Nicer error
| author |
Steve Losh <steve@stevelosh.com> |
| date |
Thu, 25 Aug 2022 23:10:20 -0400 |
| parents |
37efd8463e96 |
| children |
(none) |
(in-package :jarl)
;;;; Input --------------------------------------------------------------------
(defparameter *read-size-limit* (expt 2 30)
"The maximum number of characters to read in a single `jarl:read` call.
If more than this number of characters would have to be read to finish reading
a single object, a `json-size-limit-exceeded-error` will be signaled.
If both the size and depth limits are exceeded by exactly the same character,
it is unspecified which of the two errors will be signaled.")
(defparameter *read-depth-limit* 100
"The maximum depth of nested objects and vectors to allow in a single `jarl:read` call.
If reading a single object would require descending into more than this number
of JSON objects and/or arrays, a `json-depth-limit-exceeded-error` error will
be signaled.
If both the size and depth limits are exceeded by exactly the same character,
it is unspecified which of the two errors will be signaled.")
(defparameter *indent* nil)
(defstruct (input (:constructor make-input%))
(stream nil :type stream)
(line 1 :type (and fixnum (integer 0)))
(column 0 :type (and fixnum (integer 0)))
(depth 0 :type (and fixnum (integer 0)))
(depth-limit *read-depth-limit* :type (and fixnum (integer 0)))
(size 0 :type (and fixnum (integer 0)))
(size-limit *read-size-limit* :type (and fixnum (integer 0)))
(string-buffer nil :type (or null stream)))
(defun ensure-stream (stream-or-string)
(etypecase stream-or-string
(stream stream-or-string)
(string (make-string-input-stream stream-or-string))))
(defun make-input (stream-or-string)
(make-input% :stream (ensure-stream stream-or-string)))
(defun reset-limits (input)
(setf (input-depth input) 0
(input-size input) 0
(input-depth-limit input) *read-depth-limit*
(input-size-limit input) *read-size-limit*))
(defun reset-position (input)
(setf (input-line input) 0
(input-column input) 0))
(defun p (input &optional (eof :eof)) ; peek
(declare (type input input)
(optimize (speed 3) (safety 1) (debug 1)))
(peek-char nil (input-stream input) nil eof))
(defun r (input) ; read
(declare (type input input)
(optimize (speed 3) (safety 1) (debug 1)))
(let ((character (read-char (input-stream input) nil :eof)))
(case character
(#\newline (progn
(incf (input-line input))
(setf (input-column input) 0)))
(#\tab (incf (input-column input) 8))
(t (incf (input-column input))))
(when (> (incf (input-size input))
(input-size-limit input))
(error 'json-size-limit-exceeded-error
:line (input-line input)
:column (input-column input)
:limit (input-size-limit input)))
character))
;;;; Errors -------------------------------------------------------------------
(define-condition json-error (error)
((line :accessor line :initarg :line)
(column :accessor column :initarg :column)))
(define-condition json-reading-error (json-error)
((class-designator :accessor class-designator :initarg :class-designator)
(message :accessor message :initarg :message))
(:report
(lambda (c stream)
(format stream "Error reading JSON~@[ into ~S~] at line ~D column ~D: ~A"
(class-designator c)
(line c)
(column c)
(message c)))))
(define-condition malformed-json-error (json-reading-error)
())
(define-condition unknown-json-slot-error (json-reading-error)
((name :accessor name :initarg :name)))
(define-condition json-limit-exceeded-error (json-reading-error)
((limit :accessor limit :initarg :limit)
(limit-name :allocation :class))
(:report
(lambda (c stream)
(format stream "~:(~A~) limit (~D) exceeded while reading JSON at line ~D column ~D."
