Ensure that commands print to a colorable output

If a command does `fmt.Print(...)` for output that contains ANSI color
codes, this not safe on Windows. We have to ensure that we always use
the `fmt.Fprint*` family of functions with a writer that was transformed
using `utils.NewColorable()`.

command/issue.go

@@ -2,6 +2,7 @@ package command
 
 import (
 	"fmt"
+	"io"
 	"os"
 	"strconv"
 	"strings"
@@ -94,12 +95,15 @@ func issueList(cmd *cobra.Command, args []string) error {
 		return err
 	}
 
+	out := cmd.OutOrStdout()
+	colorOut := colorableOut(cmd)
+
 	if len(issues) == 0 {
-		printMessage("There are no open issues")
+		printMessage(colorOut, "There are no open issues")
 		return nil
 	}
 
-	table := utils.NewTablePrinter(cmd.OutOrStdout())
+	table := utils.NewTablePrinter(out)
 	for _, issue := range issues {
 		issueNum := strconv.Itoa(issue.Number)
 		if table.IsTTY() {
@@ -141,30 +145,32 @@ func issueStatus(cmd *cobra.Command, args []string) error {
 		return err
 	}
 
-	printHeader("Issues assigned to you")
+	out := colorableOut(cmd)
+
+	printHeader(out, "Issues assigned to you")
 	if issuePayload.Assigned != nil {
-		printIssues("  ", issuePayload.Assigned...)
+		printIssues(out, "  ", issuePayload.Assigned...)
 	} else {
 		message := fmt.Sprintf("  There are no issues assgined to you")
-		printMessage(message)
+		printMessage(out, message)
 	}
-	fmt.Println()
+	fmt.Fprintln(out)
 
-	printHeader("Issues mentioning you")
+	printHeader(out, "Issues mentioning you")
 	if len(issuePayload.Mentioned) > 0 {
-		printIssues("  ", issuePayload.Mentioned...)
+		printIssues(out, "  ", issuePayload.Mentioned...)
 	} else {
-		printMessage("  There are no issues mentioning you")
+		printMessage(out, "  There are no issues mentioning you")
 	}
-	fmt.Println()
+	fmt.Fprintln(out)
 
-	printHeader("Issues opened by you")
+	printHeader(out, "Issues opened by you")
 	if len(issuePayload.Authored) > 0 {
-		printIssues("  ", issuePayload.Authored...)
+		printIssues(out, "  ", issuePayload.Authored...)
 	} else {
-		printMessage("  There are no issues opened by you")
+		printMessage(out, "  There are no issues opened by you")
 	}
-	fmt.Println()
+	fmt.Fprintln(out)
 
 	return nil
 }
@@ -255,14 +261,14 @@ func issueCreate(cmd *cobra.Command, args []string) error {
 	return nil
 }
 
-func printIssues(prefix string, issues ...api.Issue) {
+func printIssues(w io.Writer, prefix string, issues ...api.Issue) {
 	for _, issue := range issues {
 		number := utils.Green("#" + strconv.Itoa(issue.Number))
 		coloredLabels := labelList(issue)
 		if coloredLabels != "" {
 			coloredLabels = utils.Gray(fmt.Sprintf("  (%s)", coloredLabels))
 		}
-		fmt.Printf("%s%s %s%s\n", prefix, number, truncate(70, issue.Title), coloredLabels)
+		fmt.Fprintf(w, "%s%s %s%s\n", prefix, number, truncate(70, issue.Title), coloredLabels)
 	}
 }
 

command/pr.go

@@ -2,6 +2,7 @@ package command
 
 import (
 	"fmt"
+	"io"
 	"os"
 	"os/exec"
 	"strconv"
@@ -78,30 +79,32 @@ func prStatus(cmd *cobra.Command, args []string) error {
 		return err
 	}
 
-	printHeader("Current branch")
+	out := colorableOut(cmd)
+
+	printHeader(out, "Current branch")
 	if prPayload.CurrentPR != nil {
-		printPrs(*prPayload.CurrentPR)
+		printPrs(out, *prPayload.CurrentPR)
 	} else {
 		message := fmt.Sprintf("  There is no pull request associated with %s", utils.Cyan("["+currentBranch+"]"))
-		printMessage(message)
+		printMessage(out, message)
 	}
-	fmt.Println()
+	fmt.Fprintln(out)
 
-	printHeader("Created by you")
+	printHeader(out, "Created by you")
 	if len(prPayload.ViewerCreated) > 0 {
-		printPrs(prPayload.ViewerCreated...)
+		printPrs(out, prPayload.ViewerCreated...)
 	} else {
-		printMessage("  You have no open pull requests")
+		printMessage(out, "  You have no open pull requests")
 	}
-	fmt.Println()
+	fmt.Fprintln(out)
 
