fix: global struct variable debugger shows no values

[thiagoralves]

Summary

• Fixes the debug path prefix used when resolving indices for members of global (external) struct/FB variables
• Global variables use CONFIG0__ prefix in debug.c, but the variableInfoMap building code always constructed local RES0__INSTANCE paths, causing all index lookups for global struct members to fail silently
• Checks variable.class === 'external' in three code paths that process nested FB/struct members and switches to buildGlobalDebugPath accordingly

Fixes #638

Test plan

• Create a project with a struct type (e.g., MY_STRUCT with FIELD1: INT, FIELD2: BOOL)
• Declare a global variable of that struct type (VAR_GLOBAL)
• Reference it in a program via VAR_EXTERNAL
• Start the debugger and verify struct member values are displayed for the global variable
• Verify local struct variables still work correctly (no regression)
• Verify local FB instances still debug correctly (no regression)

🤖 Generated with Claude Code

Summary by CodeRabbit

Release Notes

• Bug Fixes

  • Improved handling of external and global variables during debugging sessions. Variables defined outside the current scope are now properly resolved and indexed, ensuring accurate real-time monitoring and inspection.

• Refactor

  • Optimized internal path resolution logic for external variable references to enhance performance and consistency across nested variable processing.

[coderabbitai]

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ℹ️ Recent review info

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📥 Commits

Reviewing files that changed from the base of the PR and between e414315 and 2a60357.

📒 Files selected for processing (1)

• src/renderer/screens/workspace-screen.tsx

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Walkthrough

The PR adds support for debugging global (external) function block variables by introducing a buildGlobalDebugPath utility function and modifying the workspace screen's variable resolution logic to use global path prefixes instead of instance-based paths when processing external FB/UDT members and updating index mappings.

Changes

Cohort / File(s)	Summary
Debugger Path Resolution Enhancement src/renderer/screens/workspace-screen.tsx	Modified variable indexing and polling logic to detect external FB instances and resolve their debug paths using buildGlobalDebugPath instead of instance-based paths. Updated nested variable processing, top-level FB visitation, and composite-key index mapping to consistently apply global path resolution for external entities.
Global Path Builder Utility @root/utils/debug-variable-finder	Added new buildGlobalDebugPath(name: string): string function to generate global-prefixed debug paths for external FB/UDT variables.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Possibly related PRs

• fix: Global variables support - types and debugger mapping #520: Modifies debugger indexing logic for external/global variables by adding helpers and switching path resolution to use global prefixes for correctly mapping external FB/UDT members.
• fix: display global variable values consistently across all programs #597: Changes how global/external variables are resolved and polled in the workspace, updating index-to-VariableInfo mappings alongside this PR's global debug path handling.
• fix: show online debug values for structured data types and FB instances #614: Modifies debug-variable path resolution and FB/UDT variable traversal, including how debug indexes and paths are constructed and looked up.

Poem

🐰 Global structs hop through the debugger now,
No longer lost in darkness, taking a bow!
Paths shine bright with global prefixes aglow,
External FBs dance—their values steal the show! ✨

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title 'fix: global struct variable debugger shows no values' directly and concisely describes the main change—fixing debug visibility for global struct variables.
Description check	✅ Passed	The PR description includes a clear summary, test plan, and reference to the linked issue; however, the DOD checklist template sections are missing.
Linked Issues check	✅ Passed	The PR successfully addresses issue #638 by fixing the debug path prefix mismatch (CONFIG0__ vs RES0__INSTANCE) for global struct variables through detection and proper handling of external variables.
Out of Scope Changes check	✅ Passed	All changes are focused on fixing the global struct variable debugger issue (#638); the addition of buildGlobalDebugPath and its usage in three code paths are directly related to this objective.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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✨ Finishing Touches

• 📝 Generate docstrings (stacked PR)
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• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch fix/global-struct-debugger-index

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