fix: resolve CI/CD failures in Rust and C# workflows

.github/workflows/csharp.yml

@@ -2,15 +2,15 @@ name: csharp
 
 on:
   push:
-    branches: main 
+    branches: main
     paths:
       - 'csharp/**'
       - '.github/workflows/csharp.yml'
 env:
   NUGETTOKEN: ${{ secrets.NUGET_TOKEN }}
   GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
   SCRIPTS_BASE_URL: https://raw.githubusercontent.com/linksplatform/Scripts/main/MultiProjectRepository
-  
+
 defaults:
   run:
     working-directory: csharp
@@ -19,7 +19,7 @@ jobs:
   test:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v1
+      - uses: actions/checkout@v4
         with:
           submodules: true
       - name: Test
@@ -29,21 +29,20 @@ jobs:
     needs: test
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v1
+      - uses: actions/checkout@v4
         with:
           submodules: true
-      - uses: nuget/setup-nuget@v1
       - name: Publish NuGet package to GitHub Package Registry
         run: |
           dotnet build -c Release
           dotnet pack -c Release
-          nuget source Add -Name "GitHub" -Source "https://nuget.pkg.github.com/linksplatform/index.json" -UserName linksplatform -Password ${{ secrets.GITHUB_TOKEN }}
-          nuget push **/*.nupkg -Source "GitHub" -SkipDuplicate
+          dotnet nuget add source "https://nuget.pkg.github.com/linksplatform/index.json" --name "GitHub" --username linksplatform --password ${{ secrets.GITHUB_TOKEN }} --store-password-in-clear-text
+          dotnet nuget push ./**/*.nupkg --source "GitHub" --skip-duplicate
   pusnToNuget:
     runs-on: ubuntu-latest
     needs: test
     steps:
-    - uses: actions/checkout@v1
+    - uses: actions/checkout@v4
       with:
         submodules: true
     - name: Read project information
@@ -60,7 +59,7 @@ jobs:
     runs-on: ubuntu-latest
     needs: test
     steps:
-      - uses: actions/checkout@v1
+      - uses: actions/checkout@v4
         with:
           submodules: true
       - name: Read project information
@@ -82,12 +81,12 @@ jobs:
     outputs:
       isCsFilesChanged: ${{ steps.setIsCsFilesChangedOutput.outputs.isCsFilesChanged }}
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
       with:
        fetch-depth: 0
     - name: Get changed files using defaults
       id: changed-files
-      uses: tj-actions/changed-files@v21
+      uses: tj-actions/changed-files@v46
     - name: Set output isCsFilesChanged
       id: setIsCsFilesChangedOutput
       run: |
@@ -100,14 +99,14 @@ jobs:
             isCsFilesChanged='true'
           fi
         done
-        echo "::set-output name=isCsFilesChanged::${isCsFilesChanged}"
+        echo "isCsFilesChanged=${isCsFilesChanged}" >> "$GITHUB_OUTPUT"
         echo "isCsFilesChanged: ${isCsFilesChanged}"
   generatePdfWithCode:
     runs-on: ubuntu-latest
     needs: [findChangedCsFiles]
     if: ${{ needs.findChangedCsFiles.outputs.isCsFilesChanged == 'true' }}
     steps:
-    - uses: actions/checkout@v1
+    - uses: actions/checkout@v4
       with:
         submodules: true
     - name: Generate PDF with code
@@ -122,7 +121,7 @@ jobs:
     needs: [findChangedCsFiles]
     if: ${{ needs.findChangedCsFiles.outputs.isCsFilesChanged == 'true' }}
     steps:
-    - uses: actions/checkout@v1
+    - uses: actions/checkout@v4
       with:
         submodules: true
     - name: Publish documentation to gh-pages branch

changelog.d/20260322_000000_fix_unused_import_get_bump_type.md

@@ -0,0 +1,7 @@
+---
+bump: patch
+---
+
+### Fixed
+
+- Removed unused `std::process::exit` import from `scripts/get-bump-type.rs` that caused a compiler warning

