fix(scripts): add isolated PyYAML runtime fallback

Author: EnocFlores

scripts/bash/common.sh

@@ -400,8 +400,7 @@ check_dir() { [[ -d "$1" && -n $(ls -A "$1" 2>/dev/null) ]] && echo "  ✓ $2" |
 
 _python3_command() {
     if [[ -n "${SPECKIT_PYTHON:-}" ]] && command -v "$SPECKIT_PYTHON" >/dev/null 2>&1 &&
-        "$SPECKIT_PYTHON" -c 'import sys; raise SystemExit(sys.version_info.major != 3)' >/dev/null 2>&1 &&
-        "$SPECKIT_PYTHON" -c 'import yaml' >/dev/null 2>&1; then
+        "$SPECKIT_PYTHON" -c 'import sys; raise SystemExit(sys.version_info.major != 3)' >/dev/null 2>&1; then
         printf '%s\n' "$SPECKIT_PYTHON"
     elif command -v python3 >/dev/null 2>&1 &&
         python3 -c 'import sys; raise SystemExit(sys.version_info.major != 3)' >/dev/null 2>&1; then
@@ -417,6 +416,28 @@ _python3_command() {
     fi
 }
 
+# SPECKIT_YAML_RUNTIME_FALLBACK=1
+_python3_yaml_command() {
+    if [[ -n "${SPECKIT_PYTHON:-}" ]] && command -v "$SPECKIT_PYTHON" >/dev/null 2>&1 &&
+        PYTHONSAFEPATH=1 "$SPECKIT_PYTHON" -c 'import sys, yaml; raise SystemExit(sys.version_info.major != 3)' >/dev/null 2>&1; then
+        printf '%s\n' "$SPECKIT_PYTHON"
+    elif command -v python3 >/dev/null 2>&1 &&
+        PYTHONSAFEPATH=1 python3 -c 'import sys, yaml; raise SystemExit(sys.version_info.major != 3)' >/dev/null 2>&1; then
+        printf '%s\n' "python3"
+    elif command -v python >/dev/null 2>&1 &&
+        PYTHONSAFEPATH=1 python -c 'import sys, yaml; raise SystemExit(sys.version_info.major != 3)' >/dev/null 2>&1; then
+        printf '%s\n' "python"
+    elif command -v py >/dev/null 2>&1 &&
+        PYTHONSAFEPATH=1 py -3 -c 'import sys, yaml; raise SystemExit(sys.version_info.major != 3)' >/dev/null 2>&1; then
+        printf '%s\n' "py" "-3"
+    elif command -v uv >/dev/null 2>&1 &&
+        PYTHONPATH= PYTHONSAFEPATH=1 uv run --isolated --no-project --with pyyaml==6.0.3 python -c 'import sys, yaml; raise SystemExit(sys.version_info.major != 3)' >/dev/null 2>&1; then
+        printf '%s\n' "uv" "run" "--isolated" "--no-project" "--with" "pyyaml==6.0.3" "python"
+    else
+        return 1
+    fi
+}
+
 _sorted_extension_ids() {
     local ext_dir="$1"
     local -a python_cmd=()
@@ -643,6 +664,8 @@ resolve_template_content() {
         local sorted_presets=""
         local registry_parsed=false
         local -a python_cmd=()
+        local -a yaml_cmd=()
+        local yaml_cmd_resolved=false
         local _python_cmd_line
         while IFS= read -r _python_cmd_line; do
             python_cmd+=("$_python_cmd_line")
@@ -688,15 +711,25 @@ except Exception:
                 local manifest="$presets_dir/$preset_id/preset.yml"
                 local manifest_declared=false
                 if [ -f "$manifest" ]; then
-                    if [ "${#python_cmd[@]}" -eq 0 ]; then
+                    if [ "$yaml_cmd_resolved" = false ]; then
+                        while IFS= read -r _python_cmd_line; do
+                            yaml_cmd+=("$_python_cmd_line")
+                        done < <(_python3_yaml_command)
+                        yaml_cmd_resolved=true
+                    fi
+                    if [ "${#yaml_cmd[@]}" -eq 0 ]; then
                         echo "Error: Python 3 and PyYAML are required to resolve preset template composition" >&2
                         return 2
                     fi
                     local result
                     local py_stderr
                     local parse_status
+                    local -a yaml_env=("PYTHONSAFEPATH=1")
+                    if [ "${yaml_cmd[0]}" = "uv" ]; then
+                        yaml_env+=("PYTHONPATH=")
+                    fi
                     py_stderr=$(mktemp)
-                    if result=$(SPECKIT_MANIFEST="$manifest" SPECKIT_TMPL="$template_name" "${python_cmd[@]}" -c "
+                    if result=$(env "${yaml_env[@]}" PYTHONIOENCODING=utf-8 SPECKIT_MANIFEST="$manifest" SPECKIT_TMPL="$template_name" "${yaml_cmd[@]}" -c "
 import sys, os
 try:
     import yaml

