From 4403faa63dfaae84cadd59ec783f9fdf158a313d Mon Sep 17 00:00:00 2001
From: GBDixonAlex <alex.dixon@sony.com>
Date: Fri, 12 Jul 2024 15:44:19 +0100
Subject: [PATCH] - add env var support evaluated in vars

---
 jsn.py    | 18 ++++++++++++++----
 readme.md |  5 ++++-
 2 files changed, 18 insertions(+), 5 deletions(-)

diff --git a/jsn.py b/jsn.py
index bc3d7a3..4b3a66f 100644
--- a/jsn.py
+++ b/jsn.py
@@ -610,8 +610,16 @@ def vars_in_string(string):
         else:
             break
     return variables
-            
-    
+
+
+# replaces a ${var} with system environment var if it exists
+def get_env_var(var_name):
+    if var_name in os.environ.keys():
+        return os.environ[var_name]
+    print_error("[jsn error] undefined variable '" + var_name + "'")
+    sys.exit(1)
+
+
 # resolves "${var}" into a typed value or a token pasted string, handle multiple vars within strings or arrays
 def resolve_vars(value, vars):
     value_string = str(value)
@@ -637,8 +645,10 @@ def resolve_vars(value, vars):
                 else:
                     return vars[var_name]
         else:
-            print_error("[jsn error] undefined variable '" + var_name + "'")
-            sys.exit(1)
+            ev = get_env_var(var_name)
+            value = value.replace(v, ev)
+            if len(vv) == count+1:
+                return value
         count += 1
     return None
 
diff --git a/readme.md b/readme.md
index c352966..c1a6cdd 100644
--- a/readme.md
+++ b/readme.md
@@ -150,7 +150,10 @@ import test.jsn
         // you can use special variables:
         // inject the current script directory into a string
         // - this is the directory name of the file this variable is used in
-        script_directory: "${script_dir}" 
+        script_directory: "${script_dir}"
+
+        // env vars can also be injected, if no variable is found in the script jsn will fallback to check if an env var exists
+        env_vars: ${OS_ENV_VAR}
         
         // subobjects can be merged and inherited recursively see ** inheritence(jsn)
         base: "foo"