation, []string{"3", "222222222222222"})
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			logs := testLogs(7)
+			server := &testLogServer{
+				logs: logs[:5],
+				follow: []*api.LogsAnswer{
+					{Logs: logs[5:6]},
+					nil,
+					{Logs: []api.LogEntry{}, Next: 6},
+					{Logs: logs[6:7]},
+				},
+			}
+			invocation, out := apitest.LoggedInInvocation(t, server)
 
-	if err == nil || err.Error() != "no such fleet" {
-		t.Fatalf("error = %v, want the server's refusal that ends the follow", err)
-	}
+			err := test.follow(invocation, []string{"3", "222222222222222"})
 
-	texts := printedTexts(out.String())
+			if err == nil || err.Error() != "no such fleet" {
+				t.Fatalf("error = %v, want the server's refusal that ends the follow", err)
+			}
 
-	if !slices.Equal(texts, []string{"log 2", "log 4", "log 6", "log 7"}) {
-		t.Errorf("printed %q, want the newest logs then the ones that arrived while following", texts)
-	}
+			texts := printedTexts(out.String())
 
-	wantQueries := []string{
-		"imei=222222222222222&last=100",
-		"after=4&imei=222222222222222",
-		"after=6&imei=222222222222222",
-		"after=6&imei=222222222222222",
-		"after=6&imei=222222222222222",
-		"after=7&imei=222222222222222",
-	}
+			if !slices.Equal(texts, test.wantTexts) {
+				t.Errorf("printed %q, want %q", texts, test.wantTexts)
+			}
 
-	if !slices.Equal(server.queries, wantQueries) {
-		t.Errorf("asked %q, want %q", server.queries, wantQueries)
+			wantQueries := []string{
+				test.wantNewest,
+				"after=4&imei=222222222222222",
+				"after=6&imei=222222222222222",
+				"after=6&imei=222222222222222",
+				"after=6&imei=222222222222222",
+				"after=7&imei=222222222222222",
+			}
+
+			if !slices.Equal(server.queries, wantQueries) {
+				t.Errorf("asked %q, want %q", server.queries, wantQueries)
+			}
+		})
 	}
 }
 

main.go

@@ -53,7 +53,7 @@ var sections = []dispatch.Section{
 		Commands: []dispatch.Command{
 			{Name: "upload", Arguments: "<imei|fleet_id> <file> ...", Summary: "Upload files or directories to a device or fleet", Run: files.Upload},
 			{Name: "download", Arguments: "<imei> <path>", Summary: "Download the code last uploaded to a device into <path>", Run: files.Download},
-			{Name: "dev", Arguments: "<imei|fleet_id> <file> ...", Summary: "Upload on every change, and tail", Run: dev.Dev},
+			{Name: "dev", Arguments: "<imei|fleet_id> <file> ...", Summary: "Upload on every change, and follow the log from the first upload", Run: dev.Dev},
 		},
 	},
 	{