fix(Microsoft Outlook Trigger Node): Show nested subfolders in folder dropdowns

[BerniWittmann]

Summary

The Microsoft Outlook Trigger's "Folders to Include" / "Folders to Exclude" dropdowns only surfaced top-level mail folders, so users couldn't target Inbox subfolders. Two bugs combined: getSubfolders used a non-paginated request (dropping children past the first page), and getFolders called it without the addPathToDisplayName flag, so subfolders rendered as bare names and looked indistinguishable from top-level folders.

This change switches child folder fetches to microsoftApiRequestAllItems for full pagination and enables the path prefix in both getFolders (loadOptions) and searchFolders (resource locator), so picker entries now render as Inbox/Work/Q2. The action node's message-filter dropdown benefits from the same fix.

How to test: Add a Microsoft Outlook Trigger, open Filters → Folders to Include, and confirm nested subfolders appear with full paths. Verify the same on Microsoft Outlook → Message → Get Many → Filters. Unit tests cover pagination via @odata.nextLink, recursive path building, and the childFolderCount === 0 short-circuit.

Related Linear tickets, Github issues, and Community forum posts

https://linear.app/n8n/issue/NODE-4852
Fixes #17078

Review / Merge checklist

• I have seen this code, I have run this code, and I take responsibility for this code.
• PR title and summary are descriptive. (conventions)
• Docs updated or follow-up ticket created.
• Tests included.
• PR Labeled with `Backport to Beta`, `Backport to Stable`, or `Backport to v1` (if the PR is an urgent fix that needs to be backported)

🤖 PR Summary generated by AI

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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[github-actions]

Performance Comparison

Comparing current → latest master → 14-day baseline

docker-stats

Metric	Current	Latest Master	Baseline (avg)	vs Master	vs Baseline	Status
docker-image-size-runners	386.00 MB	386.00 MB	392.50 MB (σ 11.06)	+0.0%	-1.7%	✅
docker-image-size-n8n	1269.76 MB	1269.76 MB	1273.60 MB (σ 10.49)	+0.0%	-0.3%	✅

Memory consumption baseline with starter plan resources

Metric	Current	Latest Master	Baseline (avg)	vs Master	vs Baseline	Status
memory-rss-baseline	222.46 MB	278.98 MB	289.99 MB (σ 41.20)	-20.3%	-23.3%	⚠️
memory-heap-used-baseline	115.36 MB	114.41 MB	114.45 MB (σ 0.27)	+0.8%	+0.8%	🔴

Idle baseline with Instance AI module loaded

Metric	Current	Latest Master	Baseline (avg)	vs Master	vs Baseline	Status
instance-ai-heap-used-baseline	187.19 MB	186.52 MB	186.43 MB (σ 0.26)	+0.4%	+0.4%	🔴
instance-ai-rss-baseline	343.68 MB	389.20 MB	366.52 MB (σ 22.66)	-11.7%	-6.2%	⚠️

How to read this table

• Current: This PR's value (or latest master if PR perf tests haven't run)
• Latest Master: Most recent nightly master measurement
• Baseline: Rolling 14-day average from master
• vs Master: PR impact (current vs latest master)
• vs Baseline: Drift from baseline (current vs rolling avg)
• Status: ✅ within 1σ | ⚠️ 1-2σ | 🔴 >2σ regression

[cubic-dev-ai]

No issues found across 6 files

Architecture diagram

sequenceDiagram
    participant UI as n8n UI (Dropdown/Locator)
    participant Node as Outlook Node (Methods)
    participant Transport as Subfolder Helper (getSubfolders)
    participant Helper as MS API Helper (RequestAllItems)
    participant Graph as Microsoft Graph API
    
    Note over UI,Graph: Folder Retrieval Flow (loadOptions or listSearch)
    
    UI->>Node: Request folders list
    Node->>Helper: GET /mailFolders
    Helper->>Graph: Request top-level folders
    Graph-->>Helper: Return folder list
    Helper-->>Node: Return folder objects
    
    Node->>Transport: CHANGED: getSubfolders(folders, addPath=true)
    
    loop For each folder where childFolderCount > 0
        Transport->>Helper: CHANGED: Fetch ALL children via microsoftApiRequestAllItems
        
        loop Pagination
            Helper->>Graph: GET .../childFolders
            Graph-->>Helper: Return items + @odata.nextLink
        end
        
        Helper-->>Transport: Return flattened list of subfolders
        
        opt NEW: if addPathToDisplayName is true
            Transport->>Transport: Recursively prepend parent path<br/>(e.g., "Inbox/Work/Q2")
        end
    end
    
    Transport-->>Node: Return complete flat list with paths
    Node-->>UI: Return INodePropertyOptions (Display Name + ID)

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[alexander-gekov]

Tested and subfolders appear correctly in the two places mentioned in the description 👍

[n8n-assistant]

Got released with [email protected]