docs/case-studies/issue-135/README.md

@@ -0,0 +1,157 @@
+# Case Study: Issue #135 — CI/CD Failures in Rust and C# Pipelines
+
+## Overview
+
+- **Issue:** [#135](https://github.com/linksplatform/Numbers/issues/135)
+- **Failing Runs:**
+  - Rust: [23398717024](https://github.com/linksplatform/Numbers/actions/runs/23398717024)
+  - C#: [23398717023](https://github.com/linksplatform/Numbers/actions/runs/23398717023)
+- **Date:** 2026-03-22
+- **Status:** Root causes identified and fixed.
+
+---
+
+## Timeline / Sequence of Events
+
+1. Commit `bde6c03` was pushed to `main` (merge of PR #134).
+2. Both the Rust CI/CD Pipeline and the C# workflow were triggered.
+3. **Rust:** All jobs passed except **Auto Release** — the "Determine bump type from changelog fragments" step failed.
+4. **C#:** All jobs passed except **pushNuGetPackageToGitHubPackageRegistry** — the `nuget source Add` command failed.
+
+---
+
+## Root Cause Analysis
+
+### Rust CI Failure: Unused Import in get-bump-type.rs
+
+**Primary Root Cause:**
+
+In `scripts/get-bump-type.rs`, line 30 contained:
+
+```rust
+use std::process::exit;
+```
+
+This import is **never used** anywhere in the file. All other scripts that import `exit` do call it; only `get-bump-type.rs` does not.
+
+**Why It Became a Fatal Error:**
+
+The CI workflow (`rust.yml`, line 48) sets:
+
+```yaml
+env:
+  RUSTFLAGS: -Dwarnings
+```
+
+The `-Dwarnings` flag promotes all Rust compiler warnings to errors. The `unused-imports` lint (normally a warning) became a compile error, preventing `rust-script` from building and running the script.
+
+**Fix:** Remove the unused import from `scripts/get-bump-type.rs`.
+
+### C# CI Failure: Mono Not Found on Ubuntu 24.04
+
+**Primary Root Cause:**
+
+The `pushNuGetPackageToGitHubPackageRegistry` job used `nuget/setup-nuget@v1` to install `nuget.exe`, then ran:
+
+```yaml
+nuget source Add -Name "GitHub" -Source "https://nuget.pkg.github.com/linksplatform/index.json" ...
+nuget push **/*.nupkg -Source "GitHub" -SkipDuplicate
+```
+
+On Linux, `nuget.exe` is a .NET Framework executable that requires **Mono** to run. Ubuntu 24.04 GitHub-hosted runners **do not have Mono pre-installed**, resulting in:
+
+```
+/opt/hostedtoolcache/nuget.exe/7.3.0/x64/nuget: 2: mono: not found
+##[error]Process completed with exit code 127.
+```
+
+**How Long This Has Been Broken:**
+
+This same failure occurred in CI run [16390287640](https://github.com/linksplatform/Numbers/actions/runs/16390287640) on **2025-07-19**, confirming the issue has persisted for at least **8 months**.
+
+**Fix:** Replace `nuget.exe` CLI commands with `dotnet nuget` commands, which are part of the .NET SDK already installed on the runner:
+
+```yaml
+# Before (requires Mono):
+- uses: nuget/setup-nuget@v1
+- run: |
+    nuget source Add -Name "GitHub" -Source "..." -UserName ... -Password ...
+    nuget push **/*.nupkg -Source "GitHub" -SkipDuplicate
+
+# After (uses dotnet SDK directly):
+- run: |
+    dotnet nuget add source "..." --name "GitHub" --username ... --password ... --store-password-in-clear-text
+    dotnet nuget push ./**/*.nupkg --source "GitHub" --skip-duplicate
+```
+
+### Additional Issues Fixed in C# Workflow
+
+| Issue | Before | After | Why |
+|-------|--------|-------|-----|
+| Outdated checkout action | `actions/checkout@v1` | `actions/checkout@v4` | v1 is 5+ years old, missing security fixes and features |
+| Outdated changed-files action | `tj-actions/changed-files@v21` | `tj-actions/changed-files@v46` | v21 is outdated, potential security/compatibility issues |
+| Deprecated set-output syntax | `::set-output name=...::` | `>> "$GITHUB_OUTPUT"` | set-output was deprecated in Oct 2022, will be removed |
+| Node.js 20 deprecation | `nuget/setup-nuget@v1` | Removed (not needed) | Node.js 20 actions deprecated, forced to Node.js 24 from June 2026 |
+
+---
+
+## Impact
+
+### Rust
+- Auto Release job blocked on every push to `main`.
+- Automated versioning and crate publishing could not proceed.
+- No production code or tests were affected — only the release automation script.
+
+### C#
+- GitHub Package Registry publishing has been broken since at least July 2025.
+- NuGet.org publishing (`pusnToNuget` job) was **not affected** — it uses `dotnet nuget push` and continued to work.
+- The failure did not block other C# CI jobs (test, release, NuGet.org publish all succeeded).
+
+---
+
+## CI Log Evidence
+
+### Rust (run 23398717024)
+
+From `ci-logs/rust-23398717024.log`:
+
+```
+error: unused import: `std::process::exit`
+  --> /home/runner/work/Numbers/Numbers/scripts/get-bump-type.rs:30:5
+   |
+30 | use std::process::exit;
+   |     ^^^^^^^^^^^^^^^^^^
+   |
+   = note: `-D unused-imports` implied by `-D warnings`
+
+error: could not compile `get-bump-type_412c20687aa3a320be6ee72f` due to 1 previous error
+error: Could not execute cargo
+```
+
+### C# (run 23398717023)
+
+From `ci-logs/csharp-23398717023.log`:
+
+```
+Successfully created package '/home/runner/work/Numbers/Numbers/csharp/Platform.Numbers/bin/Release/Platform.Numbers.0.9.0.nupkg'.
+Successfully created package '/home/runner/work/Numbers/Numbers/csharp/Platform.Numbers/bin/Release/Platform.Numbers.0.9.0.snupkg'.
+/opt/hostedtoolcache/nuget.exe/7.3.0/x64/nuget: 2: mono: not found
+##[error]Process completed with exit code 127.
+```
+
+---
+
+## Additional Notes
+
+### Node.js 20 Deprecation Warnings
+
+Both workflows contained annotations about Node.js 20 actions being deprecated.
+GitHub will force Node.js 24 by default starting **June 2nd, 2026**.
+The C# workflow fix addresses this by removing the `nuget/setup-nuget@v1` dependency
+and updating all actions to their latest versions.
+
+### Possible Future Improvements
+
+1. **Rust:** Consider adding a lint step that compiles all scripts to catch import issues earlier.
+2. **C#:** Consider adding a PR-triggered CI check (currently C# workflow only runs on push to main).
+3. **C#:** The `pusnToNuget` and `publiseRelease` job names contain typos — consider renaming for clarity in a future PR.

scripts/get-bump-type.rs

@@ -27,7 +27,6 @@ use std::env;
 use std::fs;
 use std::io::Write;
 use std::path::Path;
-use std::process::exit;
 use regex::Regex;
 
 fn get_arg(name: &str) -> Option<String> {