Add dry_run parameter to file_write tool

src/clojure_mcp/tools/file_write/core.clj

@@ -2,33 +2,34 @@
   "Core implementation for the file-write tool.
    This namespace contains the pure functionality without any MCP-specific code."
   (:require
-    [clojure.java.io :as io]
-    [clojure-mcp.tools.form-edit.pipeline :as pipeline]
-    [clojure-mcp.utils.diff :as diff-utils]
-    [clojure-mcp.linting :as linting]
-    [clojure-mcp.utils.valid-paths :as valid-paths]
-    [rewrite-clj.zip :as z]))
+   [clojure.java.io :as io]
+   [clojure-mcp.tools.form-edit.pipeline :as pipeline]
+   [clojure-mcp.utils.diff :as diff-utils]
+   [clojure-mcp.linting :as linting]
+   [clojure-mcp.utils.valid-paths :as valid-paths]
+   [rewrite-clj.zip :as z]))
 
-  (defn is-clojure-file?
-    "Check if a file is a Clojure-related file based on its extension or Babashka shebang.
+(defn is-clojure-file?
+  "Check if a file is a Clojure-related file based on its extension or Babashka shebang.
 
      Parameters:
      - file-path: Path to the file to check
 
      Returns true for Clojure extensions (.clj, .cljs, .cljc, .edn, .bb) or files with a `bb` shebang."
-    [file-path]
-    (boolean (valid-paths/clojure-file? file-path)))
+  [file-path]
+  (boolean (valid-paths/clojure-file? file-path)))
 
 (defn write-clojure-file
   "Write content to a Clojure file, with linting, formatting, and diffing.
 
    Parameters:
    - file-path: Validated path to the file to write
    - content: Content to write to the file
+   - dry_run: Optional preview mode ('diff' or 'new-source')
 
    Returns:
    - A map with :error, :type, :file-path, and :diff keys"
-  [nrepl-client-atom file-path content]
+  [nrepl-client-atom file-path content dry_run]
   (let [file (io/file file-path)
         file-exists? (.exists file)
         old-content (if file-exists? (slurp file) "")
@@ -50,27 +51,47 @@
                 pipeline/format-source ;; Format the content
                 pipeline/generate-diff ;; Generate diff between old and new content
                 pipeline/determine-file-type ;; Determine if creating or updating
-                pipeline/save-file)] ;; Save the file and get offsets
+                ;; Conditionally skip file save if dry_run is set
+                (fn [ctx]
+                  (if dry_run
+                    ctx
+                    (pipeline/save-file ctx))))]
 
     ;; Format the result for tool consumption
     (if (::pipeline/error result)
       {:error true
        :message (::pipeline/message result)}
-      {:error false
-       :type (::pipeline/type result)
-       :file-path (::pipeline/file-path result)
-       :diff (::pipeline/diff result)})))
+      (cond
+        ;; Return new-source for dry_run="new-source"
+        (= dry_run "new-source")
+        {:error false
+         :dry_run "new-source"
+         :new-source (::pipeline/output-source result)}
+
+        ;; Return just diff for dry_run="diff"
+        (= dry_run "diff")
+        {:error false
+         :dry_run "diff"
+         :diff (::pipeline/diff result)}
+
+        ;; Return full result for normal operation
+        :else
+        {:error false
+         :type (::pipeline/type result)
+         :file-path (::pipeline/file-path result)
+         :diff (::pipeline/diff result)}))))
 
 (defn write-text-file
   "Write content to a non-Clojure text file, with diffing but no linting or formatting.
 
