bug: Environment variable with common prefix returns incorrect value in init_by_lua

[ChuanFF]

Current Behavior

Description:
When reading environment variables in the init_by_lua phase, if two variables share a common prefix (e.g., KUBERNETES_CLIENT_TOKEN and KUBERNETES_CLIENT_TOKEN_FILE), the value of the shorter-named variable may be erroneously returned when the longer-named one is requested. The issue appears to be sensitive to the order in which the variables are defined in the configuration.

Expected Behavior

Expected behavior:
os.getenv("KUBERNETES_CLIENT_TOKEN_FILE") should always return the value of the environment variable named exactly KUBERNETES_CLIENT_TOKEN_FILE, regardless of the definition order of the env directives.

Error Logs

No response

Steps to Reproduce

Steps to reproduce:

1. Create a test configuration similar to t/kubernetes/discovery/kubernetes2.t that defines two environment variables with a common prefix, e.g.:

   env KUBERNETES_CLIENT_TOKEN=some-token;
   env KUBERNETES_CLIENT_TOKEN_FILE=/path/to/token;
   

2. In init_by_lua, attempt to read KUBERNETES_CLIENT_TOKEN_FILE using os.getenv("KUBERNETES_CLIENT_TOKEN_FILE").
3. Observe that the returned value is some-token (the value of the shorter variable) instead of /path/to/token.
4. Swap the order of the two env directives so that the longer name (KUBERNETES_CLIENT_TOKEN_FILE) appears first:

   env KUBERNETES_CLIENT_TOKEN_FILE=/path/to/token;
   env KUBERNETES_CLIENT_TOKEN=some-token;
   

5. In init_by_lua, again read KUBERNETES_CLIENT_TOKEN_FILE – this time it returns the correct value /path/to/token.

Environment

master branch

[Baoyuantop]

https://github.com/Baoyuantop/apisix/actions/runs/22709179590/job/65842804103?pr=4#step:17:418

I wrote a test and it ran in my repository. Could you please help confirm if this matches the problem you described? @ChuanFF

[ChuanFF]

@Baoyuantop
bug is in init rather than worker init:

=== TEST 3: init phase os.getenv prefix collision
--- main_config
env KUBERNETES_CLIENT_TOKEN=some-token;
env KUBERNETES_CLIENT_TOKEN_FILE=/path/to/token;
--- extra_init_by_lua
        ngx.shared["test"]:set("iw_token", os.getenv("KUBERNETES_CLIENT_TOKEN") or "NIL")
        ngx.shared["test"]:set("iw_token_file", os.getenv("KUBERNETES_CLIENT_TOKEN_FILE") or "NIL")
--- config
    location /t {
        content_by_lua_block {
            ngx.say("TOKEN=", ngx.shared["test"]:get("iw_token"))
            ngx.say("TOKEN_FILE=", ngx.shared["test"]:get("iw_token_file"))
        }
    }
--- request
GET /t
--- response_body
TOKEN=some-token
TOKEN_FILE=/path/to/token

[Baoyuantop]

https://github.com/Baoyuantop/apisix/actions/runs/22742229359/job/65958008618?pr=4#step:17:766

It did fail after the adjustment.