prometheus/promql/parser/lex.go
Ben Kochie 269e7c8091
Fix golint issues.
Signed-off-by: Ben Kochie <superq@gmail.com>
2020-03-23 20:38:43 +01:00

815 lines
19 KiB
Go

// Copyright 2015 The Prometheus Authors
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package parser
import (
"fmt"
"strings"
"unicode"
"unicode/utf8"
)
// Item represents a token or text string returned from the scanner.
type Item struct {
Typ ItemType // The type of this Item.
Pos Pos // The starting position, in bytes, of this Item in the input string.
Val string // The value of this Item.
}
// String returns a descriptive string for the Item.
func (i Item) String() string {
switch {
case i.Typ == EOF:
return "EOF"
case i.Typ == ERROR:
return i.Val
case i.Typ == IDENTIFIER || i.Typ == METRIC_IDENTIFIER:
return fmt.Sprintf("%q", i.Val)
case i.Typ.IsKeyword():
return fmt.Sprintf("<%s>", i.Val)
case i.Typ.IsOperator():
return fmt.Sprintf("<op:%s>", i.Val)
case i.Typ.IsAggregator():
return fmt.Sprintf("<aggr:%s>", i.Val)
case len(i.Val) > 10:
return fmt.Sprintf("%.10q...", i.Val)
}
return fmt.Sprintf("%q", i.Val)
}
// isOperator returns true if the Item corresponds to a arithmetic or set operator.
// Returns false otherwise.
func (i ItemType) IsOperator() bool { return i > operatorsStart && i < operatorsEnd }
// isAggregator returns true if the Item belongs to the aggregator functions.
// Returns false otherwise
func (i ItemType) IsAggregator() bool { return i > aggregatorsStart && i < aggregatorsEnd }
// isAggregator returns true if the Item is an aggregator that takes a parameter.
// Returns false otherwise
func (i ItemType) IsAggregatorWithParam() bool {
return i == TOPK || i == BOTTOMK || i == COUNT_VALUES || i == QUANTILE
}
// isKeyword returns true if the Item corresponds to a keyword.
// Returns false otherwise.
func (i ItemType) IsKeyword() bool { return i > keywordsStart && i < keywordsEnd }
// IsComparisonOperator returns true if the Item corresponds to a comparison operator.
// Returns false otherwise.
func (i ItemType) IsComparisonOperator() bool {
switch i {
case EQL, NEQ, LTE, LSS, GTE, GTR:
return true
default:
return false
}
}
// isSetOperator returns whether the Item corresponds to a set operator.
func (i ItemType) IsSetOperator() bool {
switch i {
case LAND, LOR, LUNLESS:
return true
}
return false
}
type ItemType int
// This is a list of all keywords in PromQL.
// When changing this list, make sure to also change
// the maybe_label grammar rule in the generated parser
// to avoid misinterpretation of labels as keywords.
var key = map[string]ItemType{
// Operators.
"and": LAND,
"or": LOR,
"unless": LUNLESS,
// Aggregators.
"sum": SUM,
"avg": AVG,
"count": COUNT,
"min": MIN,
"max": MAX,
"stddev": STDDEV,
"stdvar": STDVAR,
"topk": TOPK,
"bottomk": BOTTOMK,
"count_values": COUNT_VALUES,
"quantile": QUANTILE,
// Keywords.
"offset": OFFSET,
"by": BY,
"without": WITHOUT,
"on": ON,
"ignoring": IGNORING,
"group_left": GROUP_LEFT,
"group_right": GROUP_RIGHT,
"bool": BOOL,
}
// ItemTypeStr is the default string representations for common Items. It does not
// imply that those are the only character sequences that can be lexed to such an Item.
var ItemTypeStr = map[ItemType]string{
LEFT_PAREN: "(",
RIGHT_PAREN: ")",
LEFT_BRACE: "{",
RIGHT_BRACE: "}",
LEFT_BRACKET: "[",
RIGHT_BRACKET: "]",
COMMA: ",",
ASSIGN: "=",
COLON: ":",
SEMICOLON: ";",
BLANK: "_",
TIMES: "x",
SPACE: "<space>",
SUB: "-",
ADD: "+",
MUL: "*",
MOD: "%",
DIV: "/",
EQL: "==",
NEQ: "!=",
LTE: "<=",
LSS: "<",
GTE: ">=",
GTR: ">",
EQL_REGEX: "=~",
NEQ_REGEX: "!~",
POW: "^",
}
func init() {
// Add keywords to Item type strings.