-	printHeader("Requesting a code review from you")
+	printHeader(out, "Requesting a code review from you")
 	if len(prPayload.ReviewRequested) > 0 {
-		printPrs(prPayload.ReviewRequested...)
+		printPrs(out, prPayload.ReviewRequested...)
 	} else {
-		printMessage("  You have no pull requests to review")
+		printMessage(out, "  You have no pull requests to review")
 	}
-	fmt.Println()
+	fmt.Fprintln(out)
 
 	return nil
 }
@@ -330,15 +333,15 @@ func prCheckout(cmd *cobra.Command, args []string) error {
 	return nil
 }
 
-func printPrs(prs ...api.PullRequest) {
+func printPrs(w io.Writer, prs ...api.PullRequest) {
 	for _, pr := range prs {
 		prNumber := fmt.Sprintf("#%d", pr.Number)
-		fmt.Printf("  %s  %s %s", utils.Yellow(prNumber), truncate(50, pr.Title), utils.Cyan("["+pr.HeadLabel()+"]"))
+		fmt.Fprintf(w, "  %s  %s %s", utils.Yellow(prNumber), truncate(50, pr.Title), utils.Cyan("["+pr.HeadLabel()+"]"))
 
 		checks := pr.ChecksStatus()
 		reviews := pr.ReviewStatus()
 		if checks.Total > 0 || reviews.ChangesRequested || reviews.Approved {
-			fmt.Printf("\n  ")
+			fmt.Fprintf(w, "\n  ")
 		}
 
 		if checks.Total > 0 {
@@ -354,27 +357,27 @@ func printPrs(prs ...api.PullRequest) {
 			} else if checks.Passing == checks.Total {
 				summary = utils.Green("Checks passing")
 			}
-			fmt.Printf(" - %s", summary)
+			fmt.Fprintf(w, " - %s", summary)
 		}
 
 		if reviews.ChangesRequested {
-			fmt.Printf(" - %s", utils.Red("changes requested"))
+			fmt.Fprintf(w, " - %s", utils.Red("changes requested"))
 		} else if reviews.ReviewRequired {
-			fmt.Printf(" - %s", utils.Yellow("review required"))
+			fmt.Fprintf(w, " - %s", utils.Yellow("review required"))
 		} else if reviews.Approved {
-			fmt.Printf(" - %s", utils.Green("approved"))
+			fmt.Fprintf(w, " - %s", utils.Green("approved"))
 		}
 
-		fmt.Printf("\n")
+		fmt.Fprint(w, "\n")
 	}
 }
 
-func printHeader(s string) {
-	fmt.Println(utils.Bold(s))
+func printHeader(w io.Writer, s string) {
+	fmt.Fprintln(w, utils.Bold(s))
 }
 
-func printMessage(s string) {
-	fmt.Println(utils.Gray(s))
+func printMessage(w io.Writer, s string) {
+	fmt.Fprintln(w, utils.Gray(s))
 }
 
 func truncate(maxLength int, title string) string {

command/root.go

@@ -2,11 +2,13 @@ package command
 
 import (
 	"fmt"
+	"io"
 	"os"
 	"strings"
 
 	"github.com/github/gh-cli/api"
 	"github.com/github/gh-cli/context"
+	"github.com/github/gh-cli/utils"
 
 	"github.com/spf13/cobra"
 )
@@ -93,3 +95,11 @@ var apiClientForContext = func(ctx context.Context) (*api.Client, error) {
 	}
 	return api.NewClient(opts...), nil
 }
+
+func colorableOut(cmd *cobra.Command) io.Writer {
+	out := cmd.OutOrStdout()
+	if outFile, isFile := out.(*os.File); isFile {
+		return utils.NewColorable(outFile)
+	}
+	return out
+}

utils/color.go

@@ -1,11 +1,19 @@
 package utils
 
 import (
+	"io"
+	"os"
+
+	"github.com/mattn/go-colorable"
 	"github.com/mattn/go-isatty"
 	"github.com/mgutz/ansi"
-	"os"
 )
 
+// NewColorable returns an output stream that handles ANSI color sequences on Windows
+func NewColorable(f *os.File) io.Writer {
+	return colorable.NewColorable(f)
+}
+
 func makeColorFunc(color string) func(string) string {
 	return func(arg string) string {
 		output := arg

utils/table_printer.go

@@ -8,7 +8,6 @@ import (
 	"strconv"
 	"strings"
 
-	"github.com/mattn/go-colorable"
 	"github.com/mattn/go-isatty"
 	"golang.org/x/crypto/ssh/terminal"
 )
@@ -37,7 +36,7 @@ func NewTablePrinter(w io.Writer) TablePrinter {
 				}
 			}
 			return &ttyTablePrinter{
-				out:      colorable.NewColorable(outFile),
+				out:      NewColorable(outFile),
 				maxWidth: ttyWidth,
 			}
 		}