(slot-value c 'limit-name)
(limit c)
(line c)
(column c)))))
(define-condition json-size-limit-exceeded-error (json-limit-exceeded-error)
((limit-name :initform "size")))
(define-condition json-depth-limit-exceeded-error (json-limit-exceeded-error)
((limit-name :initform "depth")))
(defun e (class input format-string &rest args) ; error
(error 'malformed-json-error
:class-designator class
:line (input-line input)
:column (input-column input)
:message (apply #'format nil format-string args)))
(defun incf-depth (input)
(declare (type input input)
(optimize (speed 3) (safety 1) (debug 1)))
(when (> (incf (input-depth input))
(input-depth-limit input))
(error 'json-depth-limit-exceeded-error
:line (input-line input)
:column (input-column input)
:limit (input-depth-limit input))))
(defun decf-depth (input)
(declare (type input input)
(optimize (speed 3) (safety 1) (debug 1)))
(decf (input-depth input)))
;;;; Parsing Utilities --------------------------------------------------------
(defun skip-whitespace (input)
(loop :for ch = (p input)
:while (member ch '(#\space #\tab #\newline #\linefeed #\return))
:do (r input)))
(defun requires-escape-p (character)
(or (char= #\" character)
(char= #\\ character)
(<= (char-code character) #x1F))) ; TODO: Technically this isn't portable.
(defun parse-literal (input literal remaining-characters)
(loop :for next :across remaining-characters
:for char = (r input)
:unless (eql next char)
:do (e 'keyword input "expected ~S when reading ~S but got ~S" next literal char))
literal)
(defun parse-hex-digit (input)
(let ((ch (r input)))
(if (eql :eof ch)
(e nil input "cannot parse \\u escape sequence, got ~S" :eof)
(or (digit-char-p ch 16)
(e nil input "cannot parse \\u escape sequence, ~S is not a hexadecimal digit" ch)))))
(defun parse-escaped-character (input)
(let ((ch (r input)))
(case ch
(#\" #\")
(#\\ #\\)
(#\/ #\/)
(#\b #\backspace)
(#\f (code-char #x0C))
(#\n #\linefeed)
(#\r #\return)
(#\t #\tab)
(#\u (let ((a (parse-hex-digit input)) ; todo handle surrogate pairs
(b (parse-hex-digit input))
(c (parse-hex-digit input))
(d (parse-hex-digit input)))
(code-char (+ (* a (expt 16 3)) ; todo maybe do this more portably
(* b (expt 16 2))
(* c (expt 16 1))
(* d (expt 16 0))))))
(t (e nil input "bad escape sequence ~S ~S" #\\ ch)))))
(defun parse-int (input &optional (allow-leading-zero t))
(loop :with i = 0
:with n = 0
:for ch = (p input #\e)
:for digit = (digit-char-p ch)
:while digit
:do (progn (r input)
(when (and (not allow-leading-zero)
(zerop n) ; leading
(zerop digit) ; zero
(digit-char-p (p input #\e))) ; but not a bare zero
(e nil input "bad leading zero"))
(incf n)
(setf i (+ (* 10 i) digit)))
:finally (if (zerop n)
(e nil input "expected an integer")
(return (values i n)))))
(defun parse-exponent (input)
(let* ((char (p input))
(sign (if (member char '(#\+ #\-))
(progn (r input)
(case char
(#\+ 1)
(#\- -1)))
1)))
(* sign (parse-int input))))
(defun parse-number (input)
(let ((sign 1) integer
(fractional 0) (fractional-length 0)
(exponent 0) has-exponent)
(when (eql #\- (p input))
(r input)
(setf sign -1))
(setf integer (parse-int input nil))
(when (eql #\. (p input))
(r input)
(setf (values fractional fractional-length) (parse-int input)))
(when (member (p input) '(#\e #\E))
(r input)
(setf exponent (parse-exponent input)
has-exponent t))
(if (and (zerop fractional-length) (not has-exponent))
(* sign integer)
(values
(coerce ;; todo make this less horrifying
(read-from-string (format nil "~A~D.~V,'0Dd~D"
(if (= -1 sign) #\- #\+)
integer
fractional-length
fractional
exponent))
'double-float)))))
(defun parse-kv-separator (class input)
(skip-whitespace input)
(let ((ch (r input)))
(unless (eql #\: ch)
(e class input "expected separator ~S but got ~S" #\: ch))
(skip-whitespace input)))
;;;; Readers ------------------------------------------------------------------
(defgeneric read% (class contained-class input))
(defmethod read% ((class (eql 'keyword)) contained-class input)
(declare (ignore contained-class))
(let ((ch (r input)))
(case ch
(#\t (parse-literal input :true "rue"))
(#\f (parse-literal input :false "alse"))
(t (e 'keyword input "expected ~S or ~S but got ~S" #\t #\f ch)))))
(defmethod read% ((class (eql 'null)) contained-class input)
(declare (ignore contained-class))
(let ((ch (r input)))
(if (eql ch #\n)
(parse-literal input nil "ull")
(e 'null input "expected ~S but got ~S" #\n ch))))
(defmethod read% ((class (eql 'vector)) contained-class input)
(let ((ch (r input)))
(unless (eql ch #\[)
(e 'vector input "expected ~S but got ~S" #\[ ch)))
(incf-depth input)
(skip-whitespace input)
;; todo allow specialized vectors?