for s, ty := range key {
ItemTypeStr[ty] = s
}
// Special numbers.
key["inf"] = NUMBER
key["nan"] = NUMBER
}
func (i ItemType) String() string {
if s, ok := ItemTypeStr[i]; ok {
return s
}
return fmt.Sprintf("<Item %d>", i)
}
func (i Item) desc() string {
if _, ok := ItemTypeStr[i.Typ]; ok {
return i.String()
}
if i.Typ == EOF {
return i.Typ.desc()
}
return fmt.Sprintf("%s %s", i.Typ.desc(), i)
}
func (i ItemType) desc() string {
switch i {
case ERROR:
return "error"
case EOF:
return "end of input"
case COMMENT:
return "comment"
case IDENTIFIER:
return "identifier"
case METRIC_IDENTIFIER:
return "metric identifier"
case STRING:
return "string"
case NUMBER:
return "number"
case DURATION:
return "duration"
}
return fmt.Sprintf("%q", i)
}
const eof = -1
// stateFn represents the state of the scanner as a function that returns the next state.
type stateFn func(*Lexer) stateFn
// Pos is the position in a string.
// Negative numbers indicate undefined positions.
type Pos int
// Lexer holds the state of the scanner.
type Lexer struct {
input string // The string being scanned.
state stateFn // The next lexing function to enter.
pos Pos // Current position in the input.
start Pos // Start position of this Item.
width Pos // Width of last rune read from input.
lastPos Pos // Position of most recent Item returned by NextItem.
itemp *Item // Pointer to where the next scanned item should be placed.
scannedItem bool // Set to true every time an item is scanned.
parenDepth int // Nesting depth of ( ) exprs.
braceOpen bool // Whether a { is opened.
bracketOpen bool // Whether a [ is opened.
gotColon bool // Whether we got a ':' after [ was opened.
stringOpen rune // Quote rune of the string currently being read.
// seriesDesc is set when a series description for the testing
// language is lexed.
seriesDesc bool
}
// next returns the next rune in the input.
func (l *Lexer) next() rune {
if int(l.pos) >= len(l.input) {
l.width = 0
return eof
}
r, w := utf8.DecodeRuneInString(l.input[l.pos:])
l.width = Pos(w)
l.pos += l.width
return r
}
// peek returns but does not consume the next rune in the input.
func (l *Lexer) peek() rune {
r := l.next()
l.backup()
return r
}
// backup steps back one rune. Can only be called once per call of next.
func (l *Lexer) backup() {
l.pos -= l.width
}
// emit passes an Item back to the client.
func (l *Lexer) emit(t ItemType) {
*l.itemp = Item{t, l.start, l.input[l.start:l.pos]}
l.start = l.pos
l.scannedItem = true
}
// ignore skips over the pending input before this point.
func (l *Lexer) ignore() {
l.start = l.pos
}
// accept consumes the next rune if it's from the valid set.
func (l *Lexer) accept(valid string) bool {
if strings.ContainsRune(valid, l.next()) {
return true
}
l.backup()
return false
}
// acceptRun consumes a run of runes from the valid set.
func (l *Lexer) acceptRun(valid string) {
for strings.ContainsRune(valid, l.next()) {
// consume
}
l.backup()
}
// errorf returns an error token and terminates the scan by passing
// back a nil pointer that will be the next state, terminating l.NextItem.
func (l *Lexer) errorf(format string, args ...interface{}) stateFn {
*l.itemp = Item{ERROR, l.start, fmt.Sprintf(format, args...)}
l.scannedItem = true
return nil
}
// NextItem writes the next item to the provided address.
func (l *Lexer) NextItem(itemp *Item) {
l.scannedItem = false
l.itemp = itemp
if l.state != nil {
for !l.scannedItem {
l.state = l.state(l)
}
} else {
l.emit(EOF)
}
l.lastPos = l.itemp.Pos
}
// Lex creates a new scanner for the input string.
func Lex(input string) *Lexer {
l := &Lexer{
input: input,
state: lexStatements,
}
return l
}
// lineComment is the character that starts a line comment.
const lineComment = "#"
// lexStatements is the top-level state for lexing.
