ci: auto-install Flutter from cn mirror

Run 8: Flutter is not on the runner (PATH, FLUTTER_ROOT and common
dirs are all empty). Make the workflow self-contained: if Flutter is
not found, download the pinned 3.41.4 SDK from storage.flutter-io.cn
into a persistent C:\flutter-ci dir (reused on later runs) and add
it to PATH.

.gitea/workflows/ci.yml

@@ -31,32 +31,55 @@ jobs:
       - name: Checkout
         uses: https://gitea.com/actions/checkout@v4
 
-      # The runner's Actions shell often does not inherit Flutter on PATH, so
+      # Ensure Flutter is available. The runner's Actions shell does not have
-      # locate it and add it to PATH for subsequent steps. Set a system env var
+      # Flutter on PATH, so: use it if present (PATH / FLUTTER_ROOT / common
-      # FLUTTER_ROOT to your Flutter SDK dir, or add Flutter's bin to PATH.
+      # dirs), otherwise install the pinned SDK from the flutter-io.cn mirror
-      - name: Locate Flutter
+      # into a persistent dir (C:\flutter-ci) that is reused across runs.
+      - name: Set up Flutter
         shell: powershell
         run: |
+          $ErrorActionPreference = 'Stop'
+          $ProgressPreference = 'SilentlyContinue'
           if (Get-Command flutter -ErrorAction SilentlyContinue) {
             Write-Host "flutter already on PATH"; exit 0
           }
           $candidates = @()
           if ($env:FLUTTER_ROOT) { $candidates += (Join-Path $env:FLUTTER_ROOT 'bin') }
           $candidates += @(
-            'C:\flutter\bin','C:\src\flutter\bin','C:\tools\flutter\bin','C:\dev\flutter\bin',
+            'C:\flutter-ci\flutter\bin','C:\flutter\bin','C:\src\flutter\bin',
-            "$env:USERPROFILE\flutter\bin","$env:USERPROFILE\development\flutter\bin",
+            'C:\tools\flutter\bin','C:\dev\flutter\bin',
-            "$env:LOCALAPPDATA\flutter\bin",'C:\fvm\default\bin'
+            "$env:USERPROFILE\flutter\bin","$env:LOCALAPPDATA\flutter\bin"
           )
-          $found = $null
           foreach ($c in $candidates) {
-            if ($c -and (Test-Path (Join-Path $c 'flutter.bat'))) { $found = $c; break }
+            if ($c -and (Test-Path (Join-Path $c 'flutter.bat'))) {
+              Write-Host "Found Flutter at $c"
+              Add-Content -Path $env:GITHUB_PATH -Value $c
+              exit 0
             }
-          if (-not $found) {
-            Write-Error "Flutter not found on PATH or in common locations. Add Flutter's bin to the runner PATH, or set repo variable FLUTTER_ROOT to your Flutter SDK directory."
-            exit 1
           }
-          Write-Host "Found Flutter at $found"
+          # Install the pinned SDK from the China mirror into a persistent dir.
-          Add-Content -Path $env:GITHUB_PATH -Value $found
+          $root = 'C:\flutter-ci'
+          $bin  = Join-Path $root 'flutter\bin'
+          if (-not (Test-Path (Join-Path $bin 'flutter.bat'))) {
+            $url = 'https://storage.flutter-io.cn/flutter_infra_release/releases/stable/windows/flutter_windows_3.41.4-stable.zip'
+            $zip = Join-Path $env:TEMP 'flutter_sdk.zip'
+            New-Item -ItemType Directory -Force -Path $root | Out-Null
+            Write-Host "Downloading Flutter SDK from $url"
+            $ok = $false
+            for ($i = 1; $i -le 3 -and -not $ok; $i++) {
+              try { Invoke-WebRequest -Uri $url -OutFile $zip -UseBasicParsing; $ok = $true }
+              catch { Write-Host "download attempt $i failed: $_"; Start-Sleep 5 }
+            }
+            if (-not $ok) { Write-Error "Failed to download Flutter SDK"; exit 1 }
+            Write-Host "Extracting to $root (this is slow on first run)"
+            Expand-Archive -Path $zip -DestinationPath $root -Force
+            Remove-Item $zip -Force
+          }
+          if (-not (Test-Path (Join-Path $bin 'flutter.bat'))) {
+            Write-Error "Flutter install failed"; exit 1
+          }
+          Write-Host "Flutter ready at $bin"
+          Add-Content -Path $env:GITHUB_PATH -Value $bin
 
       - name: Flutter version
         run: flutter --version