Better multi-line search/replace matching

Author: mrubens

src/core/diff/strategies/__tests__/search-replace.test.ts

@@ -106,6 +106,81 @@ function test() {
 `)
         })
 
+        it('should handle tab-based indentation', () => {
+            const originalContent = "function test() {\n\treturn true;\n}\n"
+            const diffContent = `test.ts
+<<<<<<< SEARCH
+function test() {
+\treturn true;
+}
+=======
+function test() {
+\treturn false;
+}
+>>>>>>> REPLACE`
+
+            const result = strategy.applyDiff(originalContent, diffContent)
+            expect(result).toBe("function test() {\n\treturn false;\n}\n")
+        })
+
+        it('should preserve mixed tabs and spaces', () => {
+            const originalContent = "\tclass Example {\n\t    constructor() {\n\t\tthis.value = 0;\n\t    }\n\t}"
+            const diffContent = `test.ts
+<<<<<<< SEARCH
+\tclass Example {
+\t    constructor() {
+\t\tthis.value = 0;
+\t    }
+\t}
+=======
+\tclass Example {
+\t    constructor() {
+\t\tthis.value = 1;
+\t    }
+\t}
+>>>>>>> REPLACE`
+
+            const result = strategy.applyDiff(originalContent, diffContent)
+            expect(result).toBe("\tclass Example {\n\t    constructor() {\n\t\tthis.value = 1;\n\t    }\n\t}")
+        })
+
+        it('should handle additional indentation with tabs', () => {
+            const originalContent = "\tfunction test() {\n\t\treturn true;\n\t}"
+            const diffContent = `test.ts
+<<<<<<< SEARCH
+function test() {
+\treturn true;
+}
+=======
+function test() {
+\t// Add comment
+\treturn false;
+}
+>>>>>>> REPLACE`
+
+            const result = strategy.applyDiff(originalContent, diffContent)
+            expect(result).toBe("\tfunction test() {\n\t\t// Add comment\n\t\treturn false;\n\t}")
+        })
+
+        it('should preserve exact indentation characters when adding lines', () => {
+            const originalContent = "\tfunction test() {\n\t\treturn true;\n\t}"
+            const diffContent = `test.ts
+<<<<<<< SEARCH
+\tfunction test() {
+\t\treturn true;
+\t}
+=======
+\tfunction test() {
+\t\t// First comment
+\t\t// Second comment
+\t\treturn true;
+\t}
+>>>>>>> REPLACE`
+
+            const result = strategy.applyDiff(originalContent, diffContent)
+            expect(result).toBe("\tfunction test() {\n\t\t// First comment\n\t\t// Second comment\n\t\treturn true;\n\t}")
+        })
+
         it('should return false if search content does not match', () => {
             const originalContent = `function hello() {
     console.log("hello")

src/core/diff/strategies/search-replace.ts

@@ -17,13 +17,13 @@ Parameters:
 Format:
 1. First line must be the file path
 2. Followed by search/replace blocks:
-   \`\`\`
-   <<<<<<< SEARCH
-   [exact content to find including whitespace]
-   =======
-   [new content to replace with]
-   >>>>>>> REPLACE
-   \`\`\`
+    \`\`\`
+    <<<<<<< SEARCH
+    [exact content to find including whitespace]
+    =======
+    [new content to replace with]
+    >>>>>>> REPLACE
+    \`\`\`
 
 Example:
 
@@ -105,18 +105,38 @@ Your search/replace content here
         // Get the matched lines from the original content
         const matchedLines = originalLines.slice(matchIndex, matchIndex + searchLines.length);
 
-        // For each line in the match, get its indentation
-        const indentations = matchedLines.map(line => {
-            const match = line.match(/^(\s*)/);
-            return match ? match[1] : '';
+        // Get the exact indentation (preserving tabs/spaces) of each line
+        const originalIndents = matchedLines.map(line => {
+            const match = line.match(/^[\t ]*/);
+            return match ? match[0] : '';
         });
 
-        // Apply the replacement while preserving indentation
+        // Get the exact indentation of each line in the search block
+        const searchIndents = searchLines.map(line => {
+            const match = line.match(/^[\t ]*/);
+            return match ? match[0] : '';
+        });
+        
+        // Apply the replacement while preserving exact indentation
         const indentedReplace = replaceLines.map((line, i) => {
-            // Use the indentation from the corresponding line in the matched block
-            // If we have more lines than the original, use the last indentation
-            const indent = indentations[Math.min(i, indentations.length - 1)];
-            return indent + line.trim();
+            // Get the corresponding original and search indentations
+            const originalIndent = originalIndents[Math.min(i, originalIndents.length - 1)];
+            const searchIndent = searchIndents[Math.min(i, searchIndents.length - 1)];
+            
+            // Get the current line's indentation
+            const currentIndentMatch = line.match(/^[\t ]*/);
+            const currentIndent = currentIndentMatch ? currentIndentMatch[0] : '';
+            
+            // If this line has the same indentation level as the search block,
+            // use the original indentation. Otherwise, calculate the difference
+            // and preserve the exact type of whitespace characters
+            if (currentIndent.length === searchIndent.length) {
+                return originalIndent + line.trim();
+            } else {
+                // Calculate additional indentation needed
+                const additionalIndent = currentIndent.slice(searchIndent.length);
+                return originalIndent + additionalIndent + line.trim();
+            }
         });
 
         // Construct the final content
@@ -125,4 +145,4 @@ Your search/replace content here
 
         return [...beforeMatch, ...indentedReplace, ...afterMatch].join('\n');
     }
-}
+}