Merge pull request #5 from kettle-rb/fix/infinite-recursion-on-non-mergeable-stmt

Author: pboling

CHANGELOG.md

@@ -20,6 +20,10 @@ Please file a bug if you notice a violation of semantic versioning.
 
 ### Added
 
+- `body_has_mergeable_statements?` private method to check if a block body contains statements that can be signature-matched
+- `mergeable_statement?` private method to determine if a node type can generate signatures for merging
+- `max_recursion_depth` option (defaults to `Float::INFINITY`) as a safety valve for edge cases
+
 ### Changed
 
 ### Deprecated
@@ -28,6 +32,8 @@ Please file a bug if you notice a violation of semantic versioning.
 
 ### Fixed
 
+- **Fixed infinite recursion** when merging `CallNode` blocks (like `git_source`) that have matching signatures but non-mergeable body content (e.g., just string literals). The fix detects when a block body contains only literals/expressions with no signature-matchable statements and treats the node atomically instead of recursing.
+
 ### Security
 
 ## [1.1.1] - 2025-12-04

README.md

@@ -298,6 +298,33 @@ merger = Prism::Merge::SmartMerger.new(
 # Result: Existing configs keep destination values, new configs added from template
 ```
 
+### Recursion Depth Limit
+
+Prism::Merge automatically detects when block bodies contain only literals or simple expressions (no mergeable statements) and treats them atomically. However, as a safety valve for edge cases, you can limit recursion depth:
+
+```ruby
+# Limit recursive merging to 3 levels deep
+merger = Prism::Merge::SmartMerger.new(
+  template,
+  destination,
+  max_recursion_depth: 3,
+)
+
+# Disable recursive merging entirely (treat all nodes atomically)
+merger = Prism::Merge::SmartMerger.new(
+  template,
+  destination,
+  max_recursion_depth: 0,
+)
+```
+
+**When to use:**
+
+- **`Float::INFINITY`** (default) - Normal operation, recursion terminates naturally based on content analysis.
+  - NOTE: If you get `stack level too deep (SystemStackError)`, please file a [bug](https://github.com/kettle-rb/prism-merge/issues)!
+- **Finite value** - Safety valve if you encounter edge cases with unexpected deep recursion
+- **`0`** - Disable recursive merging entirely; all matching nodes are treated atomically
+
 ### Custom Signature Generator
 
 By default, Prism::Merge uses intelligent structural signatures to match nodes. The signature determines how nodes are matched between template and destination files.
@@ -332,7 +359,7 @@ The following node types support **recursive body merging**, where nested conten
 - `ClassNode` - class bodies are recursively merged
 - `ModuleNode` - module bodies are recursively merged
 - `SingletonClassNode` - singleton class bodies are recursively merged
-- `CallNode` with block - block bodies are recursively merged (e.g., `configure do ... end`)
+- `CallNode` with block - block bodies are recursively merged **only when the body contains mergeable statements** (e.g., `describe do ... end` with nested `it` blocks). Blocks containing only literals or simple expressions (like `git_source(:github) { |repo| "https://..." }`) are treated atomically.
 - `BeginNode` - begin/rescue/ensure blocks are recursively merged
 
 #### Custom Signature Generator

docs/Prism.html

@@ -142,7 +142,7 @@ <h5 class="example_title"><div class='inline'><p>With debug information</p>
 </div>
 
       <div id="footer">
-  Generated on Thu Dec  4 15:41:08 2025 by
+  Generated on Thu Dec  4 17:20:40 2025 by
   <a href="https://yardoc.org" title="Yay! A Ruby Documentation Tool" target="_parent">yard</a>
   0.9.37 (ruby-3.4.7).
 </div>

docs/Prism/Merge.html

@@ -158,7 +158,7 @@ <h2>
 </div>
 
       <div id="footer">
-  Generated on Thu Dec  4 15:41:08 2025 by
+  Generated on Thu Dec  4 17:20:40 2025 by
   <a href="https://yardoc.org" title="Yay! A Ruby Documentation Tool" target="_parent">yard</a>
   0.9.37 (ruby-3.4.7).
 </div>

docs/Prism/Merge/ConflictResolver.html

@@ -852,7 +852,7 @@ <h3 class="signature first" id="resolve-instance_method">
 </div>
 
       <div id="footer">
-  Generated on Thu Dec  4 15:41:08 2025 by
+  Generated on Thu Dec  4 17:20:41 2025 by
   <a href="https://yardoc.org" title="Yay! A Ruby Documentation Tool" target="_parent">yard</a>
   0.9.37 (ruby-3.4.7).
 </div>

docs/Prism/Merge/DebugLogger.html

@@ -322,7 +322,7 @@ <h3 class="signature first" id="debug-class_method">
 </div>
 
       <div id="footer">
-  Generated on Thu Dec  4 15:41:08 2025 by
+  Generated on Thu Dec  4 17:20:40 2025 by
   <a href="https://yardoc.org" title="Yay! A Ruby Documentation Tool" target="_parent">yard</a>
   0.9.37 (ruby-3.4.7).
 </div>

docs/Prism/Merge/DestinationParseError.html

@@ -175,7 +175,7 @@ <h2>Constructor Details</h2>
 </div>
 
       <div id="footer">
-  Generated on Thu Dec  4 15:41:08 2025 by
+  Generated on Thu Dec  4 17:20:40 2025 by
   <a href="https://yardoc.org" title="Yay! A Ruby Documentation Tool" target="_parent">yard</a>
   0.9.37 (ruby-3.4.7).
 </div>

docs/Prism/Merge/Error.html

@@ -128,7 +128,7 @@ <h2>Direct Known Subclasses</h2>
 </div>
 
       <div id="footer">
-  Generated on Thu Dec  4 15:41:08 2025 by
+  Generated on Thu Dec  4 17:20:40 2025 by
   <a href="https://yardoc.org" title="Yay! A Ruby Documentation Tool" target="_parent">yard</a>
   0.9.37 (ruby-3.4.7).
 </div>

docs/Prism/Merge/FileAligner.html

@@ -633,7 +633,7 @@ <h3 class="signature first" id="align-instance_method">
 </div>
 
       <div id="footer">
-  Generated on Thu Dec  4 15:41:08 2025 by
+  Generated on Thu Dec  4 17:20:40 2025 by
   <a href="https://yardoc.org" title="Yay! A Ruby Documentation Tool" target="_parent">yard</a>
   0.9.37 (ruby-3.4.7).
 </div>

docs/Prism/Merge/FileAligner/Anchor.html

@@ -901,7 +901,7 @@ <h3 class="signature " id="template_range-instance_method">
 </div>
 
       <div id="footer">
-  Generated on Thu Dec  4 15:41:08 2025 by
+  Generated on Thu Dec  4 17:20:41 2025 by
   <a href="https://yardoc.org" title="Yay! A Ruby Documentation Tool" target="_parent">yard</a>
   0.9.37 (ruby-3.4.7).
 </div>