Before this commit, continuation lines of multi-line values in variable
declaration initializers were aligned with the variable name:
let foo = {
a: 5,
b: 6
};
This was highly irregular, maintenance intensive, and made declarations
look different from assignments.
This commit changes the indentation to be more regular and similar to
assignments:
let foo = {
a: 5,
b: 6
};
Move "use strict" directives to the first line of each file. In
particular, move them above any ESLint comments, which are far less
important.
There are few exceptions:
Executable files
In these, the "use strict" directive must give way to the shebang.
lib/parser.js
Here, the "Generated by..." comment comes first. Also, ESLint
comments are prepended in post-processing.
Use one var/let/const per variable, but only for initialized variables.
Uninitialized variables are still grouped into one var/let/const
declaration as I don't see any value in separating them. This approach
reflects the fact that initialized and uninitialized var/let/const
declarations are really two different things.
See #443.
The for-in statement in JavaScript iterates also over inherited
properties. This is typically not desired and requires adding a
check using Object.prototype.hasOwnProperty inside the loop.
This commit replaces all for-in statements and related checks inside
them with iteration over Object.keys(...). The iteration is performed
using either Array.prototype.forEach of a plain for loop.
Because arrow functions work rather differently than normal functions (a
bad design mistake if you ask me), I decided to be conservative with the
conversion.
I converted:
* event handlers
* callbacks
* arguments to Array.prototype.map & co.
* small standalone lambda functions
I didn't convert:
* functions assigned to object literal properties (the new shorthand
syntax would be better here)
* functions passed to "describe", "it", etc. in specs (because Jasmine
relies on dynamic "this")
See #442.
This is purely a mechanical change, not taking advantage of block scope
of "let" and "const". Minimizing variable scope will come in the next
commit.
In general, "var" is converted into "let" and "const" is used only for
immutable variables of permanent character (generally spelled in
ALL_CAPS). Using it for any immutable variable regardless on its
permanence would feel confusing.
Any code which is not transpiled and needs to run in ES6 environment
(examples, code in grammars embedded in specs, ...) is kept unchanged.
This is also true for code generated by PEG.js.
See #442.
This will allow to use ES2015 constructs in spec code.
The change required introducing a small server, which serves both PEG.js
and spec code passed through Babel and bundled together. This allowed to
convert the specs to regular modules and get rid of the hackery that was
previously needed to make them run both in Node.js and in the browser.
Note the specs no longer exercise the browser version. This will allow
to spec PEG.js internals in the future.
See #442.
Rename compiler passes as follows:
reportLeftRecursion -> reportInfiniteRecursion
reportInfiniteLoops -> reportInfiniteRepetition
This reflects the fact that both passes detect different ways of causing
the same problem (possible infinite loop when parsing).
The new terminology is more precise and in line with commonly used
programming languages.
The change involves mainly renaming related compiler pass and files
associated with it.
The "parser" variable allowed access to the parser object. Among other
things, this made it possible to invoke the parser recursively using
"parser.parse".
One problem with the "parser" variable is that it bakes in the idea that
the parser is an *object*, not a *module*. While this is true now, it
won't necessarily be in the future, when parsers may be exported as ES6
modules. Also, people tend to use parsers as modules even today, e.g.
like this:
var parse = require("parser").parse;
var result = parse(...);
Such usage broke the "parser" variable (as it was implemented).
For this reasons I decided to remove the "parser" variable. If someone
needs to do tricks like recursive invocation of the parser, he/she must
pass the parser or the "parse" function itself using options.
Related to #433.
Until now, expectations were constructed using object literals. This
commit changes the construction to use factory functions.
This change makes generated parsers slightly smaller because property
names don't have to be repeated many times and factory function calls
are more amenable to minifying.
Some numbers based on the aggregate size of parsers generated from
examples/*.pegjs:
Optimization Minified? Size before Size after Saving
------------------------------------------------------------
speed no 719066 716063 0.42%
speed yes 188998 180202 4.65%
size no 194810 197813 1.52%
size yes 108782 99947 8.12%
(Minification was done using "uglify --mangle --compress" with
uglify-js 2.4.24.)
Instead of pre-generating expectation descriptions when generating
parsers, generate them dynamically from structured information contained
in the expectations.
This change makes descriptions a presentation-only concept. It also
makes generated parsers smaller.
Before this commit, expectations were sorted and de-duplicated before
they were passed to "buildMessage" and exposed in the "expected"
property of syntax errors. This commit moves this processing into
"buildMessage" and rewrites it to process only expectation descriptions.
This means expectations exposed in the "expected" property are "raw"
(not sorted and de-duplicated).
This change will allow us to get rid of the "description" property of
expectations and compute descriptions dynamically from structured
information in the expectations. This will make descriptions a
presentation-only concept. It will also make generated parsers smaller.
Note that to keep expectations in the "expected" property sorted even
without the "description" property, some sorting scheme based on
structured information in the expectations would have to be devised,
which would complicate things with only a little benefit. Therefore I
chose to keep the expectations there "raw".
Changes:
* Remove the "value" property (it is replaced by other properties).
* Add the "parts", "inverted", and "ignoreCase" properties (which
allow more structured access to expectation data).
David Majda
Mingun