Add support for .geminiignore file (#757)

packages/core/src/tools/read-file.ts

@@ -5,10 +5,12 @@
  */
 
 import path from 'path';
+import micromatch from 'micromatch';
 import { SchemaValidator } from '../utils/schemaValidator.js';
 import { makeRelative, shortenPath } from '../utils/paths.js';
 import { BaseTool, ToolResult } from './tools.js';
 import { isWithinRoot, processSingleFileContent } from '../utils/fileUtils.js';
+import { Config } from '../config/config.js';
 
 /**
  * Parameters for the ReadFile tool
@@ -35,8 +37,12 @@ export interface ReadFileToolParams {
  */
 export class ReadFileTool extends BaseTool<ReadFileToolParams, ToolResult> {
   static readonly Name: string = 'read_file';
+  private readonly geminiIgnorePatterns: string[];
 
-  constructor(private rootDirectory: string) {
+  constructor(
+    private rootDirectory: string,
+    config: Config,
+  ) {
     super(
       ReadFileTool.Name,
       'ReadFile',
@@ -64,6 +70,7 @@ export class ReadFileTool extends BaseTool<ReadFileToolParams, ToolResult> {
       },
     );
     this.rootDirectory = path.resolve(rootDirectory);
+    this.geminiIgnorePatterns = config.getGeminiIgnorePatterns() || [];
   }
 
   validateToolParams(params: ReadFileToolParams): string | null {
@@ -89,6 +96,19 @@ export class ReadFileTool extends BaseTool<ReadFileToolParams, ToolResult> {
     if (params.limit !== undefined && params.limit <= 0) {
       return 'Limit must be a positive number';
     }
+
+    // Check against .geminiignore patterns
+    if (this.geminiIgnorePatterns.length > 0) {
+      const relativePath = makeRelative(params.path, this.rootDirectory);
+      if (micromatch.isMatch(relativePath, this.geminiIgnorePatterns)) {
+        // Get patterns that matched to show in the error message
+        const matchingPatterns = this.geminiIgnorePatterns.filter((p) =>
+          micromatch.isMatch(relativePath, p),
+        );
+        return `File path '${shortenPath(relativePath)}' is ignored by the following .geminiignore pattern(s):\n\n${matchingPatterns.join('\n')}`;
+      }
+    }
+
     return null;
   }