func lexStatements(l *Lexer) stateFn {
if l.braceOpen {
return lexInsideBraces
}
if strings.HasPrefix(l.input[l.pos:], lineComment) {
return lexLineComment
}
switch r := l.next(); {
case r == eof:
if l.parenDepth != 0 {
return l.errorf("unclosed left parenthesis")
} else if l.bracketOpen {
return l.errorf("unclosed left bracket")
}
l.emit(EOF)
return nil
case r == ',':
l.emit(COMMA)
case isSpace(r):
return lexSpace
case r == '*':
l.emit(MUL)
case r == '/':
l.emit(DIV)
case r == '%':
l.emit(MOD)
case r == '+':
l.emit(ADD)
case r == '-':
l.emit(SUB)
case r == '^':
l.emit(POW)
case r == '=':
if t := l.peek(); t == '=' {
l.next()
l.emit(EQL)
} else if t == '~' {
return l.errorf("unexpected character after '=': %q", t)
} else {
l.emit(ASSIGN)
}
case r == '!':
if t := l.next(); t == '=' {
l.emit(NEQ)
} else {
return l.errorf("unexpected character after '!': %q", t)
}
case r == '<':
if t := l.peek(); t == '=' {
l.next()
l.emit(LTE)
} else {
l.emit(LSS)
}
case r == '>':
if t := l.peek(); t == '=' {
l.next()
l.emit(GTE)
} else {
l.emit(GTR)
}
case isDigit(r) || (r == '.' && isDigit(l.peek())):
l.backup()
return lexNumberOrDuration
case r == '"' || r == '\'':
l.stringOpen = r
return lexString
case r == '`':
l.stringOpen = r
return lexRawString
case isAlpha(r) || r == ':':
if !l.bracketOpen {
l.backup()
return lexKeywordOrIdentifier
}
if l.gotColon {
return l.errorf("unexpected colon %q", r)
}
l.emit(COLON)
l.gotColon = true
case r == '(':
l.emit(LEFT_PAREN)
l.parenDepth++
return lexStatements
case r == ')':
l.emit(RIGHT_PAREN)
l.parenDepth--
if l.parenDepth < 0 {
return l.errorf("unexpected right parenthesis %q", r)
}
return lexStatements
case r == '{':
l.emit(LEFT_BRACE)
l.braceOpen = true
return lexInsideBraces
case r == '[':
if l.bracketOpen {
return l.errorf("unexpected left bracket %q", r)
}
l.gotColon = false
l.emit(LEFT_BRACKET)
if isSpace(l.peek()) {
skipSpaces(l)
}
l.bracketOpen = true
return lexDuration
case r == ']':
if !l.bracketOpen {
return l.errorf("unexpected right bracket %q", r)
}
l.emit(RIGHT_BRACKET)
l.bracketOpen = false
default:
return l.errorf("unexpected character: %q", r)
}
return lexStatements
}
// lexInsideBraces scans the inside of a vector selector. Keywords are ignored and
// scanned as identifiers.
func lexInsideBraces(l *Lexer) stateFn {
if strings.HasPrefix(l.input[l.pos:], lineComment) {
return lexLineComment
}
switch r := l.next(); {
case r == eof:
return l.errorf("unexpected end of input inside braces")
case isSpace(r):
return lexSpace
case isAlpha(r):
l.backup()
return lexIdentifier
case r == ',':
l.emit(COMMA)
case r == '"' || r == '\'':
l.stringOpen = r
return lexString
case r == '`':
l.stringOpen = r
return lexRawString
case r == '=':
if l.next() == '~' {
l.emit(EQL_REGEX)
break
}
l.backup()
l.emit(EQL)
case r == '!':
switch nr := l.next(); {
case nr == '~':
l.emit(NEQ_REGEX)
case nr == '=':
l.emit(NEQ)
default:
return l.errorf("unexpected character after '!' inside braces: %q", nr)
}
case r == '{':
return l.errorf("unexpected left brace %q", r)
case r == '}':
l.emit(RIGHT_BRACE)
l.braceOpen = false
if l.seriesDesc {
return lexValueSequence
}
return lexStatements
default:
return l.errorf("unexpected character inside braces: %q", r)
}
return lexInsideBraces
}
// lexValueSequence scans a value sequence of a series description.
