142 lines
3.5 KiB
Go
142 lines
3.5 KiB
Go
package compose
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import (
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"fmt"
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"io"
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"strings"
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"github.com/tkw1536/pkglib/collection"
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)
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const (
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EnvFileHeader = "# This file is automatically created and updated by the distillery; DO NOT EDIT.\n\n"
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EnvEqualChar = '=' // assignment
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EnvReplaceChar = '#' // replacement for invalid characters
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EnvEscapeChar = '\\' // escaping
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EnvQuoteChar = '"' // quoting
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)
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type errInvalidName string
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func (ei errInvalidName) Error() string {
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return fmt.Sprintf("invalid variable name: %q", string(ei))
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}
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// WriteEnvFile writes a .env file to io.Writer.
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// Variables are written in consistent order.
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//
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// Variable names may only contain ascii letters, numbers or the character "_".
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// Invalid variable names are an error.
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//
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// Variables values are escaped using EscapeEnvValue.
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//
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// count contains the number of bytes written to writer.
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// In case of an error, partial content may already have been written to writer, as indicated by count.
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func WriteEnvFile(writer io.Writer, env map[string]string) (count int, err error) {
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var n int
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// write the header to the file
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n, err = fmt.Fprint(writer, EnvFileHeader)
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count += n
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if err != nil {
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return
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}
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collection.IterateSorted(env, func(key, value string) {
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// if we already had an error, break
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if err != nil {
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return
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}
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// if we don't have a valid name, break
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if !isValidVariable(key) {
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err = errInvalidName(key)
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return
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}
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// write write key = EscapeEnvValue(value) followed by a new line
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n, err = fmt.Fprintf(writer, "%s%s%s\n", key, string(EnvEqualChar), EscapeEnvValue(value))
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count += n
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if err != nil {
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return
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}
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})
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return
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}
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// isValidVariable checks if name is a valid variable name.
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func isValidVariable(name string) bool {
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for _, r := range name {
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if !(r == '_' || (r >= 'a' && r <= 'z') || (r >= 'A' && r <= 'Z') || (r >= '0' && r <= '9')) {
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return false
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}
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}
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return true
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}
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// Escape escapes the given value to be written to an environment variable.
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// If the value does not need escaping, it may return it unchanged.
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//
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// EscapeEnvValue allows ASCII characters from ' ' to '~' (inclusive) as well as '\t', '\r', '\n'.
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// Other characters are automatically replaced by EnvReplaceChar.
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func EscapeEnvValue(value string) (escaped string) {
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// first check if we need to escape at all.
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var changed bool
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for _, r := range value {
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if !isValidEnvChar(r) || r == '\n' || r == '\r' || r == '\t' || r == '$' || r == EnvEscapeChar || r == EnvQuoteChar {
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changed = true
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}
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}
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if !changed {
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return value
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}
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// make a new builder and make space for the original value
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var builder strings.Builder
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builder.Grow(len(value) + 2)
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// begin the quoting
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builder.WriteRune(EnvQuoteChar)
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// iterate over it
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for _, r := range value {
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// if the character is invalid, it is replaced with an '_'
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if !isValidEnvChar(r) {
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builder.WriteRune(EnvReplaceChar)
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continue
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}
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switch r {
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// custom escape for '\n', '\r', '\t'
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case '\n':
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builder.WriteRune(EnvEscapeChar)
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builder.WriteRune('n')
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case '\r':
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builder.WriteRune(EnvEscapeChar)
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builder.WriteRune('r')
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case '\t':
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builder.WriteRune(EnvEscapeChar)
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builder.WriteRune('t')
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// standard escape for special characters
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case '$', EnvEscapeChar, EnvQuoteChar:
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builder.WriteRune(EnvEscapeChar)
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fallthrough
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// that's it
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default:
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builder.WriteRune(r)
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}
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}
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// close the quote
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builder.WriteRune(EnvQuoteChar)
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return builder.String()
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}
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// isValidEnvChar checks if the rune r is allowed in environment variables.
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func isValidEnvChar(r rune) bool {
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return r == '\n' || r == '\r' || r == '\t' || (r >= ' ' && r <= '~')
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}
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