refactor: install external providers from module (#2637)

# What does this PR do?

Today, external providers are installed via the `external_providers_dir`
in the config. This necessitates users to understand the `ProviderSpec`
and set up their directories accordingly. This process splits up the
config for the stack across multiple files, directories, and formats.

Most (if not all) external providers today have a
[get_provider_spec](559cb18fbb/src/ramalama_stack/provider.py (L9))
method that sits unused. Utilizing this method rather than the
providers.d route allows for a much easier installation process for
external providers and limits the amount of extra configuration a
regular user has to do to get their stack off the ground.

To accomplish this and wire it throughout the build process, Introduce
the concept of a `module` for users to specify for an external provider
upon build time. In order to facilitate this, align the build and run
spec to use `Provider` class rather than the stringified provider_type
that build currently uses.

For example, say this is in your build config:

```
- provider_id: ramalama
  provider_type: remote::ramalama
  module: ramalama_stack
```

during build (in the various `build_...` scripts), additionally to
installing any pip dependencies we will also install this module and use
the `get_provider_spec` method to retrieve the ProviderSpec that is
currently specified using `providers.d`.

In production so far, providing instructions for installing external
providers for users has been difficult: they need to install the module
as a pre-req, create the providers.d directory, copy in the provider
spec, and also copy in the necessary build/run yaml files. Accessing an
external provider should be as easy as possible, and pointing to its
installable module aligns more with the rest of our build and dependency
management process.

For now, `external_providers_dir` still exists as an alternate more
declarative method of using external providers.

## Test Plan

added an integration test installing an external provider from module
and more unit test coverage for `get_provider_registry`


( the warning in yellow is expected, the module is installed inside of
the build env, not where we are running the command)
<img width="1119" height="400" alt="Screenshot 2025-07-24 at 11 30
48 AM"
src="https://github.com/user-attachments/assets/1efbaf45-b9e8-451a-bd63-264ed664706d"
/>

<img width="1154" height="618" alt="Screenshot 2025-07-24 at 11 31
14 AM"
src="https://github.com/user-attachments/assets/feb2b3ea-c5dd-418e-9662-9a3bd5dd6bdc"
/>

---------

Signed-off-by: Charlie Doern <cdoern@redhat.com>

llama_stack/distribution/build_venv.sh

@@ -18,6 +18,76 @@ UV_HTTP_TIMEOUT=${UV_HTTP_TIMEOUT:-500}
 UV_SYSTEM_PYTHON=${UV_SYSTEM_PYTHON:-}
 VIRTUAL_ENV=${VIRTUAL_ENV:-}
 
+set -euo pipefail
+
+# Define color codes
+RED='\033[0;31m'
+NC='\033[0m' # No Color
+
+SCRIPT_DIR=$(dirname "$(readlink -f "$0")")
+source "$SCRIPT_DIR/common.sh"
+
+# Usage function
+usage() {
+  echo "Usage: $0 --env-name <env_name> --normal-deps <pip_dependencies> [--external-provider-deps <external_provider_deps>] [--optional-deps <special_pip_deps>]"
+  echo "Example: $0 --env-name mybuild --normal-deps 'numpy pandas scipy' --external-provider-deps 'foo' --optional-deps 'bar'"
+  exit 1
+}
+
+# Parse arguments
+env_name=""
+normal_deps=""
+external_provider_deps=""
+optional_deps=""
+
+while [[ $# -gt 0 ]]; do
+  key="$1"
+  case "$key" in
+    --env-name)
+      if [[ -z "$2" || "$2" == --* ]]; then
+        echo "Error: --env-name requires a string value" >&2
+        usage
+      fi
+      env_name="$2"
+      shift 2
+      ;;
+    --normal-deps)
+      if [[ -z "$2" || "$2" == --* ]]; then
+        echo "Error: --normal-deps requires a string value" >&2
+        usage
+      fi
+      normal_deps="$2"
+      shift 2
+      ;;
+    --external-provider-deps)
+      if [[ -z "$2" || "$2" == --* ]]; then
+        echo "Error: --external-provider-deps requires a string value" >&2
+        usage
+      fi
+      external_provider_deps="$2"
+      shift 2
+      ;;
+    --optional-deps)
+      if [[ -z "$2" || "$2" == --* ]]; then
+        echo "Error: --optional-deps requires a string value" >&2
+        usage
+      fi
+      optional_deps="$2"
+      shift 2
+      ;;
+    *)
+      echo "Unknown option: $1" >&2
+      usage
+      ;;
+  esac
+done
+
+# Check required arguments
+if [[ -z "$env_name" || -z "$normal_deps" ]]; then
+  echo "Error: --env-name and --normal-deps are required." >&2
+  usage
+fi
+
 if [ -n "$LLAMA_STACK_DIR" ]; then
   echo "Using llama-stack-dir=$LLAMA_STACK_DIR"
 fi
@@ -25,29 +95,6 @@ if [ -n "$LLAMA_STACK_CLIENT_DIR" ]; then
   echo "Using llama-stack-client-dir=$LLAMA_STACK_CLIENT_DIR"
 fi
 
