vpython/spec/resolve.go

// Copyright 2017 The LUCI Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package spec

import (
	"context"
	"fmt"
	"os"
	"path/filepath"

	"go.chromium.org/luci/common/errors"
	"go.chromium.org/luci/common/logging"
	"go.chromium.org/luci/common/system/filesystem"

	"go.chromium.org/luci/vpython/api/vpython"
	"go.chromium.org/luci/vpython/python"
)

// IsUserError is tagged into errors caused by bad user inputs (e.g. modules or
// scripts which don't exist).
var IsUserError = errors.BoolTag{
	Key: errors.NewTagKey("this error occurred due to a user input."),
}

// ResolveSpec resolves the configured environment specification. The resulting
// spec is installed into o's EnvConfig.Spec field.
func ResolveSpec(c context.Context, l *Loader, target python.Target, workDir string) (*vpython.Spec, error) {
	// If there's no target, then we're dropping to an interactive shell
	_, interactive := target.(python.NoTarget)

	// Reading script from stdin or executing code from command line args are
	// the same as no script in that we don't have a source file to key off
	// of to find the spec, so resolve from CWD
	//
	// Executing code from command line args.
	_, isCommandTarget := target.(python.CommandTarget)
	//
	// Reading script from stdin.
	script, isScriptTarget := target.(python.ScriptTarget)
	loadFromStdin := isScriptTarget && (script.Path == "-")

	// If we're loading a module, then we could attempt to find the module and
	// start the search there. But resolving the module path in full generality
	// would be slow and/or complicated. Perhaps we'll revisit in the future,
	// but for now let's just start the search in the CWD, as this is at least
	// a subset of the paths we should search.
	_, isModuleTarget := target.(python.ModuleTarget)

	// We're either dropping to interactive mode, reading a script from stdin or
	// command-line, or loading a module. Regardless, try to resolve the spec
	// from the CWD.
	if interactive || isCommandTarget || loadFromStdin || isModuleTarget {
		spec, path, err := l.LoadForScript(c, workDir, false)
		if err != nil {
			return nil, errors.Annotate(err, "failed to load spec for script: %s", target).Err()
		}
		if spec != nil {
			relpath, err := filepath.Rel(workDir, path)
			if err != nil {
				return nil, errors.Annotate(err, "failed to get relative path for %s", path).Err()
			}

			if interactive {
				fmt.Fprintf(os.Stderr, "Starting interactive mode, loading vpython spec from %s\n", relpath)
			}

			if loadFromStdin {
				fmt.Fprintf(os.Stderr, "Reading from stdin, loading vpython spec from %s\n", relpath)
			}

			return spec, nil
		}
	}

	// If we're running a Python script, assert that the target script exists.
	// Additionally, track whether it's a file or a module (directory).
	isModule := false
	if isScriptTarget {
		logging.Debugf(c, "Resolved Python target script: %s", target)

		// Resolve to absolute script path.
		if err := filesystem.AbsPath(&script.Path); err != nil {
			return nil, errors.Annotate(err, "failed to get absolute path of: %s", target).Err()
		}

		// Confirm that the script path actually exists.
		st, err := os.Stat(script.Path)
		if err != nil {
			return nil, IsUserError.Apply(err)
		}

		// If the script is a directory, then we assume that we're doing a module
		// invocation (__main__.py).
		isModule = st.IsDir()
	}

	// If it's a script, try resolving from filesystem first.
	if isScriptTarget {
		spec, _, err := l.LoadForScript(c, script.Path, isModule)
		if err != nil {
			kind := "script"
			if isModule {
				kind = "module"
			}
			return nil, errors.Annotate(err, "failed to load spec for %s: %s", kind, target).Err()
		}
		if spec != nil {
			return spec, nil
		}
	}

	// If standard resolution doesn't yield a spec, fall back on our default spec.
	logging.Infof(c, "Unable to resolve specification path. Using default specification.")
	return nil, nil
}