refactor: extract shared platform-default-path helper in config.ts

[carlos-alm]

Summary

• getDefaultUserConfigPath() and resolveUserConfigPath() duplicated the same XDG_CONFIG_HOME / Windows %APPDATA% / ~/.config three-way branch.
• Extracted into a shared private helper computePlatformDefaultConfigPath(home); both functions now call it. resolveUserConfigPath() still layers its own existsSync checks on top, unchanged. Pure dedup — priority order and path shapes preserved exactly.

Closes #1746

Test plan

• npm test — full suite green (3490 passed, 0 failed)
• npm run lint — clean
• tests/unit/config-user.test.ts (27 tests covering resolveUserConfigPath) unaffected

Stacked on #1854 (base branch fix/issue-1745-remote-embed-json-error) — only the config.ts diff is this issue's change.

[greptile-apps]

Greptile Summary

This PR extracts the XDG / Windows / fallback three-way branch that was duplicated verbatim between getDefaultUserConfigPath() and resolveUserConfigPath() into a single private helper computePlatformDefaultConfigPath(home). Both callers now delegate the path-computation to the helper while preserving their own responsibility: the getDefault function still handles the CODEGRAPH_USER_CONFIG env var early-return, and resolveUserConfigPath still layers existsSync checks on top.

• Extracted computePlatformDefaultConfigPath(home?) helper from src/infrastructure/config.ts — pure dedup of ~12 lines shared by two functions, with priority order (XDG → APPDATA → ~/.config) unchanged.
• resolveUserConfigPath passes its already-computed home to the helper, avoiding a redundant os.homedir() call; getDefaultUserConfigPath uses the default parameter so the call site stays clean.

Confidence Score: 5/5

Safe to merge — pure deduplication with no logic changes.

The only changed file consolidates identical code into a shared helper. The priority order (XDG → APPDATA → ~/.config), the env-var early-returns, and the existsSync layering in resolveUserConfigPath are all preserved exactly. resolveUserConfigPath still passes its already-computed home to the helper, avoiding a redundant os.homedir() call, which is a minor improvement. There are no new code paths, no changed conditions, and no altered return values.

No files require special attention.

Important Files Changed

Filename	Overview
src/infrastructure/config.ts	Extracted shared helper computePlatformDefaultConfigPath; logic and priority order are preserved exactly; no behavioural changes.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A1["getDefaultUserConfigPath()"] -->|"CODEGRAPH_USER_CONFIG set"| R1["return envPath"]
    A1 -->|"env var absent"| H["computePlatformDefaultConfigPath(home?)"]

    A2["resolveUserConfigPath()"] -->|"CODEGRAPH_USER_CONFIG set"| E2{"existsSync(envPath)"}
    E2 -->|"yes"| R2["return envPath"]
    E2 -->|"no"| R3["return null"]
    A2 -->|"env var absent"| HH["computePlatformDefaultConfigPath(home)"]

    H --> X{"XDG_CONFIG_HOME set?"}
    HH --> X
    X -->|"yes"| P1["$XDG_CONFIG_HOME/codegraph/config.json"]
    X -->|"no"| W{"win32?"}
    W -->|"yes + APPDATA set"| P2["%APPDATA%/codegraph/config.json"]
    W -->|"yes + APPDATA unset"| P3["~/.config/codegraph/config.json"]
    W -->|"no"| P3

    HH --> E3{"existsSync(platformDefault)"}
    E3 -->|"yes"| R4["return platformDefault"]
    E3 -->|"no"| L{"existsSync(legacyPath)"}
    L -->|"yes"| R5["return ~/.codegraph/config.json"]
    L -->|"no"| R6["return null"]

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flowchart TD
    A1["getDefaultUserConfigPath()"] -->|"CODEGRAPH_USER_CONFIG set"| R1["return envPath"]
    A1 -->|"env var absent"| H["computePlatformDefaultConfigPath(home?)"]

    A2["resolveUserConfigPath()"] -->|"CODEGRAPH_USER_CONFIG set"| E2{"existsSync(envPath)"}
    E2 -->|"yes"| R2["return envPath"]
    E2 -->|"no"| R3["return null"]
    A2 -->|"env var absent"| HH["computePlatformDefaultConfigPath(home)"]

    H --> X{"XDG_CONFIG_HOME set?"}
    HH --> X
    X -->|"yes"| P1["$XDG_CONFIG_HOME/codegraph/config.json"]
    X -->|"no"| W{"win32?"}
    W -->|"yes + APPDATA set"| P2["%APPDATA%/codegraph/config.json"]
    W -->|"yes + APPDATA unset"| P3["~/.config/codegraph/config.json"]
    W -->|"no"| P3

    HH --> E3{"existsSync(platformDefault)"}
    E3 -->|"yes"| R4["return platformDefault"]
    E3 -->|"no"| L{"existsSync(legacyPath)"}
    L -->|"yes"| R5["return ~/.codegraph/config.json"]
    L -->|"no"| R6["return null"]

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_{Reviews (2): Last reviewed commit: "fix: resolve merge conflicts with main (..." | Re-trigger Greptile}

[github-actions]

Codegraph Impact Analysis

3 functions changed → 38 callers affected across 24 files

• computePlatformDefaultConfigPath in src/infrastructure/config.ts:297 (13 transitive callers)
• getDefaultUserConfigPath in src/infrastructure/config.ts:322 (3 transitive callers)
• resolveUserConfigPath in src/infrastructure/config.ts:340 (35 transitive callers)