Add ${plugin:root} dynamic interpolation for plugin config, hooks, commands, and rules

Author: zikajk

CHANGELOG.md

@@ -3,6 +3,7 @@
 ## Unreleased
 
 - Add configurable skill paths and recursive directory loading for configured rules, commands, and skills; local skills are also discovered from `.agents/skills`. #423
+- Add `${plugin:root}` dynamic interpolation for plugin-provided config, hooks, commands, and rules.
 
 ## 0.130.0
 

src/eca/features/commands.clj

@@ -14,6 +14,7 @@
    [eca.features.skills :as f.skills]
    [eca.features.tools.mcp :as f.mcp]
    [eca.features.tools.util :as tools.util]
+   [eca.interpolation :as interpolation]
    [eca.llm-api :as llm-api]
    [eca.llm-util :as llm-util]
    [eca.messenger :as messenger]
@@ -56,13 +57,14 @@
     :else [path]))
 
 (defn ^:private command-file->command [type file opts]
-  (let [base (normalize-command-name file)]
+  (let [base (normalize-command-name file)
+        content (interpolation/replace-dynamic-strings (slurp (str file)) (str (fs/parent file)) nil)]
     (cond-> {:name (if-let [plugin (:plugin opts)]
                      (prefixed-command-name plugin base)
                      base)
              :path (str (fs/canonicalize file))
              :type type
-             :content (slurp (str file))}
+             :content content}
       (:plugin opts) (assoc :plugin (:plugin opts)))))
 
 (defn ^:private global-file-commands []

src/eca/features/plugins.clj

@@ -14,6 +14,7 @@
    [eca.cache :as cache]
    [eca.config :as config]
    [eca.features.agents :as agents]
+   [eca.interpolation :as interpolation]
    [eca.logger :as logger]
    [eca.shared :as shared]))
 
@@ -149,37 +150,43 @@
 ;; -- Component readers --
 
 (defn ^:private read-hooks
-  "Reads hooks/hooks.json from a plugin directory. Expects ECA native hook format."
+  "Reads hooks/hooks.json from a plugin directory. Expects ECA native hook format.
+   Applies dynamic string interpolation after JSON parsing."
   [^java.io.File plugin-dir]
   (let [hooks-file (io/file plugin-dir "hooks" "hooks.json")]
     (when (fs/exists? hooks-file)
       (try
-        (json/parse-string (slurp hooks-file) true)
+        (-> (json/parse-string (slurp hooks-file) true)
+            (interpolation/replace-dynamic-strings-in-data (str (fs/parent hooks-file)) nil))
         (catch Exception e
           (logger/warn logger-tag "Failed to parse hooks.json:" (str hooks-file)
                        (.getMessage e))
           nil)))))
 
 (defn ^:private read-mcp-servers
-  "Reads .mcp.json from a plugin directory and returns mcpServers map."
+  "Reads .mcp.json from a plugin directory and returns mcpServers map.
+   Applies dynamic string interpolation after JSON parsing."
   [^java.io.File plugin-dir]
   (let [mcp-file (io/file plugin-dir ".mcp.json")]
     (when (fs/exists? mcp-file)
       (try
-        (let [content (json/parse-string (slurp mcp-file) true)]
+        (let [content (-> (json/parse-string (slurp mcp-file) true)
+                          (interpolation/replace-dynamic-strings-in-data (str plugin-dir) nil))]
           (:mcpServers content))
         (catch Exception e
           (logger/warn logger-tag "Failed to parse .mcp.json:" (str mcp-file)
                        (.getMessage e))
           nil)))))
 
 (defn ^:private read-eca-config
-  "Reads eca.json from a plugin directory for arbitrary ECA config overrides."
+  "Reads eca.json from a plugin directory for arbitrary ECA config overrides.
+   Applies dynamic string interpolation after JSON parsing."
   [^java.io.File plugin-dir]
   (let [config-file (io/file plugin-dir "eca.json")]
     (when (fs/exists? config-file)
       (try
-        (json/parse-string (slurp config-file) true)
+        (-> (json/parse-string (slurp config-file) true)
+            (interpolation/replace-dynamic-strings-in-data (str plugin-dir) nil))
         (catch Exception e
           (logger/warn logger-tag "Failed to parse eca.json:" (str config-file)
                        (.getMessage e))
@@ -328,6 +335,7 @@
                                               "in" (str source-dir)))
                                plugin-dir)]
                  (do (logger/info logger-tag "Loading plugin:" plugin-name "from" source-name)
+                     (interpolation/register-plugin-dir! (str plugin-dir))
                      (discover-components plugin-dir plugin-name))))]
           (merge-components components))))))
 

src/eca/features/rules.clj

@@ -4,6 +4,7 @@
    [clojure.string :as string]
    [babashka.fs :as fs]
    [eca.config :as config]
+   [eca.interpolation :as interpolation]
    [eca.logger :as logger]
    [eca.shared :as shared :refer [assoc-some]])
   (:import
@@ -136,10 +137,11 @@
     :else [path]))
 
