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move parsing key-value files to a separate package
Move the code for parsing key-value files, such as used for env-files and label-files to a separate package. This allows other projects (such as compose) to use the same parsing logic, but provide custom lookup functions for their situation (which is slightly different). The new package provides utilities for parsing key-value files for either a file or an io.Reader. Most tests for EnvFile were now testing functionality that's already tested in the new package, so were (re)moved. Co-authored-by: Nicolas De Loof <[email protected]> Signed-off-by: Nicolas De Loof <[email protected]> Signed-off-by: Sebastiaan van Stijn <[email protected]>
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,130 @@ | ||
| // Package kvfile provides utilities to parse line-delimited key/value files | ||
| // such as used for label-files and env-files. | ||
| // | ||
| // # File format | ||
| // | ||
| // key/value files use the following syntax: | ||
| // | ||
| // - File must be valid UTF-8. | ||
| // - BOM headers are removed. | ||
| // - Leading whitespace is removed for each line. | ||
| // - Lines starting with "#" are ignored. | ||
| // - Empty lines are ignored. | ||
| // - Key/Value pairs are provided as "KEY[=<VALUE>]". | ||
| // - Maximum line-length is limited to [bufio.MaxScanTokenSize]. | ||
| // | ||
| // # Interpolation, substitution, and escaping | ||
| // | ||
| // Both keys and values are used as-is; no interpolation, substitution or | ||
| // escaping is supported, and quotes are considered part of the key or value. | ||
| // Whitespace in values (including leading and trailing) is preserved. Given | ||
| // that the file format is line-delimited, neither key, nor value, can contain | ||
| // newlines. | ||
| // | ||
| // # Key/Value pairs | ||
| // | ||
| // Key/Value pairs take the following format: | ||
| // | ||
| // KEY[=<VALUE>] | ||
| // | ||
| // KEY is required and may not contain whitespaces or NUL characters. Any | ||
| // other character (except for the "=" delimiter) are accepted, but it is | ||
| // recommended to use a subset of the POSIX portable character set, as | ||
| // outlined in [Environment Variables]. | ||
| // | ||
| // VALUE is optional, but may be empty. If no value is provided (i.e., no | ||
| // equal sign ("=") is present), the KEY is omitted in the result, but some | ||
| // functions accept a lookup-function to provide a default value for the | ||
| // given key. | ||
| // | ||
| // [Environment Variables]: https://pubs.opengroup.org/onlinepubs/7908799/xbd/envvar.html | ||
| package kvfile | ||
|
|
||
| import ( | ||
| "bufio" | ||
| "bytes" | ||
| "fmt" | ||
| "io" | ||
| "os" | ||
| "strings" | ||
| "unicode" | ||
| "unicode/utf8" | ||
| ) | ||
|
|
||
| // Parse parses a line-delimited key/value pairs separated by equal sign. | ||
| // It accepts a lookupFn to lookup default values for keys that do not define | ||
| // a value. An error is produced if parsing failed, the content contains invalid | ||
| // UTF-8 characters, or a key contains whitespaces. | ||
| func Parse(filename string, lookupFn func(key string) (value string, found bool)) ([]string, error) { | ||
| fh, err := os.Open(filename) | ||
| if err != nil { | ||
| return []string{}, err | ||
| } | ||
| out, err := parseKeyValueFile(fh, lookupFn) | ||
| _ = fh.Close() | ||
| if err != nil { | ||
| return []string{}, fmt.Errorf("invalid env file (%s): %v", filename, err) | ||
| } | ||
| return out, nil | ||
| } | ||
|
|
||
| // ParseFromReader parses a line-delimited key/value pairs separated by equal sign. | ||
| // It accepts a lookupFn to lookup default values for keys that do not define | ||
| // a value. An error is produced if parsing failed, the content contains invalid | ||
| // UTF-8 characters, or a key contains whitespaces. | ||
| func ParseFromReader(r io.Reader, lookupFn func(key string) (value string, found bool)) ([]string, error) { | ||
| return parseKeyValueFile(r, lookupFn) | ||
| } | ||
|
|
||
| const whiteSpaces = " \t" | ||
|
|
||
| func parseKeyValueFile(r io.Reader, lookupFn func(string) (string, bool)) ([]string, error) { | ||
| lines := []string{} | ||
| scanner := bufio.NewScanner(r) | ||
| utf8bom := []byte{0xEF, 0xBB, 0xBF} | ||
| for currentLine := 1; scanner.Scan(); currentLine++ { | ||
| scannedBytes := scanner.Bytes() | ||
| if !utf8.Valid(scannedBytes) { | ||
| return []string{}, fmt.Errorf("invalid utf8 bytes at line %d: %v", currentLine, scannedBytes) | ||
| } | ||
| // We trim UTF8 BOM | ||
| if currentLine == 1 { | ||
| scannedBytes = bytes.TrimPrefix(scannedBytes, utf8bom) | ||
| } | ||
| // trim the line from all leading whitespace first. trailing whitespace | ||
| // is part of the value, and is kept unmodified. | ||
| line := strings.TrimLeftFunc(string(scannedBytes), unicode.IsSpace) | ||
|
|
||
| if len(line) == 0 || line[0] == '#' { | ||
| // skip empty lines and comments (lines starting with '#') | ||
| continue | ||
| } | ||
|
|
||
| key, _, hasValue := strings.Cut(line, "=") | ||
| if len(key) == 0 { | ||
| return []string{}, fmt.Errorf("no variable name on line '%s'", line) | ||
| } | ||
|
|
||
| // leading whitespace was already removed from the line, but | ||
| // variables are not allowed to contain whitespace or have | ||
| // trailing whitespace. | ||
| if strings.ContainsAny(key, whiteSpaces) { | ||
| return []string{}, fmt.Errorf("variable '%s' contains whitespaces", key) | ||
| } | ||
|
|
||
| if hasValue { | ||
| // key/value pair is valid and has a value; add the line as-is. | ||
| lines = append(lines, line) | ||
| continue | ||
| } | ||
|
|
||
| if lookupFn != nil { | ||
| // No value given; try to look up the value. The value may be | ||
| // empty but if no value is found, the key is omitted. | ||
| if value, found := lookupFn(line); found { | ||
| lines = append(lines, key+"="+value) | ||
| } | ||
| } | ||
| } | ||
| return lines, scanner.Err() | ||
| } |
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