func lexValueSequence(l *Lexer) stateFn {
switch r := l.next(); {
case r == eof:
return lexStatements
case isSpace(r):
l.emit(SPACE)
lexSpace(l)
case r == '+':
l.emit(ADD)
case r == '-':
l.emit(SUB)
case r == 'x':
l.emit(TIMES)
case r == '_':
l.emit(BLANK)
case isDigit(r) || (r == '.' && isDigit(l.peek())):
l.backup()
lexNumber(l)
case isAlpha(r):
l.backup()
// We might lex invalid Items here but this will be caught by the parser.
return lexKeywordOrIdentifier
default:
return l.errorf("unexpected character in series sequence: %q", r)
}
return lexValueSequence
}
// lexEscape scans a string escape sequence. The initial escaping character (\)
// has already been seen.
//
// NOTE: This function as well as the helper function digitVal() and associated
// tests have been adapted from the corresponding functions in the "go/scanner"
// package of the Go standard library to work for Prometheus-style strings.
// None of the actual escaping/quoting logic was changed in this function - it
// was only modified to integrate with our lexer.
func lexEscape(l *Lexer) stateFn {
var n int
var base, max uint32
ch := l.next()
switch ch {
case 'a', 'b', 'f', 'n', 'r', 't', 'v', '\\', l.stringOpen:
return lexString
case '0', '1', '2', '3', '4', '5', '6', '7':
n, base, max = 3, 8, 255
case 'x':
ch = l.next()
n, base, max = 2, 16, 255
case 'u':
ch = l.next()
n, base, max = 4, 16, unicode.MaxRune
case 'U':
ch = l.next()
n, base, max = 8, 16, unicode.MaxRune
case eof:
l.errorf("escape sequence not terminated")
return lexString
default:
l.errorf("unknown escape sequence %#U", ch)
return lexString
}
var x uint32
for n > 0 {
d := uint32(digitVal(ch))
if d >= base {
if ch == eof {
l.errorf("escape sequence not terminated")
return lexString
}
l.errorf("illegal character %#U in escape sequence", ch)
return lexString
}
x = x*base + d
ch = l.next()
n--
}
if x > max || 0xD800 <= x && x < 0xE000 {
l.errorf("escape sequence is an invalid Unicode code point")
}
return lexString
}
// digitVal returns the digit value of a rune or 16 in case the rune does not
// represent a valid digit.
func digitVal(ch rune) int {
switch {
case '0' <= ch && ch <= '9':
return int(ch - '0')
case 'a' <= ch && ch <= 'f':
return int(ch - 'a' + 10)
case 'A' <= ch && ch <= 'F':
return int(ch - 'A' + 10)
}
return 16 // Larger than any legal digit val.
}
// skipSpaces skips the spaces until a non-space is encountered.
func skipSpaces(l *Lexer) {
for isSpace(l.peek()) {
l.next()
}
l.ignore()
}
// lexString scans a quoted string. The initial quote has already been seen.
func lexString(l *Lexer) stateFn {
Loop:
for {
switch l.next() {
case '\\':
return lexEscape
case utf8.RuneError:
l.errorf("invalid UTF-8 rune")
return lexString
case eof, '\n':
return l.errorf("unterminated quoted string")
case l.stringOpen:
break Loop
}
}
l.emit(STRING)
return lexStatements
}
// lexRawString scans a raw quoted string. The initial quote has already been seen.
func lexRawString(l *Lexer) stateFn {
Loop:
for {
switch l.next() {
case utf8.RuneError:
l.errorf("invalid UTF-8 rune")
return lexRawString
case eof:
l.errorf("unterminated raw string")
return lexRawString
case l.stringOpen:
break Loop
}
}
l.emit(STRING)
return lexStatements
}
// lexSpace scans a run of space characters. One space has already been seen.
func lexSpace(l *Lexer) stateFn {
for isSpace(l.peek()) {
l.next()
}
l.ignore()
return lexStatements
}
// lexLineComment scans a line comment. Left comment marker is known to be present.
func lexLineComment(l *Lexer) stateFn {
l.pos += Pos(len(lineComment))
for r := l.next(); !isEndOfLine(r) && r != eof; {
r = l.next()
}
l.backup()
l.emit(COMMENT)
return lexStatements
}
func lexDuration(l *Lexer) stateFn {
if l.scanNumber() {
return l.errorf("missing unit character in duration")
}
// Next two chars must be a valid unit and a non-alphanumeric.