(if (eql (p input) #\])
(progn (r input)
(decf-depth input)
(vector))
(coerce
(loop
:with c = (car contained-class)
:with cc = (cadr contained-class)
:collect (read% c cc input)
:do (progn
(skip-whitespace input)
(let ((ch (r input)))
(case ch
(#\] (decf-depth input) (loop-finish))
(#\, (skip-whitespace input))
(t (e 'vector input "expected ~S or ~S but got ~S." #\] #\, ch))))))
'vector)))
(defmethod read% ((class (eql 'string)) contained-class input)
(declare (ignore contained-class))
(let ((ch (r input)))
(unless (eql ch #\")
(e 'string input "expected opening ~S but got ~S" #\" ch)))
(loop :with s = (or (input-string-buffer input)
(setf (input-string-buffer input)
(make-string-output-stream)))
:for ch = (r input)
:do (case ch
(:eof (e 'string input "got ~S" :eof))
(#\\ (write-char (parse-escaped-character input) s))
(#\" (return (get-output-stream-string s)))
(t (if (requires-escape-p ch)
(e 'string input "bad unescaped character ~S" ch)
(write-char ch s))))))
(defmethod read% ((class (eql 'hash-table)) contained-class input)
(let ((ch (r input)))
(unless (eql ch #\{)
(e 'hash-table input "expected ~S but got ~S" #\{ ch)))
(incf-depth input)
(skip-whitespace input)
(let ((result (make-hash-table :test #'equal)))
(if (eql (p input) #\})
(progn (r input)
(decf-depth input))
(loop
:with c = (car contained-class)
:with cc = (cadr contained-class)
:for name = (read% 'string nil input)
:for value = (progn (parse-kv-separator 'hash-table input)
(skip-whitespace input)
(read% c cc input))
:do (progn
(setf (gethash name result) value)
(skip-whitespace input)
(let ((ch (r input)))
(case ch
(#\} (decf-depth input) (loop-finish))
(#\, (skip-whitespace input))
(t (e 'hash-table input "expected ~S or ~S but got ~S" #\} #\, ch)))))))
result))
(defmethod read% ((class (eql 'number)) contained-class input)
(declare (ignore contained-class))
(let ((ch (p input)))
(unless (member ch '(#\- #\0 #\1 #\2 #\3 #\4 #\5 #\6 #\7 #\8 #\9))
(r input) ; chomp to ensure accurate column count
(e 'number input "expected digit or ~S but got ~S" #\- ch)))
(parse-number input))
(defmethod read% ((class (eql 'nullable)) contained-class input)
(case (p input)
(:eof (e `(or null ,input) input "got ~S" :eof))
(#\n (read% 'null nil input))
(t (read% (first contained-class) (second contained-class) input))))
(defmethod read% ((class (eql t)) contained-class input)
(declare (ignore contained-class))
(skip-whitespace input)
(case (p input)
(:eof (r input) (e 't input "got ~S" :eof))
((#\t #\f) (read% 'keyword nil input))
(#\n (read% 'null nil input))
(#\" (read% 'string nil input))
(#\{ (read% 'hash-table '(t) input))
(#\[ (read% 'vector '(t) input))
((#\- #\0 #\1 #\2 #\3 #\4 #\5 #\6 #\7 #\8 #\9) (read% 'number nil input))
(t (e 't input "unexpected character ~S" (r input)))))
;;;; Printing -----------------------------------------------------------------
(defun write-escaped-char (char stream)
(case char
((#\newline #\linefeed) (write-string "\\n" stream))
(#\return (write-string "\\r" stream))
(#\\ (write-string "\\\\" stream))
(t (format stream "\\u~4,'0X" (char-code char)))))
(declaim (inline indent))
(defun indent (i stream)
(when i
(format stream "~%~v@T" i)))
(defgeneric print% (thing stream indent))
(defmethod print% ((thing null) stream indent)
