feat(commands): Enable @file processing in TOML commands (#6716)

packages/cli/src/services/prompt-processors/injectionParser.ts

@@ -0,0 +1,89 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/**
+ * Represents a single detected injection site in a prompt string.
+ */
+export interface Injection {
+  /** The content extracted from within the braces (e.g., the command or path), trimmed. */
+  content: string;
+  /** The starting index of the injection (inclusive, points to the start of the trigger). */
+  startIndex: number;
+  /** The ending index of the injection (exclusive, points after the closing '}'). */
+  endIndex: number;
+}
+
+/**
+ * Iteratively parses a prompt string to extract injections (e.g., !{...} or @{...}),
+ * correctly handling nested braces within the content.
+ *
+ * This parser relies on simple brace counting and does not support escaping.
+ *
+ * @param prompt The prompt string to parse.
+ * @param trigger The opening trigger sequence (e.g., '!{', '@{').
+ * @param contextName Optional context name (e.g., command name) for error messages.
+ * @returns An array of extracted Injection objects.
+ * @throws Error if an unclosed injection is found.
+ */
+export function extractInjections(
+  prompt: string,
+  trigger: string,
+  contextName?: string,
+): Injection[] {
+  const injections: Injection[] = [];
+  let index = 0;
+
+  while (index < prompt.length) {
+    const startIndex = prompt.indexOf(trigger, index);
+
+    if (startIndex === -1) {
+      break;
+    }
+
+    let currentIndex = startIndex + trigger.length;
+    let braceCount = 1;
+    let foundEnd = false;
+
+    while (currentIndex < prompt.length) {
+      const char = prompt[currentIndex];
+
+      if (char === '{') {
+        braceCount++;
+      } else if (char === '}') {
+        braceCount--;
+        if (braceCount === 0) {
+          const injectionContent = prompt.substring(
+            startIndex + trigger.length,
+            currentIndex,
+          );
+          const endIndex = currentIndex + 1;
+
+          injections.push({
+            content: injectionContent.trim(),
+            startIndex,
+            endIndex,
+          });
+
+          index = endIndex;
+          foundEnd = true;
+          break;
+        }
+      }
+      currentIndex++;
+    }
+
+    // Check if the inner loop finished without finding the closing brace.
+    if (!foundEnd) {
+      const contextInfo = contextName ? ` in command '${contextName}'` : '';
+      // Enforce strict parsing (Comment 1) and clarify limitations (Comment 2).
+      throw new Error(
+        `Invalid syntax${contextInfo}: Unclosed injection starting at index ${startIndex} ('${trigger}'). Ensure braces are balanced. Paths or commands with unbalanced braces are not supported directly.`,
+      );
+    }
+  }
+
+  return injections;
+}