oraios/serena · error · FileNotFoundError

yaml-language-server executable not found at {yaml_executabl

Error message

yaml-language-server executable not found at {yaml_executable_path}, something went wrong with the installation.

What it means

Thrown as FileNotFoundError when, after attempting deps.install for the yaml-language-server npm package, the yaml-language-server executable still does not exist at yaml_executable_path. It is a post-install sanity check before building the launch command.

Source

Thrown at src/solidlsp/language_servers/yaml_language_server.py:106

            ls_dirname = (
                "yaml-lsp"
                if yaml_language_server_version == INITIAL_YAML_LANGUAGE_SERVER_VERSION
                else f"yaml-lsp-{yaml_language_server_version}"
            )
            yaml_ls_dir = os.path.join(self._ls_resources_dir, ls_dirname)
            yaml_executable_path = os.path.join(yaml_ls_dir, "node_modules", ".bin", "yaml-language-server")

            # Handle Windows executable extension
            if os.name == "nt":
                yaml_executable_path += ".cmd"

            if not os.path.exists(yaml_executable_path):
                log.info(f"YAML Language Server executable not found at {yaml_executable_path}. Installing...")
                deps.install(yaml_ls_dir)
                log.info("YAML language server dependencies installed successfully")

            if not os.path.exists(yaml_executable_path):
                raise FileNotFoundError(
                    f"yaml-language-server executable not found at {yaml_executable_path}, something went wrong with the installation."
                )

            return yaml_executable_path

        def _create_launch_command(self, core_path: str) -> list[str]:
            return [core_path, "--stdio"]

    def _create_base_initialize_params(self) -> dict:
        """
        Returns the initialize params for the YAML Language Server.
        """
        initialize_params = {
            "locale": "en",
            "capabilities": {
                "textDocument": {
                    "synchronization": {"didSave": True, "dynamicRegistration": True},
                    "completion": {"dynamicRegistration": True, "completionItem": {"snippetSupport": True}},

View on GitHub (pinned to 7fcbca7e62)

Solutions

Delete the yaml language server install directory and rerun to force a clean install.
Run npm install -g yaml-language-server manually and inspect npm errors.
Verify Node.js and npm are installed and on PATH.
Check proxy/registry settings and free disk space.
Pre-install and configure ls_path to the global yaml-language-server binary.

Example fix

// before
ls = SolidLSP("yaml", "/repo")  # auto-install fails silently behind proxy
// after
# export HTTPS_PROXY=http://proxy:8080
# npm install -g yaml-language-server
ls = SolidLSP("yaml", "/repo")  # finds existing install / installs cleanly

Defensive patterns

Strategy: try-catch

Validate before calling

import os
if not os.path.isfile(expected_yaml_ls_path):
    subprocess.run(["npm", "install", "-g", "yaml-language-server"], check=True)

Type guard

def is_executable_file(path: str) -> bool:
    return os.path.isfile(path) and os.access(path, os.X_OK)

Try / catch

try:
    ls = SolidLSP("yaml", repo_path)
except FileNotFoundError as e:
    if "yaml-language-server executable not found" in str(e):
        shutil.rmtree(yaml_ls_install_dir, ignore_errors=True)
        subprocess.run(["npm", "install", "-g", "yaml-language-server"], check=True)
        ls = SolidLSP("yaml", repo_path)
    else:
        raise

Prevention

Pre-install yaml-language-server globally in CI images.
Ensure Node.js/npm are installed before first use.
Clean partial installs from interrupted runs.
Set proxy/registry env vars so npm installs succeed.

When it happens

Trigger: _get_or_install_core_dependency logs 'Installing...', runs deps.install(yaml_ls_dir), then the second os.path.exists check fails.

Common situations: npm install failing behind proxy/firewall; corrupt or partial node_modules from a prior interrupted install; insufficient permissions or disk space in the install dir; Node/npm not installed so the install is a no-op or fails.

Related errors

AI-assisted analysis of oraios/serena@7fcbca7e62 (2026-08-29). Data as JSON: /api/errors/6650e1494408872a. Report an issue: GitHub.