This repo demonstrates an issue with objection.js when attempting to include it in a minified bundle using esbuild.
Some features of
objection.js,
when used in code that is bundled and minified, will throw an exception like
the following
[Note: some other minified identifier may appear in the place of Fj
]:
TypeError: Class constructor Fj cannot be invoked without 'new'
In the example in this repo, the error is thrown when attempting to use
the joinRelated
method of the
objection.js
Model
class.
For representative class definitions that will trigger the error, see
lines 7-30 of example.js
.
The representative query can be found on line 82 of example.js
.
How to re-create the issue
- Clone this repo
- Install dependencies (e.g.
yarn install
ornpm install
) - Run the package scripts
yarn test
ornpm run test
to bundle and run the minified example code and exhibit the error.yarn unminified
ornpm run unminified
to bundle and run the example code without minification and without error.yarn partial
ornpm run partial
to bundle and run the example code with whitespace and syntax minification, but without identifier minification (no error).
Each of the package scripts bundles example.js
using the build.js
file
to call esbuild
(with varying states of minification), and then runs the
resulting bundle to demonstrate the effect of the minification.
Explanation of the issue
The issue appears to be in knexUtils.js
(lines 39-39)
Notice that the checks for
isKnexQueryBuilder
, isKnexJoinBuilder
, and isKnexRaw
look for a specific constructor using a literal string value.
This comparison is bound to fail when the identifiers being compared against
have been minified.
Potential solutions/work-arounds
-
The first solution is to avoid minifying the code, with the obvious downside being a larger bundle size. Of course the impact will vary depending on the project, but for this example (where the majority of the code is objection.js and knex ) the unminified bundle is twice the size of the minified bundle.
-
The second solution is to partially minify the code by utilizing the more granular
--minify-whitespace
and--minify-syntax
options of esbuild instead of the more general--minify
option (i.e. avoiding identifier minification which can be seperately controlled via the--minify-identifiers
option). This will avoid the issue while still providing some reduction in the size of the bundle (though less reduction than with full minification). -
The third possible solution is to modify the code in objection.js so that a string literal is not used to complete the checks within
isKnexQueryBuilder
,isKnexJoinBuilder
, andisKnexRaw
found inknexUtils.js
Here are three potential modifications that could be made:-
The obvious solution is to utilize
instanceof
to see if the variable is an instance of the appropriate class. However, this is not possible because the classes of interest are internal to knex and are not publicly exported. So, the first potential modification is to modify knex so that theBuilder
,JoinClause
andRaw
classes are exported publicly, so that the appropriate identifier is used even when minified. Then the objection.jsknexUtils.js
checks could be modified similar to:import { JoinClause } from 'knex' function isKnexJoinBuilder(value) { return value instanceof JoinClause; }
Note that this requires changes within both knex and objection.js
-
The next possibility restricts changes to within the objection.js file
knexUtils.js
where theisKnexQueryBuilder
,isKnexJoinBuilder
, andisKnexRaw
functions could utilize unique properties of each knex class to identify instances of each. While it may not be required, you could also still ensure that each has a constructor (just not a specific constructor), e.g.function hasConstructor(value) { return isObject(value) && isFunction(value.constructor); }
And then check for the existence of fields unique to each class, e.g.
function isKnexQueryBuilder(value) { return ( hasConstructor(value) && isFunction(value.select) && isFunction(value.column) && value.select === value.column && 'client' in value ); }
See knex/lib/query/querybuilder.js:L1452-L1453
function isKnexJoinBuilder(value) { return hasConstructor(value) && value.grouping === 'join' && 'joinType' in value; }
See knex/lib/query/joinclause.js:L237-L239
function isKnexRaw(value) { return hasConstructor(value) && value.isRawInstance && 'client' in value; }
See knex/lib/raw.js:L131-L132
Note that these changes rely on the internals of knex (i.e. not part of the public API), and therefore could be subject to change. -
Another possibility makes changes to knex as well as objection.js such that each instance of these classes has a property which identifies it's type. For example, the
Raw
knex class already has a flag (isRawInstance
) that is used internally within knex and could be relied on to identify instances of each class (see above). Similarly, anisBuilderInstance
flag could be added toBuilder
and anisJoinClauseInstance
flag could be added toJoinClause
. Then the appropriate modifications (similar to those above) could be made within objection.js. This change would essentially be a request to make these flags part of the official public API of knex, rather than exporting the internal classes.
-