 (defn ^:private rule-file [type file opts]
-  (rule-file->rule type
-                   (fs/canonicalize file)
-                   (slurp (str file))
-                   {:workspace-root (:workspace-root opts)}))
+  (let [content (interpolation/replace-dynamic-strings (slurp (str file)) (str (fs/parent file)) nil)]
+    (rule-file->rule type
+                     (fs/canonicalize file)
+                     content
+                     {:workspace-root (:workspace-root opts)})))
 
 (defn ^:private global-file-rules []
   (let [xdg-config-home (or (config/get-env "XDG_CONFIG_HOME")

src/eca/interpolation.clj

@@ -18,13 +18,43 @@
    [babashka.process :as p]
    [clojure.java.io :as io]
    [clojure.string :as string]
+   [clojure.walk :as walk]
    [eca.logger :as logger]
+   [eca.shared :as shared]
    [eca.secrets :as secrets]))
 
 (set! *warn-on-reflection* true)
 
 (def ^:private logger-tag "[INTERPOLATION]")
 
+(defonce ^:private plugin-dirs*
+  (atom #{}))
+
+(defn register-plugin-dir!
+  "Registers a plugin directory path for `${plugin:root}` resolution.
+   Called by the plugin system when loading plugins."
+  [^String dir]
+  (swap! plugin-dirs* conj (shared/normalize-path dir)))
+
+(defn reset-plugin-dirs!
+  "Clears all registered plugin directories. Test helper."
+  []
+  (reset! plugin-dirs* #{}))
+
+(defn ^:private matching-plugin-dir
+  "Given a file path (the cwd of the file being interpolated), returns the
+   plugin directory that contains it, or nil if the file is not inside any
+   registered plugin directory."
+  [^String file-path]
+  (when (and file-path (seq @plugin-dirs*))
+    (let [normalized (shared/normalize-path file-path)
+          separator (System/getProperty "file.separator")]
+      (->> @plugin-dirs*
+           (some (fn [dir]
+                   (when (or (= normalized dir)
+                             (string/starts-with? normalized (str dir separator)))
+                     dir)))))))
+
 (defn get-env [env] (System/getenv env))
 
 (def ^:private cmd-default-timeout-ms 30000)
@@ -206,9 +236,17 @@
   - `${file:/some/path}`: Replace with a file content checking from cwd if relative
   - `${classpath:path/to/file}`: Replace with a file content found checking classpath
   - `${netrc:api.provider.com}`: Replace with the content from Unix net RC [credential files](https://eca.dev/config/models/#credential-file-authentication)
-  - `${cmd:some command}`: Replace with the trimmed stdout of an arbitrary shell command"
+  - `${cmd:some command}`: Replace with the trimmed stdout of an arbitrary shell command
+  - `${plugin:root}`: Replace with the absolute path of the plugin directory containing
+    the file being interpolated. Resolved by checking `cwd` against registered plugin dirs.
+    If the file is not inside a plugin, the placeholder is replaced with an empty string."
   [s cwd config]
   (some-> s
+          (string/replace #"\$\{plugin:root\}"
+                          (fn [_match]
+                            (or (matching-plugin-dir (some-> cwd str))
+                                (do (logger/warn logger-tag "No plugin directory found for ${plugin:root} in:" (str cwd))
+                                    ""))))
           (string/replace #"\$\{env:([^:}]+)(?::([^}]*))?\}"
                           (fn [[_match env-var default-value]]
                             (or (get-env env-var) default-value "")))
@@ -245,3 +283,13 @@
                               (catch Exception e
                                 (logger/warn logger-tag "Error executing cmd:" (.getMessage e))
                                 ""))))))
+
+(defn replace-dynamic-strings-in-data
+  "Walks data and applies dynamic string interpolation to every string value."
+  [data cwd config]
+  (walk/postwalk
+   (fn [x]
+     (if (string? x)
+       (replace-dynamic-strings x cwd config)
+       x))
+   data))

test/eca/features/plugins_test.clj

@@ -2,12 +2,23 @@
   (:require
    [babashka.fs :as fs]
    [cheshire.core :as json]
-   [clojure.test :refer [deftest is testing]]
+   [clojure.test :refer [deftest is testing use-fixtures]]
    [eca.config :as config]
+   [eca.features.commands :as commands]
    [eca.features.plugins :as plugins]
+   [eca.features.rules :as rules]
+   [eca.interpolation :as interpolation]
    [matcher-combinators.matchers :as m]
    [matcher-combinators.test :refer [match?]]))
 