(declare (ignore indent))
(write-string "null" stream))
(defmethod print% ((thing string) stream indent)
(declare (ignore indent))
(write-char #\" stream)
(loop :for char :across thing
:do (if (requires-escape-p char)
(write-escaped-char char stream)
(write-char char stream)))
(write-char #\" stream))
(defmethod print% ((thing vector) stream indent &aux (first t))
(write-char #\[ stream)
(when indent (incf indent 2))
(loop :for object :across thing
:do (progn (if first
(setf first nil)
(write-char #\, stream))
(indent indent stream)
(print% object stream indent)))
(when (and indent (not first))
(indent (- indent 2) stream))
(write-char #\] stream))
(defmethod print% ((thing hash-table) stream indent &aux (first t))
(write-char #\{ stream)
(when indent (incf indent 2))
(maphash (lambda (name value)
(if first
(setf first nil)
(write-char #\, stream))
(indent indent stream)
(assert (stringp name))
(print% name stream indent)
(write-char #\: stream)
(when indent (write-char #\space stream))
(print% value stream indent))
thing)
(when (and indent (not first))
(indent (- indent 2) stream))
(write-char #\} stream))
(defmethod print% ((thing single-float) stream indent)
(declare (ignore indent))
(let ((*read-default-float-format* 'single-float))
(princ thing stream)))
(defmethod print% ((thing double-float) stream indent)
(declare (ignore indent))
(let ((*read-default-float-format* 'double-float))
(princ thing stream)))
(defmethod print% ((thing integer) stream indent)
(declare (ignore indent))
(format stream "~D" thing))
(defmethod print% ((thing (eql :false)) stream indent)
(declare (ignore indent))
(write-string "false" stream))
(defmethod print% ((thing (eql :true)) stream indent)
(declare (ignore indent))
(write-string "true" stream))
;;;; API ----------------------------------------------------------------------
(defun canonicalize-class-designator (class-designator)
(flet ((fail () (error "Malformed class designator ~S" class-designator)))
(etypecase class-designator
(cons (destructuring-bind (head a &optional (b nil b?)) class-designator
(ecase head
; e.g. (vector foo)
((hash-table vector)
(progn (when b? (fail))
(list head (canonicalize-class-designator a))))
; e.g. (or null foo)
(or (progn (unless b? (fail)) ; must have a second option
(when (eql 'null b) (rotatef a b)) ; sort a/b
(unless (eql 'null a) (fail)) ; no arbitrary ors
(list 'nullable (canonicalize-class-designator b)))))))
(symbol (case class-designator
(vector '(vector (t)))
(hash-table '(hash-table (t)))
(t (list class-designator)))))))
(defun read (class-designator input &optional (eof-error-p t) eof)
(etypecase input
(input (reset-limits input))
((or stream string) (setf input (make-input input))))
(skip-whitespace input)
(if (eql :eof (p input))
(if eof-error-p
(error 'end-of-file)
eof)
(destructuring-bind (class &optional contained)
(canonicalize-class-designator class-designator)
(read% class contained input))))
(defun print (object &optional (stream *standard-output*))
(let ((*read-default-float-format* 'double-float)
(*print-base* 10)
(indent (if *indent* 0 nil)))
(etypecase stream
(stream (print% object stream indent) (values))
((eql t) (print% object *standard-output* indent) (values))
(null (with-output-to-string (s) (print% object s indent))))))