Support default values in ${env}

Author: ericdallo

CHANGELOG.md

@@ -3,6 +3,7 @@
 ## Unreleased
 
 - Support `${classapath:path/to/eca/classpath/file}` in dynamic string parse.
+- Support default env values in `${env:MY_ENV:default-value}`.
 - Deprecate configs: 
   - `systemPromptFile` in favor of `systemPrompt` using `${file:...}` or `${classpath:...}`
 

docs/configuration.md

@@ -475,9 +475,7 @@ To configure, add your OTLP collector config via `:otlp` map following [otlp aut
         providers?: {[key: string]: {
             api?: 'openai-responses' | 'openai-chat' | 'anthropic';
             url?: string;
-            urlEnv?: string;
             key?: string; // when provider supports api key.
-            keyEnv?: string;
             keyRc?: string; // credential file lookup in format [login@]machine[:port]
             completionUrlRelativePath?: string;
             thinkTagStart?: string;

src/eca/config.clj

@@ -84,8 +84,7 @@
                          :requiresAuth? true
                          :models {"gemini-2.0-flash" {}
                                   "gemini-2.5-pro" {}}}
-               "ollama" {:url "http://localhost:11434"
-                         :urlEnv "OLLAMA_API_URL"}}
+               "ollama" {:url "${env:OLLAMA_API_URL:http://localhost:11434}"}}
    :defaultBehavior "agent"
    :behavior {"agent" {:systemPrompt "${classpath:prompts/agent_behavior.md}"
                        :disabledTools ["preview_file_change"]}
@@ -149,14 +148,14 @@
 
 (defn ^:private parse-dynamic-string
   "Given a string and a current working directory, look for patterns replacing its content:
-  - `${env:SOME-ENV}`: Replace with a env
+  - `${env:SOME-ENV:default-value}`: Replace with a env falling back to a optional default value
   - `${file:/some/path}`: Replace with a file content checking from cwd if relative
   - `${classpath:path/to/file}`: Replace with a file content found checking classpath"
   [s cwd]
   (some-> s
-          (string/replace #"\$\{env:([^}]+)\}"
-                          (fn [[_match env-var]]
-                            (or (get-env env-var) "")))
+          (string/replace #"\$\{env:([^:}]+)(?::([^}]*))?\}"
+                          (fn [[_match env-var default-value]]
+                            (or (get-env env-var) default-value "")))
           (string/replace #"\$\{file:([^}]+)\}"
                           (fn [[_match file-path]]
                             (try

test/eca/config_test.clj

@@ -209,6 +209,43 @@
       (is (= "" (#'config/parse-dynamic-string "${env:UNDEFINED_VAR}" "/tmp")))
       (is (= "prefix  suffix" (#'config/parse-dynamic-string "prefix ${env:UNDEFINED_VAR} suffix" "/tmp")))))
 
+  (testing "replaces undefined env var with default value"
+    (with-redefs [config/get-env (constantly nil)]
+      (is (= "default-value" (#'config/parse-dynamic-string "${env:UNDEFINED_VAR:default-value}" "/tmp")))
+      (is (= "http://localhost:11434" (#'config/parse-dynamic-string "${env:OLLAMA_API_URL:http://localhost:11434}" "/tmp")))
+      (is (= "prefix default-value suffix" (#'config/parse-dynamic-string "prefix ${env:UNDEFINED_VAR:default-value} suffix" "/tmp")))))
+
+  (testing "uses env var value when set, ignoring default"
+    (with-redefs [config/get-env (fn [env-var]
+                                   (case env-var
+                                     "TEST_VAR" "actual-value"
+                                     "OLLAMA_API_URL" "http://custom:8080"
+                                     nil))]
+      (is (= "actual-value" (#'config/parse-dynamic-string "${env:TEST_VAR:default-value}" "/tmp")))
+      (is (= "http://custom:8080" (#'config/parse-dynamic-string "${env:OLLAMA_API_URL:http://localhost:11434}" "/tmp")))))
+
+  (testing "handles default values with special characters"
+    (with-redefs [config/get-env (constantly nil)]
+      (is (= "http://localhost:11434/api" (#'config/parse-dynamic-string "${env:API_URL:http://localhost:11434/api}" "/tmp")))
+      (is (= "value-with-dashes" (#'config/parse-dynamic-string "${env:VAR:value-with-dashes}" "/tmp")))
+      (is (= "value_with_underscores" (#'config/parse-dynamic-string "${env:VAR:value_with_underscores}" "/tmp")))
+      (is (= "/path/to/file" (#'config/parse-dynamic-string "${env:VAR:/path/to/file}" "/tmp")))))
+
+  (testing "handles empty default value"
+    (with-redefs [config/get-env (constantly nil)]
+      (is (= "" (#'config/parse-dynamic-string "${env:UNDEFINED_VAR:}" "/tmp")))
+      (is (= "prefix  suffix" (#'config/parse-dynamic-string "prefix ${env:UNDEFINED_VAR:} suffix" "/tmp")))))
+
+  (testing "handles multiple env vars with mixed default values"
+    (with-redefs [config/get-env (fn [env-var]
+                                   (case env-var
+                                     "DEFINED_VAR" "defined"
+                                     nil))]
+      (is (= "defined and default-value"
+             (#'config/parse-dynamic-string "${env:DEFINED_VAR:fallback1} and ${env:UNDEFINED_VAR:default-value}" "/tmp")))
+      (is (= "defined and "
+             (#'config/parse-dynamic-string "${env:DEFINED_VAR} and ${env:UNDEFINED_VAR}" "/tmp")))))
+
   (testing "replaces file pattern with file content - absolute path"
     (with-redefs [fs/absolute? (fn [path] (= path "/absolute/file.txt"))
                   slurp (fn [path]