    Parameters:
    - file-path: Validated path to the file to write
    - content: Content to write to the file
+   - dry_run: Optional preview mode ('diff' or 'new-source')
 
    Returns:
    - A map with :error, :type, :file-path, and :diff keys"
-  [file-path content]
+  [file-path content dry_run]
   (try
     (let [file (io/file file-path)
           file-exists? (.exists file)
@@ -82,13 +103,27 @@
                    (diff-utils/generate-unified-diff old-content content))
                  "")]
 
-      ;; Write the content directly
-      (spit file content)
+      (cond
+        ;; Return new-source if dry_run="new-source"
+        (= dry_run "new-source")
+        {:error false
+         :dry_run "new-source"
+         :new-source content}
+
+        ;; Return just diff for dry_run="diff"
+        (= dry_run "diff")
+        {:error false
+         :dry_run "diff"
+         :diff diff}
 
-      {:error false
-       :type (if file-exists? "update" "create")
-       :file-path file-path
-       :diff diff})
+        ;; Normal operation - write and return full result
+        :else
+        (do
+          (spit file content)
+          {:error false
+           :type (if file-exists? "update" "create")
+           :file-path file-path
+           :diff diff})))
     (catch Exception e
       {:error true
        :message (str "Error writing file: " (.getMessage e))})))
@@ -101,10 +136,11 @@
    Parameters:
    - file-path: Validated path to the file to write
    - content: Content to write to the file
+   - dry_run: Optional preview mode ('diff' or 'new-source')
 
    Returns:
    - A map with :error, :type, :file-path, and :diff keys"
-  [nrepl-client-atom file-path content]
+  [nrepl-client-atom file-path content dry_run]
   (if (is-clojure-file? file-path)
-    (write-clojure-file nrepl-client-atom file-path content)
-    (write-text-file file-path content)))
+    (write-clojure-file nrepl-client-atom file-path content dry_run)
+    (write-text-file file-path content dry_run)))

src/clojure_mcp/tools/file_write/tool.clj

@@ -63,7 +63,7 @@ Before using this tool:
    :required [:file_path :content]})
 
 (defmethod tool-system/validate-inputs :file-write [{:keys [nrepl-client-atom]} inputs]
-  (let [{:keys [file_path content]} inputs
+  (let [{:keys [file_path content dry_run]} inputs
         nrepl-client (and nrepl-client-atom @nrepl-client-atom)]
     (when-not file_path
       (throw (ex-info "Missing required parameter: file_path" {:inputs inputs})))
@@ -88,10 +88,11 @@ Before using this tool:
 
       ;; Return validated inputs with normalized path
       {:file-path validated-path
-       :content content})))
+       :content content
+       :dry_run dry_run})))
 
 (defmethod tool-system/execute-tool :file-write [{:keys [nrepl-client-atom]} inputs]
-  (let [{:keys [file-path content]} inputs
+  (let [{:keys [file-path content dry_run]} inputs
         ;; Capture original content - empty string for new files
         _ (when nrepl-client-atom
             (let [file (io/file file-path)]
@@ -105,18 +106,31 @@ Before using this tool:
                  nrepl-client-atom
                  file-path
                  ""))))
-        result (core/write-file nrepl-client-atom file-path content)]
+        result (core/write-file nrepl-client-atom file-path content dry_run)]
     ;; Update the timestamp if write was successful and we have a client atom
-    (when (and nrepl-client-atom (not (:error result)))
+    (when (and nrepl-client-atom (not (:error result)) (not dry_run))
       (file-timestamps/update-file-timestamp-to-current-mtime! nrepl-client-atom file-path))
     result))
 
 (defmethod tool-system/format-results :file-write [_ result]
-  (if (:error result)
+  (cond
     ;; If there's an error, return the error message
+    (:error result)
     {:result [(:message result)]
      :error true}
-    ;; Otherwise, format a successful result
+
+    ;; Check if this is a dry_run with new-source
+    (:new-source result)
+    {:result [(:new-source result)]
+     :error false}
+
+    ;; Check if this is a dry_run with diff only (no file-path)
+    (and (:diff result) (not (:file-path result)))
+    {:result [(:diff result)]
+     :error false}
+
+    ;; Otherwise, format a successful result with preamble
+    :else
     (let [file-type (if (core/is-clojure-file? (:file-path result)) "Clojure" "Text")
           response (str file-type " file " (:type result) "d: " (:file-path result))]
       (if (seq (:diff result))

