LSP-server-example

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// //nolint
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// Copyright 2023 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package protocol
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// This file declares URI, DocumentURI, and its methods.
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//
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// For the LSP definition of these types, see
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// https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#uri
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import (
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	"fmt"
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	"net/url"
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	"path/filepath"
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	"strings"
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	"unicode"
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)
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// A DocumentURI is the URI of a client editor document.
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//
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// According to the LSP specification:
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//
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//	Care should be taken to handle encoding in URIs. For
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//	example, some clients (such as VS Code) may encode colons
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//	in drive letters while others do not. The URIs below are
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//	both valid, but clients and servers should be consistent
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//	with the form they use themselves to ensure the other party
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//	doesn’t interpret them as distinct URIs. Clients and
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//	servers should not assume that each other are encoding the
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//	same way (for example a client encoding colons in drive
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//	letters cannot assume server responses will have encoded
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//	colons). The same applies to casing of drive letters - one
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//	party should not assume the other party will return paths
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//	with drive letters cased the same as it.
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//
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//	file:///c:/project/readme.md
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//	file:///C%3A/project/readme.md
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//
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// This is done during JSON unmarshalling;
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// see [DocumentURI.UnmarshalText] for details.
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type DocumentURI string
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// A URI is an arbitrary URL (e.g. https), not necessarily a file.
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type URI = string
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// UnmarshalText implements decoding of DocumentURI values.
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//
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// In particular, it implements a systematic correction of various odd
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// features of the definition of DocumentURI in the LSP spec that
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// appear to be workarounds for bugs in VS Code. For example, it may
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// URI-encode the URI itself, so that colon becomes %3A, and it may
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// send file://foo.go URIs that have two slashes (not three) and no
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// hostname.
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//
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// We use UnmarshalText, not UnmarshalJSON, because it is called even
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// for non-addressable values such as keys and values of map[K]V,
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// where there is no pointer of type *K or *V on which to call
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// UnmarshalJSON. (See Go issue #28189 for more detail.)
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//
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// Non-empty DocumentURIs are valid "file"-scheme URIs.
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// The empty DocumentURI is valid.
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func (uri *DocumentURI) UnmarshalText(data []byte) (err error) {
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	*uri, err = ParseDocumentURI(string(data))
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	return
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}
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// Path returns the file path for the given URI.
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//
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// DocumentURI("").Path() returns the empty string.
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//
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// Path panics if called on a URI that is not a valid filename.
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func (uri DocumentURI) Path() string {
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	filename, err := filename(uri)
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	if err != nil {
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		// e.g. ParseRequestURI failed.
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		//
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		// This can only affect DocumentURIs created by
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		// direct string manipulation; all DocumentURIs
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		// received from the client pass through
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		// ParseRequestURI, which ensures validity.
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		panic(err)
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	}
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	return filepath.FromSlash(filename)
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}
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// Dir returns the URI for the directory containing the receiver.
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func (uri DocumentURI) Dir() DocumentURI {
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	// This function could be more efficiently implemented by avoiding any call
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	// to Path(), but at least consolidates URI manipulation.
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	return URIFromPath(filepath.Dir(uri.Path()))
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}
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// Encloses reports whether uri's path, considered as a sequence of segments,
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// is a prefix of file's path.
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func (uri DocumentURI) Encloses(file DocumentURI) bool {
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	return InDir(uri.Path(), file.Path())
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}
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func filename(uri DocumentURI) (string, error) {
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	if uri == "" {
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		return "", nil
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	}
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	// This conservative check for the common case
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	// of a simple non-empty absolute POSIX filename
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	// avoids the allocation of a net.URL.
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	if strings.HasPrefix(string(uri), "file:///") {
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		rest := string(uri)[len("file://"):] // leave one slash
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		for i := 0; i < len(rest); i++ {
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			b := rest[i]
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			// Reject these cases:
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			if b < ' ' || b == 0x7f || // control character
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				b == '%' || b == '+' || // URI escape
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				b == ':' || // Windows drive letter
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				b == '@' || b == '&' || b == '?' { // authority or query
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				goto slow
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			}
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		}
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		return rest, nil
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	}
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slow:
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	u, err := url.ParseRequestURI(string(uri))
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	if err != nil {
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		return "", err
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	}
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	if u.Scheme != fileScheme {
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		return "", fmt.Errorf("only file URIs are supported, got %q from %q", u.Scheme, uri)
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	}
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	// If the URI is a Windows URI, we trim the leading "/" and uppercase
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	// the drive letter, which will never be case sensitive.
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	if isWindowsDriveURIPath(u.Path) {
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		u.Path = strings.ToUpper(string(u.Path[1])) + u.Path[2:]
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	}
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	return u.Path, nil
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}
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// ParseDocumentURI interprets a string as a DocumentURI, applying VS
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// Code workarounds; see [DocumentURI.UnmarshalText] for details.
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func ParseDocumentURI(s string) (DocumentURI, error) {
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	if s == "" {
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		return "", nil
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	}
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	if !strings.HasPrefix(s, "file://") {
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		return "", fmt.Errorf("DocumentURI scheme is not 'file': %s", s)
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	}
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	// VS Code sends URLs with only two slashes,
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	// which are invalid. golang/go#39789.
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	if !strings.HasPrefix(s, "file:///") {
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		s = "file:///" + s[len("file://"):]
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	}
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	// Even though the input is a URI, it may not be in canonical form. VS Code
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	// in particular over-escapes :, @, etc. Unescape and re-encode to canonicalize.
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	path, err := url.PathUnescape(s[len("file://"):])
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	if err != nil {
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		return "", err
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	}
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	// File URIs from Windows may have lowercase drive letters.
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	// Since drive letters are guaranteed to be case insensitive,
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	// we change them to uppercase to remain consistent.
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	// For example, file:///c:/x/y/z becomes file:///C:/x/y/z.
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	if isWindowsDriveURIPath(path) {
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		path = path[:1] + strings.ToUpper(string(path[1])) + path[2:]
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	}
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	u := url.URL{Scheme: fileScheme, Path: path}
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	return DocumentURI(u.String()), nil
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}
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// URIFromPath returns DocumentURI for the supplied file path.
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// Given "", it returns "".
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func URIFromPath(path string) DocumentURI {
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	if path == "" {
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		return ""
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	}
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	if !isWindowsDrivePath(path) {
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		if abs, err := filepath.Abs(path); err == nil {
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			path = abs
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		}
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	}
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	// Check the file path again, in case it became absolute.
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	if isWindowsDrivePath(path) {
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		path = "/" + strings.ToUpper(string(path[0])) + path[1:]
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	}
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	path = filepath.ToSlash(path)
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	u := url.URL{
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		Scheme: fileScheme,
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		Path:   path,
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	}
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	return DocumentURI(u.String())
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}
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const fileScheme = "file"
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// isWindowsDrivePath returns true if the file path is of the form used by
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// Windows. We check if the path begins with a drive letter, followed by a ":".
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// For example: C:/x/y/z.
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func isWindowsDrivePath(path string) bool {
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	if len(path) < 3 {
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		return false
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	}
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	return unicode.IsLetter(rune(path[0])) && path[1] == ':'
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}
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// isWindowsDriveURIPath returns true if the file URI is of the format used by
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// Windows URIs. The url.Parse package does not specially handle Windows paths
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// (see golang/go#6027), so we check if the URI path has a drive prefix (e.g. "/C:").
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func isWindowsDriveURIPath(uri string) bool {
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	if len(uri) < 4 {
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		return false
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	}
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	return uri[0] == '/' && unicode.IsLetter(rune(uri[1])) && uri[2] == ':'
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}
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