initial copy of code from gofmt and go/printer

Author: Randall C. O'Reilly

README.md

@@ -1,2 +1,8 @@
-# gotopy
-Go to Python converter -- translates Go code into Python code
+# GoToPy
+
+GoToPy is a Go to Python converter -- translates Go code into Python code.
+
+It is based on the Go `gofmt` command source code and the go `printer` package, which parses Go files and writes them out according to standard go formatting.
+
+We have modified the `printer` code in the `pyprint` package to instead print out Python code.
+

diff/diff.go

@@ -0,0 +1,58 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package diff implements a Diff function that compare two inputs
+// using the 'diff' tool.
+package diff
+
+import (
+	"io/ioutil"
+	"os"
+	"os/exec"
+	"runtime"
+)
+
+// Returns diff of two arrays of bytes in diff tool format.
+func Diff(prefix string, b1, b2 []byte) ([]byte, error) {
+	f1, err := writeTempFile(prefix, b1)
+	if err != nil {
+		return nil, err
+	}
+	defer os.Remove(f1)
+
+	f2, err := writeTempFile(prefix, b2)
+	if err != nil {
+		return nil, err
+	}
+	defer os.Remove(f2)
+
+	cmd := "diff"
+	if runtime.GOOS == "plan9" {
+		cmd = "/bin/ape/diff"
+	}
+
+	data, err := exec.Command(cmd, "-u", f1, f2).CombinedOutput()
+	if len(data) > 0 {
+		// diff exits with a non-zero status when the files don't match.
+		// Ignore that failure as long as we get output.
+		err = nil
+	}
+	return data, err
+}
+
+func writeTempFile(prefix string, data []byte) (string, error) {
+	file, err := ioutil.TempFile("", prefix)
+	if err != nil {
+		return "", err
+	}
+	_, err = file.Write(data)
+	if err1 := file.Close(); err == nil {
+		err = err1
+	}
+	if err != nil {
+		os.Remove(file.Name())
+		return "", err
+	}
+	return file.Name(), nil
+}

format.go

@@ -0,0 +1,106 @@
+// Copyright 2020 The Go-Python Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// This is based on gofmt source code:
+
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import (
+	"bytes"
+	"go/ast"
+	"go/token"
+
+	"github.com/goki/gotopy/pyprint"
+)
+
+// format formats the given package file originally obtained from src
+// and adjusts the result based on the original source via sourceAdj
+// and indentAdj.
+func format(
+	fset *token.FileSet,
+	file *ast.File,
+	sourceAdj func(src []byte, indent int) []byte,
+	indentAdj int,
+	src []byte,
+	cfg pyprint.Config,
+) ([]byte, error) {
+	if sourceAdj == nil {
+		// Complete source file.
+		var buf bytes.Buffer
+		err := cfg.Fprint(&buf, fset, file)
+		if err != nil {
+			return nil, err
+		}
+		return buf.Bytes(), nil
+	}
+
+	// Partial source file.
+	// Determine and prepend leading space.
+	i, j := 0, 0
+	for j < len(src) && isSpace(src[j]) {
+		if src[j] == '\n' {
+			i = j + 1 // byte offset of last line in leading space
+		}
+		j++
+	}
+	var res []byte
+	res = append(res, src[:i]...)
+
+	// Determine and prepend indentation of first code line.
+	// Spaces are ignored unless there are no tabs,
+	// in which case spaces count as one tab.
+	indent := 0
+	hasSpace := false
+	for _, b := range src[i:j] {
+		switch b {
+		case ' ':
+			hasSpace = true
+		case '\t':
+			indent++
+		}
+	}
+	if indent == 0 && hasSpace {
+		indent = 1
+	}
+	for i := 0; i < indent; i++ {
+		res = append(res, '\t')
+	}
+
+	// Format the source.
+	// Write it without any leading and trailing space.
+	cfg.Indent = indent + indentAdj
+	var buf bytes.Buffer
+	err := cfg.Fprint(&buf, fset, file)
+	if err != nil {
+		return nil, err
+	}
+	out := sourceAdj(buf.Bytes(), cfg.Indent)
+
+	// If the adjusted output is empty, the source
+	// was empty but (possibly) for white space.
+	// The result is the incoming source.
+	if len(out) == 0 {
+		return src, nil
+	}
+
+	// Otherwise, append output to leading space.
+	res = append(res, out...)
+
+	// Determine and append trailing space.
+	i = len(src)
+	for i > 0 && isSpace(src[i-1]) {
+		i--
+	}
+	return append(res, src[i:]...), nil
+}
+
+// isSpace reports whether the byte is a space character.
+// isSpace defines a space as being among the following bytes: ' ', '\t', '\n' and '\r'.
+func isSpace(b byte) bool {
+	return b == ' ' || b == '\t' || b == '\n' || b == '\r'
+}