fix: provide empty string to 0 length process environment variables (#5679)

* fix: provide empty string to len 0 process env vars

For process loaded env vars, its a bug to give them the literal value '""'
if the provided length is 0.

* fix: add test and remove unneeded branch

Removes the redundant branch for empty env vars and adds a test for the
process specific case.

* fix: remove empty_string_value

Removes the constant in favor of using the empty values or passing the
literal "".

* style: format env.test.ts

1 files changed, 10 insertions, 0 deletions

diff --git a/test/cli/run/env.test.ts b/test/cli/run/env.test.ts
index 3ed300477..1c2d51e8e 100644
--- a/test/cli/run/env.test.ts
+++ b/test/cli/run/env.test.ts
@@ -385,6 +385,16 @@ test(".env with zero length strings", () => {
   expect(stdout).toBe("||0|0");
 });
 
+test("process with zero length environment variable", () => {
+  const dir = tempDirWithFiles("process-issue-zerolength", {
+    "index.ts": "console.log(`'${process.env.TEST_ENV_VAR}'`);",
+  });
+  const { stdout } = bunRun(`${dir}/index.ts`, {
+    TEST_ENV_VAR: "",
+  });
+  expect(stdout).toBe("''");
+});
+
 test(".env in a folder doesn't throw an error", () => {
   const dir = tempDirWithFiles("dotenv-issue-3670", {
     ".env": {