From cf19735324e2473d60dd1555293605c9079eb84c Mon Sep 17 00:00:00 2001
From: Olaf Alders <olaf@wundersolutions.com>
Date: Mon, 27 Jan 2025 15:32:46 -0500
Subject: [PATCH 1/2] Add bin/test-everything

---
 bin/test-everything | 7 +++++++
 1 file changed, 7 insertions(+)
 create mode 100755 bin/test-everything

diff --git a/bin/test-everything b/bin/test-everything
new file mode 100755
index 0000000..003a04f
--- /dev/null
+++ b/bin/test-everything
@@ -0,0 +1,7 @@
+#!/bin/bash
+
+set -eux -o pipefail
+
+go test -v ./...
+go build
+bats test

From 7fffda9847b238beb4f670e8a77ab7cdc60d6b79 Mon Sep 17 00:00:00 2001
From: Olaf Alders <olaf@wundersolutions.com>
Date: Mon, 27 Jan 2025 15:11:04 -0500
Subject: [PATCH 2/2] Allow for var comparisons with empty strings

---
 CHANGELOG.md  |  4 ++++
 README.md     | 27 +++++++++++++++++++++++++++
 api.go        |  8 +++++++-
 test/var.bats | 49 +++++++++++++++++++++++++++++++++++++++++++++++++
 var.go        |  4 ++--
 5 files changed, 89 insertions(+), 3 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 61f2bb0..6d06661 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,9 @@
 # Changes
 
+- Allow for empty string comparisons via "eq" and "ne" in "is var". e.g.
+  - is var FOO eq ""
+  - is var FOO ne ""
+
 ## 0.6.0 - 2025-01-20
 
 - Add var subcommand
diff --git a/README.md b/README.md
index a9f2ed5..9be73a4 100644
--- a/README.md
+++ b/README.md
@@ -767,6 +767,19 @@ Check if environment variables are set, unset or contain a specific value.
 
 ```bash
 is var EDITOR set && is var EDITOR like vim
+
+is var EDITOR set && is var EDITOR eq ""
+```
+
+`is var` can only operate on environment variables which are available in its
+environment. This means that you may need to export some variables before you
+can invoke `is var`. For example, if you have created a variable in the current
+script, it should be exported before `is var` is used.
+
+```shell
+SLOW_HORSE=rivercartwright
+export SLOW_HORSE
+is var SLOW_HORSE like cart && echo "blue shirt, white tee"
 ```
 
 #### set
@@ -796,6 +809,20 @@ Supported comparisons are:
 - `like`
 - `unlike`
 
+Both `eq` and `ne` allow for comparisons with an empty string:
+
+```shell
+SET_BUT_EMPTY=
+export SET_BUT_EMPTY
+
+is var SET_BUT_EMPTY set && is var SET_BUT_EMPTY eq ""
+
+NOT_EMPTY=lebowski
+export NOT_EMPTY
+
+is var NOT_EMPTY set && is var NOT_EMPTY ne ""
+```
+
 ##### --compare
 
 Optional argument to command. Defaults to `optimistic`. Because comparisons
diff --git a/api.go b/api.go
index 69a18c2..d93ecc4 100644
--- a/api.go
+++ b/api.go
@@ -82,8 +82,14 @@ type VarCmd struct {
 	Compare string `default:"optimistic" enum:"float,integer,string,version,optimistic" help:"[float|integer|string|version|optimistic]"`
 }
 
+// Allow for the following:
+//
+// is var EDITOR eq ""
+// is var EDITOR ne ""
+//
+// .
 func (r *VarCmd) Validate() error {
-	if r.Op != "set" && r.Op != "unset" && r.Val == "" {
+	if r.Op != "set" && r.Op != "unset" && r.Op != "eq" && r.Op != "ne" && r.Val == "" {
 		return fmt.Errorf("missing required argument: val")
 	}
 	return nil
diff --git a/test/var.bats b/test/var.bats
index f138473..2ae0ba2 100755
--- a/test/var.bats
+++ b/test/var.bats
@@ -94,3 +94,52 @@ teardown() {
   [ "$status" -eq 1 ]
   [[ "$output" == *"wanted result must be an integer"* ]]
 }
+
+@test "is var EMPTY_VAR eq '' should pass" {
+  export EMPTY_VAR=""
+  run ./is var EMPTY_VAR eq ""
+  [ "$status" -eq 0 ]
+}
+
+# we can't determine the difference between eq "" and eq with no trailing arg
+@test "'is var EMPTY_VAR eq' should pass" {
+  export EMPTY_VAR=""
+  run ./is var EMPTY_VAR eq
+  [ "$status" -eq 0 ]
+}
+
+@test "is var EMPTY_VAR eq \"\" should fail" {
+  run ./is var EMPTY_VAR eq ""
+  [ "$status" -eq 1 ]
+}
+
+@test "is var EMPTY_VAR set should pass" {
+  export EMPTY_VAR=""
+  run ./is var EMPTY_VAR set
+  [ "$status" -eq 0 ]
+}
+
+@test "is var EMPTY_VAR unset should fail" {
+  export EMPTY_VAR=""
+  run ./is var EMPTY_VAR unset
+  [ "$status" -eq 1 ]
+}
+
+@test "is var EMPTY_VAR ne '' should fail" {
+  export EMPTY_VAR=""
+  run ./is var EMPTY_VAR ne ""
+  [ "$status" -eq 1 ]
+}
+
+# we can't determine the difference between ne "" and ne with no trailing arg
+@test "is var EMPTY_VAR ne should fail" {
+  export EMPTY_VAR=""
+  run ./is var EMPTY_VAR ne
+  [ "$status" -eq 1 ]
+}
+
+@test "is var EMPTY_VAR ne 'non-empty' should pass" {
+  export EMPTY_VAR=""
+  run ./is var EMPTY_VAR ne "non-empty"
+  [ "$status" -eq 0 ]
+}
diff --git a/var.go b/var.go
index bc89d1f..a12aedb 100644
--- a/var.go
+++ b/var.go
@@ -2,7 +2,7 @@
 package main
 
 import (
-	"errors"
+	"fmt"
 	"os"
 
 	"github.com/oalders/is/types"
@@ -27,7 +27,7 @@ func (r *VarCmd) Run(ctx *types.Context) error {
 	default:
 		val, exists := os.LookupEnv(r.Name)
 		if !exists {
-			return errors.New("environment variable not set")
+			return fmt.Errorf("environment variable %s is not set", r.Name)
 		}
 		return compareOutput(ctx, r.Compare, r.Op, val, r.Val)
 	}