Emscripten generates code that allows the caller to provide the Wasm
module (thorugh Module.instantiateWasm), with a fallback in case
.instantiateWasm is not provided. We always define instantiateWasm, so
we can hard-code the check and let our dead code elimination logic
remove the unused fallback.
This commit also improved the dead code elimination logic so that if
a function declaration becomes unused as a result of removing dead
code, the function itself is removed.
Note that we load all wasm-files manually, however the Emscripten Compiler (emcc) unfortunately generates `URL`s for fallback wasm-file loading.
In the PDF.js build-scripts we work-around that by using suitable Webpack-options, however that apparently doesn't work when third-party users re-bundle our code and we thus try to work-around this by adding "ignore comments" to these `URL`s (similar to how we handle `import`-statements).
Similar to Webpack there's apparently other bundlers that will not leave `import`-calls alone unless magic comments are used.
Hence we extend the builder to also append `/* @vite-ignore */` comments to `import`-calls, in order to attempt to improve support for using the PDF.js builds together with Vite.
This patch also renames `__non_webpack_import__` to `__raw_import__` since the functionality is no longer bundler-specific.
***PLEASE NOTE:*** This patch is provided as-is, and it does *not* mean that the PDF.js project can/will provide official support for Vite.
In order to fix bug 1935076, we'll have to add a pure js fallback in case wasm is disabled
or simd isn't supported. Unfortunately, this fallback will take some space.
So, the main goal of this patch is to reduce the overall size (by ~93k).
As a side effect, it should make easier to use an other wasm file (which must export
_jp2_decode, _malloc and _free).
JSON imports are now supported by all tools used in PDF.js' build
process. The `chromecom.js` file is bundled by webpack and
import attributes are thus removed, so browser compatibility for this
new syntax is not relevant.
Flat config is the new config system used by ESLint 9.
To make the migration easier, they also added
flat config support to ESLint 8.
This commit migrates the various ESLint configs in the repository to use
the new system, **without** upgrading to ESLint 9 yet.
Note that the new version of `eslint-plugin-import` contains support
for ESLint 9.
Moreover, the new version of Babel removed the leading space for import
comments (see https://github.com/babel/babel/pull/16780), so we update
the corresponding test expectation to match this.
Fixes a part of #17928.
We introduced quite a few new strings recently, but during the last few
rounds of updates we didn't see new translations updates becoming
available. I only just now recalled the announcement that Mozilla is
moving from Mercurial to Git, and indeed the Mercurial page at
https://hg.mozilla.org/l10n-central hasn't been updated since July
anymore and that's were we used to pull our translations from.
This commit fixes the issue by changing the URLs to the Mozilla Git
repositories hosted on GitHub instead.
This commit updates the Babel plugin to:
- apply the same flattening logic that we already
have for blocks, to flatten blocks nested inside
class static blocks
- remove class static blocks when, after flattening
all the blocks they contain, they are empty.
Before this commit, the transform output was the
same as the input.
When an image has a non-zero SMaskInData it means that the image
has an alpha channel.
With JPX images, the colorspace isn't required (by spec) so when we
don't have it, the JPX decoder will handle the conversion in RGBA
format.
This only happens when it's safe to do so. The exceptions are:
- when the class extends another subclass: removing the constructor would remove the error about the missing super() call
- when there are default parameters, that could have side effects
- when there are destructured prameters, that could have side effects
Given that the Fetch API is supported since Node.js 18 we should be able to use it when downloading l10n files, which allows us to simplify the code and to make it fully `async`.
Note how we're using custom `__non_webpack_import__`-calls in the code-base, that we replace during the post-processing stage of the build, to be able to write `import`-calls that Webpack will leave alone during parsing.
This work-around is necessary since we let Babel discards all comments, given that we generally don't need/want them in the builds, hence why we cannot utilize `/* webpackIgnore: true */`-comments in the source-code.
After the changes in PR 17563 it thus seems to me that we should be able to just move this re-writing into the Babel plugin instead.
Looking at the *built* files you'll notice some lines containing nothing more than a semicolon. This is the result of (mostly top-level) `if`-statements, which include `PDFJSDev`-checks, that evalute to `false` during Babel parsing.
This has always annoyed me a bit, and looking at Babel plugin it seems that we can fix this simply by *removing* the relevant nodes.
This part of the (modern) preprocessor is now dead code, since we no longer use `require` statements anywhere in the main code-base.
Note that as part of the changes leading up to PDF.js version `4` we removed all[1] the remaining `require` statements, and we also have an ESLint rule to ensure that no new ones are accidentally added.
---
[1] With two small exceptions, in benchmarking-code and in the Webpack-example.
All of our static evaluation & dead-code elimination transforms need to
happen in post-order, transforming inner nodes first. This is so that
in complex nested cases all transforms see the simplified version of
their inner nodes.
For example:
async getNimbusExperimentData() {
if (!PDFJSDev.test("GECKOVIEW")) { return null; }
// other code
}
-> [evaluation of PDFJSDev.*]
async getNimbusExperimentData() {
if (!false) { return null; }
// other code
}
-> [!false -> true]
async getNimbusExperimentData() {
if (true) { return null; }
// other code
}
-> [if (true) -> replace with the if branch]
async getNimbusExperimentData() {
return null;
// other code
}
-> [early return -> remove dead code]
async getNimbusExperimentData() {
return null;
// other code
}
This was done correctly in all cases except for our `UnaryExpression`
transform, which was happening in pre-order.
This commit converts the pdfjsdev-loader transform into a Babel plugin,
to skip a AST->string->AST round-trip.
Before this commit, the webpack build process was:
1. Babel parses the code
2. Babel transforms the AST
3. Babel generates the code
4. Acorn parses the code
5. pdfjsdev-loader transforms the AST
6. @javascript-obfuscator/escodegen generates the code
7. Webpack parses the file
8. Webpack concatenates the files
After this commit, it is reduced to:
1. Babel parses the code
2. Babel transforms the AST
3. babel-plugin-pdfjs-preprocessor transforms the AST
4. Babel generates the code
5. Webpack parses the file
6. Webpack concatenates the files
This change improves the build time by ~25% (tested on MacBook Air M2):
- `gulp lib`: 3.4s to 2.6s
- `gulp dist`: 36s to 29s
- `gulp generic`: 5.5s to 4.0s
- `gulp mozcentral`: 4.7s to 3.2s
The new Babel plugin doesn't support the `saveComments` option of
pdfjsdev-loader, and it just always discards comments. Even though
pdfjsdev-loader supported multiple values for that option, it was
effectively ignored due to `acorn` dropping comments by default.
This is in preparation for the next commit, which will convert
preprocessor2.mjs to a Babel plugin. The purpose of this commit
is to help git track the rename regardless of the large amount
of changes.
