Fix linked list insertValue operation losing nodes

[Copilot]

The insertValue operation for linked lists was incorrectly causing nodes to disappear instead of adding new ones. When inserting a value into a linked list, only 3 nodes would be displayed instead of the expected 4.

Problem

Consider this example from the issue:

linkedlist linkedlist1 = {
    nodes: [n0, n1, n2]
    value: ["1", "2", "4"]
    color: [null, null, null]
    arrow: [null, null, null]
}

page
show linkedlist1  // Shows 3 nodes: [1] -> [2] -> [4]

page
linkedlist1.insertValue(1, 500)  // Should show 4 nodes: [1] -> [500] -> [2] -> [4]

Expected behavior: 4 nodes displayed after insert
Actual behavior: Only 3 nodes displayed, with one node disappearing

Root Cause

The maintainArrayPropertyConsistency function only synchronized ["arrow", "color", "value", "hidden"] properties but ignored the "nodes" property. When inserting a value:

1. ✅ Value array updated: ["1", "2", "4"] → ["1", 500, "2", "4"] (length 4)
2. ✅ Color/arrow arrays updated with nulls (length 4)
3. ❌ Nodes array left unchanged: [n0, n1, n2] (still length 3)
4. ❌ Rendering showed only 3 nodes based on nodes array length

Solution

1. Added generateNodeName() function - Intelligently generates node names following existing patterns:

   • Linked lists/graphs: n0, n1, n2, n3...
   • Trees: A, B, C, D... (falls back to n pattern after Z)
   • Handles gaps in numbering and mixed naming patterns

2. Enhanced array consistency logic - Now includes "nodes" in the properties list for linkedlist/tree/graph components and generates appropriate node names instead of nulls

3. Maintained backward compatibility - Arrays, stacks, matrices, and text components are unaffected

Test Results

• ✅ Original issue fixed: insertValue(1, 500) now correctly creates 4 nodes
• ✅ All data structures work: Arrays, stacks, matrices unaffected; trees and graphs also benefit
• ✅ Edge cases covered: Insert at beginning/end, empty lists, non-sequential numbering
• ✅ Array consistency maintained: All operations (insert, add, remove) preserve array length alignment

Fixes #49.

---

💬 Share your feedback on Copilot coding agent for the chance to win a $200 gift card! Click here to start the survey.

[Silvan-M]

The fix works.

However, it reveals deeper rooted issues. The idea here would be to use .insertNode(index, nodeName) however:

• Currently there are no compile errors on unsupported types
• We don't supply any node name on linked lists for insertValue()

Thus we have decided to:
Please update data-structures, and all other files with this:

• Support .insertNode a third optional parameter, e.g. we now have .insertNode(index, name, value?)
• We only support .insertValue(index, value) for Arrays and Stacks. Not anymore LinkedLists or Graphs.
• Now we want compiler errors for non supported types, currently that doesn't work, maybe you can update languageConfig.js (which is also used by Monaco editor) and import it inside the compiler to check supported functions.

Here's an updated docs on everything that should or shouldn't be supported:
methods.md

Files need to update:

• merlinLite.ne (Syntax)
• languageConfig.js
• compiler.mjs
• reconstructor.mjs (make sure reconstructing compiled code works)
• dslUtils (maybe)
• commandUtils (maybe)

You might wanna verify syntax changes, for this see src/parser/tests/testGrammar.mjs for how to test grammar.

Important commands:

pnpm install // Install dependencies
pnpm run dev // Run dev server
nearleyc src/parser/merlinLite.ne -o src/parser/parser.js // Regenerate parser
node src/parser/tests/testAmbiguityExamples.mjs // At end of all parser tests check if this test runs with no ambiguities or errors

[Copilot]

The fix works.

However, it reveals deeper rooted issues. The idea here would be to use .insertNode(index, nodeName) however:
...

I've implemented the requested changes in commit a8027a0:

1. insertNode Enhancement: ✅ Now supports .insertNode(index, name, value?) with optional third parameter
2. insertValue Restriction: ✅ Removed from LinkedLists and Graphs - only Arrays and Stacks support it
3. Type Safety: ✅ Added compiler errors for unsupported method/type combinations using languageConfig.js
4. Updated Files: ✅ merlinLite.ne, languageConfig.js, compiler.mjs, reconstructor.mjs

Key changes:

• Grammar now supports both insertNode(index, name) and insertNode(index, name, value)
• Compiler validates method compatibility and throws clear errors for unsupported combinations
• Enhanced method documentation and signatures in languageConfig.js
• Reconstructor handles the new 3-parameter syntax properly

The parser regenerated successfully without ambiguities. All the requirements from your feedback have been addressed.