+(use-fixtures :each
+  (fn [t]
+    (interpolation/reset-plugin-dirs!)
+    (try
+      (t)
+      (finally
+        (interpolation/reset-plugin-dirs!)))))
+
 (deftest sanitize-source-url-test
   (testing "HTTPS URL"
     (is (= "github.com-my-org-my-plugins"
@@ -219,6 +230,61 @@
       (finally
         (fs/delete-tree tmp-dir)))))
 
+(deftest plugin-root-interpolation-test
+  (let [tmp-dir (fs/create-temp-dir)]
+    (try
+      (let [source-dir (fs/file tmp-dir "repo")
+            plugin-dir (fs/file source-dir "plugins" "test" "demo")
+            secret "line \"quoted\"\nbackslash \\ ok"]
+        (fs/create-dirs (fs/file source-dir ".eca-plugin"))
+        (fs/create-dirs (fs/file plugin-dir "hooks"))
+        (fs/create-dirs (fs/file plugin-dir "commands"))
+        (fs/create-dirs (fs/file plugin-dir "rules"))
+        (spit (fs/file source-dir ".eca-plugin" "marketplace.json")
+              (json/generate-string
+               {:plugins [{:name "demo"
+                           :description "Demo"
+                           :source "./plugins/test/demo"}]}))
+        (spit (fs/file plugin-dir "secret.txt") secret)
+        (spit (fs/file plugin-dir ".mcp.json")
+              (json/generate-string
+               {:mcpServers {"local" {:command "${plugin:root}/bin/server"}}}))
+        (spit (fs/file plugin-dir "eca.json")
+              (json/generate-string
+               {:pluginRoot "${plugin:root}"
+                :quotedSecret "${file:secret.txt}"}))
+        (spit (fs/file plugin-dir "hooks" "hooks.json")
+              (json/generate-string
+               {:PostToolUse [{:hooks [{:type "command"
+                                         :command "node ${plugin:root}/hooks/check.js"}]}]}))
+        (spit (fs/file plugin-dir "commands" "where.md")
+              "Plugin command: ${plugin:root}")
+        (spit (fs/file plugin-dir "rules" "where.md")
+              "Plugin rule: ${plugin:root}")
+        (let [plugin-root (str (fs/canonicalize plugin-dir))
+              result (plugins/resolve-all!
+                      {"local" {:source (str source-dir)}
+                       "install" ["demo"]})]
+          (is (= (str plugin-root "/bin/server")
+                 (get-in result [:config-fragment :mcpServers :local :command])))
+          (is (= plugin-root
+                 (get-in result [:config-fragment :pluginRoot])))
+          (is (= secret
+                 (get-in result [:config-fragment :quotedSecret])))
+          (is (= (str "node " plugin-root "/hooks/check.js")
+                 (get-in result [:config-fragment :hooks :PostToolUse 0 :hooks 0 :command])))
+          (let [loaded-commands (vec (#'commands/custom-commands
+                                      {:pureConfig true
+                                       :commands (:commands result)}
+                                      []))]
+            (is (= [(str "Plugin command: " plugin-root)]
+                   (mapv :content loaded-commands))))
+          (let [loaded-rules (vec (#'rules/config-rules {:rules (:rules result)} []))]
+            (is (= [(str "Plugin rule: " plugin-root)]
+                   (mapv :content loaded-rules))))))
+      (finally
+        (fs/delete-tree tmp-dir)))))
+
 (deftest merge-components-test
   (testing "merges multiple plugin components"
     (let [c1 {:config-fragment {:mcpServers {:server-a {:url "http://a"}}

test/eca/interpolation_test.clj

@@ -1,17 +1,37 @@
 (ns eca.interpolation-test
   (:require
+   [babashka.fs :as fs]
    [clojure.test :refer [deftest is testing use-fixtures]]
    [eca.interpolation :as interpolation]
    [eca.logger :as logger]))
 
-;; Reset the shell-PATH cache before every test so cache state never leaks
-;; between tests. Tests that exercise the shell query path mock run-process!
-;; (which short-circuits the query to nil via missing-delimiter parse failure)
-;; or stub user-shell-path / query-user-shell-path directly.
+;; Reset process-wide interpolation caches before every test so state never
+;; leaks between tests. Tests that exercise the shell query path mock
+;; run-process! (which short-circuits the query to nil via missing-delimiter
+;; parse failure) or stub user-shell-path / query-user-shell-path directly.
 (use-fixtures :each
   (fn [t]
     (interpolation/reset-shell-path-cache!)
-    (t)))
+    (interpolation/reset-plugin-dirs!)
+    (try
+      (t)
+      (finally
+        (interpolation/reset-plugin-dirs!)))))
+
+(deftest plugin-root-interpolation-test
+  (let [tmp-dir (fs/create-temp-dir)
+        plugin-dir (fs/file tmp-dir "plugin")
+        nested-dir (fs/file plugin-dir "commands")]
+    (try
+      (fs/create-dirs nested-dir)
+      (let [plugin-root (str (fs/canonicalize plugin-dir))]
+        (interpolation/register-plugin-dir! (str plugin-dir))
+        (is (= (str "root=" plugin-root)
+               (interpolation/replace-dynamic-strings "root=${plugin:root}" plugin-dir nil)))
+        (is (= (str "root=" plugin-root)
+               (interpolation/replace-dynamic-strings "root=${plugin:root}" nested-dir nil))))
+      (finally
+        (fs/delete-tree tmp-dir)))))
 
 (deftest augment-path-test
   (testing "non-mac OS: existing PATH returned unchanged"