-if [ "$#" -lt 2 ]; then
-  echo "Usage: $0 <env_name> <pip_dependencies> [<special_pip_deps>]" >&2
-  echo "Example: $0 mybuild ./my-stack-build.yaml 'numpy pandas scipy'" >&2
-  exit 1
-fi
-
-special_pip_deps="$3"
-
-set -euo pipefail
-
-env_name="$1"
-pip_dependencies="$2"
-
-# Define color codes
-RED='\033[0;31m'
-NC='\033[0m' # No Color
-
-# this is set if we actually create a new conda in which case we need to clean up
-ENVNAME=""
-
-SCRIPT_DIR=$(dirname "$(readlink -f "$0")")
-source "$SCRIPT_DIR/common.sh"
-
 # pre-run checks to make sure we can proceed with the installation
 pre_run_checks() {
   local env_name="$1"
@@ -71,49 +118,44 @@ pre_run_checks() {
 }
 
 run() {
-  local env_name="$1"
-  local pip_dependencies="$2"
-  local special_pip_deps="$3"
-
+  # Use only global variables set by flag parser
   if [ -n "$UV_SYSTEM_PYTHON" ] || [ "$env_name" == "__system__" ]; then
     echo "Installing dependencies in system Python environment"
-    # if env == __system__, ensure we set UV_SYSTEM_PYTHON
     export UV_SYSTEM_PYTHON=1
   elif [ "$VIRTUAL_ENV" == "$env_name" ]; then
     echo "Virtual environment $env_name is already active"
   else
     echo "Using virtual environment $env_name"
     uv venv "$env_name"
-    # shellcheck source=/dev/null
     source "$env_name/bin/activate"
   fi
 
   if [ -n "$TEST_PYPI_VERSION" ]; then
-    # these packages are damaged in test-pypi, so install them first
     uv pip install fastapi libcst
-    # shellcheck disable=SC2086
-    # we are building a command line so word splitting is expected
     uv pip install --extra-index-url https://test.pypi.org/simple/ \
       --index-strategy unsafe-best-match \
       llama-stack=="$TEST_PYPI_VERSION" \
-      $pip_dependencies
-    if [ -n "$special_pip_deps" ]; then
-      IFS='#' read -ra parts <<<"$special_pip_deps"
+      $normal_deps
+    if [ -n "$optional_deps" ]; then
+      IFS='#' read -ra parts <<<"$optional_deps"
       for part in "${parts[@]}"; do
         echo "$part"
-        # shellcheck disable=SC2086
-        # we are building a command line so word splitting is expected
         uv pip install $part
       done
     fi
+    if [ -n "$external_provider_deps" ]; then
+      IFS='#' read -ra parts <<<"$external_provider_deps"
+      for part in "${parts[@]}"; do
+        echo "$part"
+        uv pip install "$part"
+      done
+    fi
   else
-    # Re-installing llama-stack in the new virtual environment
     if [ -n "$LLAMA_STACK_DIR" ]; then
       if [ ! -d "$LLAMA_STACK_DIR" ]; then
         printf "${RED}Warning: LLAMA_STACK_DIR is set but directory does not exist: %s${NC}\n" "$LLAMA_STACK_DIR" >&2
         exit 1
       fi
-
       printf "Installing from LLAMA_STACK_DIR: %s\n"  "$LLAMA_STACK_DIR"
       uv pip install --no-cache-dir -e "$LLAMA_STACK_DIR"
     else
@@ -125,27 +167,41 @@ run() {
         printf "${RED}Warning: LLAMA_STACK_CLIENT_DIR is set but directory does not exist: %s${NC}\n" "$LLAMA_STACK_CLIENT_DIR" >&2
         exit 1
       fi
-
       printf "Installing from LLAMA_STACK_CLIENT_DIR: %s\n" "$LLAMA_STACK_CLIENT_DIR"
       uv pip install --no-cache-dir -e "$LLAMA_STACK_CLIENT_DIR"
     fi
 
-    # Install pip dependencies
     printf "Installing pip dependencies\n"
-    # shellcheck disable=SC2086
-    # we are building a command line so word splitting is expected
-    uv pip install $pip_dependencies
-    if [ -n "$special_pip_deps" ]; then
-      IFS='#' read -ra parts <<<"$special_pip_deps"
+    uv pip install $normal_deps
+    if [ -n "$optional_deps" ]; then
+      IFS='#' read -ra parts <<<"$optional_deps"
       for part in "${parts[@]}"; do
-        echo "$part"
-        # shellcheck disable=SC2086
-        # we are building a command line so word splitting is expected
+        echo "Installing special provider module: $part"
         uv pip install $part
       done
     fi
+    if [ -n "$external_provider_deps" ]; then
+      IFS='#' read -ra parts <<<"$external_provider_deps"
+      for part in "${parts[@]}"; do
+        echo "Installing external provider module: $part"
+        uv pip install "$part"
+        echo "Getting provider spec for module: $part and installing dependencies"
+        package_name=$(echo "$part" | sed 's/[<>=!].*//')
+        python3 -c "
+import importlib
+import sys
+try:
+    module = importlib.import_module(f'$package_name.provider')
+    spec = module.get_provider_spec()
+    if hasattr(spec, 'pip_packages') and spec.pip_packages:
+        print('\\n'.join(spec.pip_packages))
+except Exception as e:
+    print(f'Error getting provider spec for $package_name: {e}', file=sys.stderr)
+" | uv pip install -r -
+      done
+    fi
   fi
 }
 
 pre_run_checks "$env_name"
-run "$env_name" "$pip_dependencies" "$special_pip_deps"
+run