if l.accept("smhdwy") {
if isAlphaNumeric(l.next()) {
return l.errorf("bad duration syntax: %q", l.input[l.start:l.pos])
}
l.backup()
l.emit(DURATION)
return lexStatements
}
return l.errorf("bad duration syntax: %q", l.input[l.start:l.pos])
}
// lexNumber scans a number: decimal, hex, oct or float.
func lexNumber(l *Lexer) stateFn {
if !l.scanNumber() {
return l.errorf("bad number syntax: %q", l.input[l.start:l.pos])
}
l.emit(NUMBER)
return lexStatements
}
// lexNumberOrDuration scans a number or a duration Item.
func lexNumberOrDuration(l *Lexer) stateFn {
if l.scanNumber() {
l.emit(NUMBER)
return lexStatements
}
// Next two chars must be a valid unit and a non-alphanumeric.
if l.accept("smhdwy") {
if isAlphaNumeric(l.next()) {
return l.errorf("bad number or duration syntax: %q", l.input[l.start:l.pos])
}
l.backup()
l.emit(DURATION)
return lexStatements
}
return l.errorf("bad number or duration syntax: %q", l.input[l.start:l.pos])
}
// scanNumber scans numbers of different formats. The scanned Item is
// not necessarily a valid number. This case is caught by the parser.
func (l *Lexer) scanNumber() bool {
digits := "0123456789"
// Disallow hexadecimal in series descriptions as the syntax is ambiguous.
if !l.seriesDesc && l.accept("0") && l.accept("xX") {
digits = "0123456789abcdefABCDEF"
}
l.acceptRun(digits)
if l.accept(".") {
l.acceptRun(digits)
}
if l.accept("eE") {
l.accept("+-")
l.acceptRun("0123456789")
}
// Next thing must not be alphanumeric unless it's the times token
// for series repetitions.
if r := l.peek(); (l.seriesDesc && r == 'x') || !isAlphaNumeric(r) {
return true
}
return false
}
// lexIdentifier scans an alphanumeric identifier. The next character
// is known to be a letter.
func lexIdentifier(l *Lexer) stateFn {
for isAlphaNumeric(l.next()) {
// absorb
}
l.backup()
l.emit(IDENTIFIER)
return lexStatements
}
// lexKeywordOrIdentifier scans an alphanumeric identifier which may contain
// a colon rune. If the identifier is a keyword the respective keyword Item
// is scanned.
func lexKeywordOrIdentifier(l *Lexer) stateFn {
Loop:
for {
switch r := l.next(); {
case isAlphaNumeric(r) || r == ':':
// absorb.
default:
l.backup()
word := l.input[l.start:l.pos]
if kw, ok := key[strings.ToLower(word)]; ok {
l.emit(kw)
} else if !strings.Contains(word, ":") {
l.emit(IDENTIFIER)
} else {
l.emit(METRIC_IDENTIFIER)
}
break Loop
}
}
if l.seriesDesc && l.peek() != '{' {
return lexValueSequence
}
return lexStatements
}
func isSpace(r rune) bool {
return r == ' ' || r == '\t' || r == '\n' || r == '\r'
}
// isEndOfLine reports whether r is an end-of-line character.
func isEndOfLine(r rune) bool {
return r == '\r' || r == '\n'
}
// isAlphaNumeric reports whether r is an alphabetic, digit, or underscore.
func isAlphaNumeric(r rune) bool {
return isAlpha(r) || isDigit(r)
}
// isDigit reports whether r is a digit. Note: we cannot use unicode.IsDigit()
// instead because that also classifies non-Latin digits as digits. See
// https://github.com/prometheus/prometheus/issues/939.
func isDigit(r rune) bool {
return '0' <= r && r <= '9'
}
// isAlpha reports whether r is an alphabetic or underscore.
func isAlpha(r rune) bool {
return r == '_' || ('a' <= r && r <= 'z') || ('A' <= r && r <= 'Z')
}
// isLabel reports whether the string can be used as label.
func isLabel(s string) bool {
if len(s) == 0 || !isAlpha(rune(s[0])) {
return false
}
for _, c := range s[1:] {
if !isAlphaNumeric(c) {
return false
}
}
return true
}