fix: Update workspace list implementation to tolerate warnings present in stdout output

tfexec/workspace_list.go

@@ -5,6 +5,7 @@ package tfexec
 
 import (
 	"context"
+	"net/url"
 	"os/exec"
 	"strings"
 )
@@ -72,12 +73,28 @@ func parseWorkspaceList(stdout string) ([]string, string) {
 	for _, line := range lines {
 		line = strings.TrimSpace(line)
 		if line == "" {
+			// results from successive newlines in stdout string; ignore
 			continue
 		}
+
 		if strings.HasPrefix(line, currentWorkspacePrefix) {
 			line = strings.TrimPrefix(line, currentWorkspacePrefix)
 			current = line
 		}
+
+		if line != url.PathEscape(line) {
+			// If a line isn't URL-escaped then it's not a valid workspace name.
+			// If we're encountering a processed line string that isn't a valid workspace name it's
+			// almost certainly due to a warning being sent to stdout after the workspace commands
+			// were migrated from using cli.Ui to view.View, which causes warnings to begin being sent to
+			// stdout instead of stderr.
+			// See: https://github.com/hashicorp/terraform/blob/9fb1177c3566c247c72e6c36ca219463c4b6be2b/internal/command/workspace_command.go#L44-L52
+			//
+			// tl;dr this line isn't a workspace name, so lets skip and see if there is a list of
+			// workspaces later in the output, under any warning text.
+			continue
+		}
+
 		workspaces = append(workspaces, line)
 	}
 

tfexec/workspace_list_test.go

@@ -94,6 +94,36 @@ func TestParseWorkspaceList(t *testing.T) {
 			"foo",
 			"  default\r\n* foo\r\n\r\n",
 		},
+		// warning about no workspaces being present is set to stdout and
+		// should not be parsed as a list.
+		{
+			[]string{},
+			"",
+			`
+Warning: Terraform cannot find any existing workspaces.
+
+The "default" workspace is selected in your working directory. You can create
+this workspace by running "terraform init", by using the "terraform workspace
+new" subcommand or by including the "-or-create" flag with the "terraform
+workspace select" subcommand.
+
+`,
+		},
+		// warning present alongside a list of workspaces.
+		{
+			[]string{"default", "foo", "bar"},
+			"foo",
+			`
+Warning: This warning is part of a test!
+
+This warning doesn't exist in Terraform core, but we're seeing if it can be
+ignored while parsing the list below:
+
+  default
+* foo
+  bar
+`,
+		},
 	} {
 		t.Run(fmt.Sprintf("%d", i), func(t *testing.T) {
 			actualList, actualCurrent := parseWorkspaceList(c.stdout)