scripts/powershell/common.ps1

@@ -322,10 +322,7 @@ function Format-SpecKitCommand {
 function Get-Python3Command {
     if ($env:SPECKIT_PYTHON -and (Get-Command $env:SPECKIT_PYTHON -ErrorAction SilentlyContinue)) {
         $ver = & $env:SPECKIT_PYTHON --version 2>&1
-        if ($ver -match 'Python 3') {
-            & $env:SPECKIT_PYTHON -c 'import yaml' *> $null
-            if ($LASTEXITCODE -eq 0) { return @($env:SPECKIT_PYTHON) }
-        }
+        if ($ver -match 'Python 3') { return @($env:SPECKIT_PYTHON) }
     }
     if (Get-Command python3 -ErrorAction SilentlyContinue) { return @('python3') }
     if (Get-Command python -ErrorAction SilentlyContinue) {
@@ -339,6 +336,58 @@ function Get-Python3Command {
     return $null
 }
 
+# SPECKIT_YAML_RUNTIME_FALLBACK=1
+function Get-Python3WithYamlCommand {
+    $candidates = @()
+    if ($env:SPECKIT_PYTHON -and (Get-Command $env:SPECKIT_PYTHON -ErrorAction SilentlyContinue)) {
+        $candidates += ,@($env:SPECKIT_PYTHON)
+    }
+    if (Get-Command python3 -ErrorAction SilentlyContinue) { $candidates += ,@('python3') }
+    if (Get-Command python -ErrorAction SilentlyContinue) { $candidates += ,@('python') }
+    if (Get-Command py -ErrorAction SilentlyContinue) { $candidates += ,@('py', '-3') }
+    if (Get-Command uv -ErrorAction SilentlyContinue) {
+        $candidates += ,@(
+            'uv',
+            'run',
+            '--isolated',
+            '--no-project',
+            '--with',
+            'pyyaml==6.0.3',
+            'python'
+        )
+    }
+
+    $previousPythonPath = $env:PYTHONPATH
+    $previousPythonSafePath = $env:PYTHONSAFEPATH
+    try {
+        $env:PYTHONSAFEPATH = '1'
+        foreach ($command in $candidates) {
+            if ($command[0] -eq 'uv') {
+                Remove-Item Env:PYTHONPATH -ErrorAction SilentlyContinue
+            } elseif ($null -eq $previousPythonPath) {
+                Remove-Item Env:PYTHONPATH -ErrorAction SilentlyContinue
+            } else {
+                $env:PYTHONPATH = $previousPythonPath
+            }
+            [array]$commandArgs = if ($command.Count -gt 1) { $command[1..($command.Count - 1)] } else { @() }
+            & $command[0] @commandArgs -c 'import sys, yaml; raise SystemExit(sys.version_info.major != 3)' *> $null
+            if ($LASTEXITCODE -eq 0) { return $command }
+        }
+    } finally {
+        if ($null -eq $previousPythonPath) {
+            Remove-Item Env:PYTHONPATH -ErrorAction SilentlyContinue
+        } else {
+            $env:PYTHONPATH = $previousPythonPath
+        }
+        if ($null -eq $previousPythonSafePath) {
+            Remove-Item Env:PYTHONSAFEPATH -ErrorAction SilentlyContinue
+        } else {
+            $env:PYTHONSAFEPATH = $previousPythonSafePath
+        }
+    }
+    return $null
+}
+
 function Get-NormalizedPriority {
     param($Value)
 