test/clojure_mcp/tools/file_write/core_test.clj

@@ -66,7 +66,7 @@
   (testing "Creating a new text file"
     (let [new-file (io/file *test-dir* "new-text-file.txt")
           content "This is a brand new file."
-          result (file-write-core/write-text-file (.getPath new-file) content)]
+          result (file-write-core/write-text-file (.getPath new-file) content nil)]
       (is (not (:error result)))
       (is (= "create" (:type result)))
       (is (= (.getPath new-file) (:file-path result)))
@@ -79,7 +79,7 @@
     (let [path (.getPath *test-txt-file*)
           original-content (slurp *test-txt-file*)
           new-content "This is updated content.\nWith new lines."
-          result (file-write-core/write-text-file path new-content)]
+          result (file-write-core/write-text-file path new-content nil)]
       (is (not (:error result)))
       (is (= "update" (:type result)))
       (is (= path (:file-path result)))
@@ -93,7 +93,8 @@
           result (file-write-core/write-clojure-file
                   test-utils/*nrepl-client-atom*
                   (.getPath new-file)
-                  content)]
+                  content
+                  nil)]
       (is (not (:error result)))
       (is (= "create" (:type result)))
       (is (= (.getPath new-file) (:file-path result)))
@@ -107,7 +108,8 @@
           result (file-write-core/write-clojure-file
                   test-utils/*nrepl-client-atom*
                   path
-                  new-content)]
+                  new-content
+                  nil)]
       (is (not (:error result)))
       (is (= "update" (:type result)))
       (is (= path (:file-path result)))
@@ -120,7 +122,8 @@
           result (file-write-core/write-clojure-file
                   test-utils/*nrepl-client-atom*
                   path
-                  unformatted-content)]
+                  unformatted-content
+                  nil)]
       (is (not (:error result)))
       (is (= "update" (:type result)))
       (is (not (str/includes? (slurp *test-clj-file*) "poorly-formatted-fn[x]")))
@@ -132,7 +135,8 @@
           result (file-write-core/write-clojure-file
                   test-utils/*nrepl-client-atom*
                   path
-                  content-with-missing-paren)]
+                  content-with-missing-paren
+                  nil)]
       (is (not (:error result)))
       (is (= "update" (:type result)))
       (let [saved-content (slurp *test-clj-file*)]
@@ -146,7 +150,8 @@
           result (file-write-core/write-clojure-file
                   test-utils/*nrepl-client-atom*
                   path
-                  content-with-mismatched-brackets)]
+                  content-with-mismatched-brackets
+                  nil)]
       (is (not (:error result)))
       (is (= "update" (:type result)))
       (let [saved-content (slurp *test-clj-file*)]
@@ -161,7 +166,8 @@
           result (file-write-core/write-clojure-file
                   test-utils/*nrepl-client-atom*
                   path
-                  content-with-syntax-error)]
+                  content-with-syntax-error
+                  nil)]
       ;; The test should fail with a specific error
       (is (:error result) "Should have error for non-repairable syntax error")
       (when (:message result)
@@ -176,7 +182,8 @@
           content "(ns dispatch.test)"
           result (file-write-core/write-file test-utils/*nrepl-client-atom*
                                              (.getPath clj-file)
-                                             content)]
+                                             content
+                                             nil)]
       (is (not (:error result)))
       (is (= "create" (:type result)))
       (is (.exists clj-file))
@@ -187,7 +194,8 @@
           content "Plain text content"
           result (file-write-core/write-file test-utils/*nrepl-client-atom*
                                              (.getPath txt-file)
-                                             content)]
+                                             content
+                                             nil)]
       (is (not (:error result)))
       (is (= "create" (:type result)))
       (is (.exists txt-file))