tsserver - ts.go

     1  // Package tsserver implements a simple wrapper around fs.FS to intercept calls
     2  // to open Javascript files, and instead open their Typescript equivelants and
     3  // generate the Javascript.
     4  package tsserver // import "vimagination.zapto.org/tsserver"
     5  
     6  import (
     7  	"bytes"
     8  	"fmt"
     9  	"io/fs"
    10  	"strings"
    11  
    12  	"vimagination.zapto.org/javascript"
    13  	"vimagination.zapto.org/parser"
    14  )
    15  
    16  const (
    17  	jsExt = ".js"
    18  	tsExt = ".ts"
    19  )
    20  
    21  type wrapped struct {
    22  	fs.FS
    23  }
    24  
    25  // WrapFS takes a fs.FS and intercepts any calls to open .js files, and instead
    26  // generates a file from a similarly named .ts file, if one exists.
    27  //
    28  // If a .ts file does not exists, fails to be converted to javascript, or if the
    29  // file being opened is not a .js file then the file open will not be
    30  // intercepted.
    31  func WrapFS(f fs.FS) fs.FS {
    32  	return &wrapped{FS: f}
    33  }
    34  
    35  func (w *wrapped) Open(name string) (fs.File, error) {
    36  	if strings.HasSuffix(name, jsExt) {
    37  		if tsf, err := w.FS.Open(strings.TrimSuffix(name, jsExt) + tsExt); err == nil {
    38  			if stat, err := tsf.Stat(); err == nil {
    39  				tk := parser.NewReaderTokeniser(tsf)
    40  				m, err := javascript.ParseModule(javascript.AsTypescript(&tk))
    41  				if err == nil {
    42  					var buf bytes.Buffer
    43  					fmt.Fprintf(&buf, "%s", m)
    44  					return &file{
    45  						Reader:   bytes.NewReader(buf.Bytes()),
    46  						name:     name,
    47  						FileInfo: stat,
    48  					}, nil
    49  				}
    50  			}
    51  		}
    52  	}
    53  	return w.FS.Open(name)
    54  }
    55  
    56  type file struct {
    57  	*bytes.Reader
    58  	name string
    59  	fs.FileInfo
    60  }
    61  
    62  func (file) Readdir(count int) ([]fs.FileInfo, error) {
    63  	return nil, fs.ErrInvalid
    64  }
    65  
    66  func (f *file) Stat() (fs.FileInfo, error) {
    67  	return f, nil
    68  }
    69  
    70  func (file) Close() error {
    71  	return nil
    72  }
    73  
    74  func (f *file) Name() string {
    75  	return f.name
    76  }
    77  
    78  func (f *file) Size() int64 {
    79  	return f.Reader.Size()
    80  }
    81