@@ -598,22 +647,34 @@ function Resolve-TemplateContent {
                 ForEach-Object { $_.Name }
         }
 
-        $pyCmd = @(Get-Python3Command)
+        $yamlCmd = $null
+        $yamlCommandResolved = $false
         foreach ($presetId in $sortedPresets) {
                 # Read strategy and file path from preset manifest
                 $strategy = 'replace'
                 $manifestFilePath = ''
                 $manifestDeclared = $false
                 $manifest = Join-Path $presetsDir "$presetId/preset.yml"
-                if ((Test-Path $manifest) -and -not $pyCmd) {
-                    throw "Python 3 and PyYAML are required to resolve preset template composition"
-                }
                 if (Test-Path $manifest) {
+                    if (-not $yamlCommandResolved) {
+                        $yamlCmd = @(Get-Python3WithYamlCommand)
+                        $yamlCommandResolved = $true
+                    }
+                    if (-not $yamlCmd) {
+                        throw "Python 3 and PyYAML are required to resolve preset template composition"
+                    }
                     try {
                         # Use Python to parse YAML manifest for strategy and file path
-                        $pyArgs = if ($pyCmd.Count -gt 1) { $pyCmd[1..($pyCmd.Count-1)] } else { @() }
+                        [array]$pyArgs = if ($yamlCmd.Count -gt 1) { $yamlCmd[1..($yamlCmd.Count-1)] } else { @() }
                         $pyStderrFile = [System.IO.Path]::GetTempFileName()
-                        $stratResult = & $pyCmd[0] @pyArgs -c @"
+                        $previousPythonPath = $env:PYTHONPATH
+                        $previousPythonSafePath = $env:PYTHONSAFEPATH
+                        try {
+                            $env:PYTHONSAFEPATH = '1'
+                            if ($yamlCmd[0] -eq 'uv') {
+                                Remove-Item Env:PYTHONPATH -ErrorAction SilentlyContinue
+                            }
+                            $stratResult = & $yamlCmd[0] @pyArgs -c @"
 import sys
 try:
     import yaml
@@ -668,8 +729,21 @@ except Exception as exc:
     print(f'manifest_invalid: {exc}', file=sys.stderr)
     sys.exit(3)
 "@ $manifest $TemplateName 2>$pyStderrFile
-                        if ($LASTEXITCODE -ne 0) {
-                            if ($LASTEXITCODE -eq 2) {
+                            $parserExitCode = $LASTEXITCODE
+                        } finally {
+                            if ($null -eq $previousPythonPath) {
+                                Remove-Item Env:PYTHONPATH -ErrorAction SilentlyContinue
+                            } else {
+                                $env:PYTHONPATH = $previousPythonPath
+                            }
+                            if ($null -eq $previousPythonSafePath) {
+                                Remove-Item Env:PYTHONSAFEPATH -ErrorAction SilentlyContinue
+                            } else {
+                                $env:PYTHONSAFEPATH = $previousPythonSafePath
+                            }
+                        }
+                        if ($parserExitCode -ne 0) {
+                            if ($parserExitCode -eq 2) {
                                 throw "PyYAML is required to resolve preset template composition"
                             }
                             throw "Invalid preset manifest $manifest"

scripts/powershell/resolve-template.ps1

@@ -22,7 +22,12 @@ if (-not $TemplateName) {
 . "$PSScriptRoot/common.ps1"
 
 $repoRoot = Get-RepoRoot
-$templateContent = Resolve-TemplateContent -TemplateName $TemplateName -RepoRoot $repoRoot
+try {
+    $templateContent = Resolve-TemplateContent -TemplateName $TemplateName -RepoRoot $repoRoot
+} catch {
+    [Console]::Error.WriteLine("ERROR: $($_.Exception.Message)")
+    exit 1
+}
 if ($null -eq $templateContent) {
     [Console]::Error.WriteLine("ERROR: Could not resolve required $TemplateName from the template override stack for $repoRoot")
     exit 1