The "global-require" rule is disabled in ESLint configuration used by
PEG.js, but the idea is not bad, so let's make all static "require"
calls global.
Follow-up to #407.
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
};
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 change makes it possible to use "generate" as a module function,
e.g. like this:
var generate = require("pegjs").generate;
var parser = generate(...);
Fixes#433.
In most places, we talk about "generating a parser", not "building a
parser", which the function name should reflect. Also, mentioning a
parser in the name is not necessary as in case of a parser generator
it's pretty clear what is generated.
So far, PEG.js was exported in a "PEG" global variable when no module
loader was detected. The same variable name was also conventionally used
when requiring it in Node.js or otherwise referring to it. This was
reflected in various places in the code, documentation, examples, etc.
This commit changes the variable name to "peg" and fixes all relevant
occurrences. The main reason for the change is that in Node.js, modules
are generally referred to by lower-case variable names, so "PEG" was
sticking out when used in Node.js projects.
Instead of testing arguments.length to see whether an optional parameter
was passed to a function, compare its value to "undefined". This
approach has two advantages:
* It is in line with handling of default parameters in ES6.
* Optional parameters are actually spelled out in the parameter
list.
There is also one important disadvantage, namely that it's impossible to
pass "undefined" as an optional parameter value. This required a small
change in two tests.
Additional notes:
* Default parameter values are set in assignments immediately
after the function header. This reflects the fact that these
assignments really belong to the parameter list (which is where they
are in ES6).
* Parameter values are checked against "void 0" in places where
"undefined" can potentially be redefiend.
Split lib/utils.js into multiple files. Some of the functions were
generic, these were moved into files in lib/utils. Other funtions were
specific for the compiler, these were moved to files in lib/compiler.
This commit only moves functions around -- there is no renaming and
cleanup performed. Both will come later.
Modules now generally store the exported object in a named variable or
function first and only assign |module.exports| at the very end. This is
a difference when compared to style used until now, where most modules
started with a |module.exports| assignment.
I think the explicit name helps readability and understandability.
Also added few missing |hasOwnProperty| calls that JSHint didn't detect
because it only looks whether there is an |if| statement wrapping the
loop body.
The compiler passes are now split into three stages:
* check -- passes that check for various error conditions
* transform -- passes that transform the AST (e.g. to perform
optimizations)
* generate -- passes that are related to code generation
Splitting the passes into stages is important for plugins. For example,
if a plugin wants to add a new optimization pass, it can add it at the
end of the "transform" stage without any knowledge about other passes it
contains. Similarly, if it wants to generate something else than the
default code generator does from the AST, it can just replace all passes
in the "generate" stage by its own one(s).
More generally, the stages make it possible to write plugins that do not
depend on names and actions of specific passes (which I consider
internal and subject of change), just on the definition of stages (which
I consider a public API with to which semver rules apply).
Implements part of GH-106.
The |plugins| option allows users to use plugins that change how PEG.js
operates.
A plugin is any JavaScript object with a |use| method. After the user
calls |PEG.buildParser|, this method is called for each plugin with the
following two parameters:
* PEG.js config that describes used grammar parser and compiler
passes used to generate the parser
* options passed by user to |PEG.buildParser|
The plugin is expected to change the config as needed, possibly based on
the options passed by user. It can e.g. change the used grammar parser,
change the compiler passes (including adding its own), etc. This way it
can extend PEG.js in a flexible way.
Implements part of GH-106.
The |passes| parameter will allow to pass the list of passes from
|PEG.buildParser|. This will be used by plugins. The old way via setting
the |appliedPassNames| property is removed.
Implements part of GH-106.
Includes:
* Moving the source code from /src to /lib.
* Adding an explicit file list to package.json
* Updating the Makefile.
* Updating the spec and benchmark suites and their READMEs.
Part of a fix for GH-32.
David Majda
Arlo Breault