Abstract table writing to xtabwriter

coder · cmoog · Jul 31, 2020 · Jul 31, 2020 · Jul 31, 2020 · Jul 31, 2020
commit b0e06c41981eda5f87736f198e6c103d26b44f6c
diff --git a/cmd/coder/envs.go b/cmd/coder/envs.go
@@ -2,7 +2,6 @@ package main
 
 import (
 	"encoding/json"
-	"fmt"
 	"os"
 
 	"cdr.dev/coder-cli/internal/x/xtabwriter"
@@ -30,17 +29,10 @@ func makeEnvsCommand() cli.Command {
 
 					switch outputFmt {
 					case "human":
-						w := xtabwriter.NewWriter()
-						if len(envs) > 0 {
-							_, err := fmt.Fprintln(w, xtabwriter.StructFieldNames(envs[0]))
-							requireSuccess(err, "failed to write header: %v", err)
-						}
-						for _, env := range envs {
-							_, err := fmt.Fprintln(w, xtabwriter.StructValues(env))
-							requireSuccess(err, "failed to write row: %v", err)
-						}
-						err := w.Flush()
-						requireSuccess(err, "failed to flush tab writer: %v", err)
+						err := xtabwriter.WriteTable(len(envs), func(i int) interface{} {
+							return envs[i]
+						})
+						requireSuccess(err, "failed to write table: %v", err)
 					case "json":
 						err := json.NewEncoder(os.Stdout).Encode(envs)
 						requireSuccess(err, "failed to write json: %v", err)

diff --git a/cmd/coder/users.go b/cmd/coder/users.go
@@ -2,7 +2,6 @@ package main
 
 import (
 	"encoding/json"
-	"fmt"
 	"os"
 
 	"cdr.dev/coder-cli/internal/x/xtabwriter"
@@ -44,17 +43,10 @@ func listUsers(outputFmt *string) func(c *cli.Context) {
 
 		switch *outputFmt {
 		case "human":
-			w := xtabwriter.NewWriter()
-			if len(users) > 0 {
-				_, err = fmt.Fprintln(w, xtabwriter.StructFieldNames(users[0]))
-				requireSuccess(err, "failed to write: %v", err)
-			}
-			for _, u := range users {
-				_, err = fmt.Fprintln(w, xtabwriter.StructValues(u))
-				requireSuccess(err, "failed to write: %v", err)
-			}
-			err = w.Flush()
-			requireSuccess(err, "failed to flush writer: %v", err)
+			err := xtabwriter.WriteTable(len(users), func(i int) interface{} {
+				return users[i]
+			})
+			requireSuccess(err, "failed to write table: %v", err)
 		case "json":
 			err = json.NewEncoder(os.Stdout).Encode(users)
 			requireSuccess(err, "failed to encode users to json: %v", err)

diff --git a/internal/x/xtabwriter/tabwriter.go b/internal/x/xtabwriter/tabwriter.go
@@ -46,6 +46,32 @@ func StructFieldNames(data interface{}) string {
 	return s.String()
 }
 
+// WriteTable writes the given list elements to stdout in a human readable
+// tabular format. Headers abide by the `tab` struct tag.
+//
+// `tab:"-"` omits the field and no tag defaults to the Go identifier.
+func WriteTable(length int, each func(i int) interface{}) error {
+	if length < 1 {
+		return nil
+	}
+	w := NewWriter()
+	defer w.Flush()
+	for ix := 0; ix < length; ix++ {
+		item := each(ix)
+		if ix == 0 {
+			_, err := fmt.Fprintln(w, StructFieldNames(item))
+			if err != nil {
+				return err
+			}
+		}
+		_, err := fmt.Fprintln(w, StructValues(item))
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
 func shouldHideField(f reflect.StructField) bool {
 	return f.Tag.Get(structFieldTagKey) == "-"
 }