when updating config due to version change, block command on it

[joeshaw]

Normally the CLI updates the config in the background for subsequent
executions. However, if the version changes we need to get the updated
config in place before we execute the command.

[joeshaw]

An alternative approach I explored was having the fastly update command execute the new binary as a test, and rely on it writing out the config because the versions don't match.

diff --git pkg/commands/update/root.go pkg/commands/update/root.go
index d832861..a434f82 100644
--- pkg/commands/update/root.go
+++ pkg/commands/update/root.go
@@ -5,6 +5,7 @@ import (
        "fmt"
        "io"
        "os"
+       "os/exec"
        "path/filepath"

        "github.com/fastly/cli/pkg/cmd"
@@ -122,6 +123,15 @@ func (c *RootCommand) Exec(in io.Reader, out io.Writer) error {
                }
        }

+       progress.Step("Testing binary...")
+       if err := exec.Command(currentPath, "version").Run(); err != nil {
+               c.Globals.ErrLog.AddWithContext(err, map[string]interface{}{
+                       "Executable": currentPath,
+               })
+               progress.Fail()
+               return fmt.Errorf("error running new binary: %w", err)
+       }
+
        progress.Done()

        text.Success(out, "Updated %s to %s.", currentPath, latest)

The problem with this is that there's a race because the old code could write out the config file after the new code does because it's done in the background.

[Integralist]

LGTM. I think for these occasions (i.e. when updating to a new CLI version) it's OK to block for the config 👍🏻