Prerender doesn't use the build options setting for the default "index.html" name

[vmasek]

🐞 Bug report

Prerender builder seems to ignore the build options setting the default "index.html" name/location.

What modules are related to this issue?

• builders

Is this a regression?

No

Description

From what I've seen the prerender

🔬 Minimal Reproduction

1. Rename your index.html to something else, for example: index.original.html
2. Set the correct name in angular.json configuration for projects.name.architect.build.options.index
   • in this case "index": "src/index.original.html",
3. Try to prerender your application

🔥 Exception or Error

An unhandled exception occurred: ENOENT: no such file or directory, open 'C:\Users\user-name\WebstormProjects\my-project\dist\browser\index.html'

This is expected as dist\browser\index.html does not exist, but dist\browser\index.original.html does.

Possible solution

Replacing browserIndexOutputPath at line https://github.com/angular/universal/blob/f0a78c4792ebd6e4e920cda60552be123f7c6810/modules/builders/src/prerender/index.ts#L111
with path.join(outputPath, 'index.original.html') seems to fix the error, but only the "default" route is rendered and I don't even have it specified in routes I want to render.

It would be ideal if the prerender builder respected the setting set in the build options.

I'm open to PR but I need guidance determining the best solution and on how to get the builder options to the _renderUniversal function.

🌍 Your Environment

Angular CLI: 9.1.0
Node: 12.16.1
OS: win32 x64

Angular: 9.1.0
... animations, cli, common, compiler, compiler-cli, core, forms
... language-service, platform-browser, platform-browser-dynamic
... platform-server, router
Ivy Workspace: Yes

Package                           Version
-----------------------------------------------------------
@angular-devkit/architect         0.900.6
@angular-devkit/build-angular     0.901.0
@angular-devkit/build-optimizer   0.901.0
@angular-devkit/build-webpack     0.901.0
@angular-devkit/core              9.0.6
@angular-devkit/schematics        9.1.0
@angular/cdk                      9.2.0
@angular/flex-layout              9.0.0-beta.29
@ngtools/webpack                  9.1.0
@nguniversal/builders             9.0.2
@nguniversal/common               9.0.2
@nguniversal/express-engine       9.0.2
@schematics/angular               9.1.0
@schematics/update                0.901.0
rxjs                              6.5.4
typescript                        3.8.3
webpack                           4.42.0

[wagnermaciel]

Hey @vmasek, thank you for your bug report. I don't believe this was ever an option for the prerender builder. You can see the list of options that the prerender builder has available by viewing schema.ts or schema.json.

@alan-agius4 I do think this is a perfectly valid feature request, though. What are your thoughts?

[alan-agius4]

Indeed this is a bug as this line

universal/modules/builders/src/prerender/index.ts

Line 110 in f0a78c4

const browserIndexOutputPath = path.join(outputPath, 'index.html');

is using a hard coded to use index.html and not using the index value from the options provided in browser builder.

[wagnermaciel]

Ah, I see. I did not catch that this option was coming from the browser builder. Thank you for the clarification!

[wagnermaciel]

I have a fix for this - Should be ready by tomorrow 👍

[wagnermaciel]

Hey, just discussed this with Minko and we quickly realized that the expected behavior here might not be so clear.

@vmasek can you provide some clarification on why users change the default html document? I want to familiarize myself with this use case before trying to make this change.

Also, I'd like to hear your opinions on what should happen if a user sets their base html document as "src/home.html" and tries to prerender the route "/". Should we prerender it as "home.html"?

[alan-agius4]

I think the following option should be honoured https://github.com/angular/angular-cli/blob/29660aa8edf23c416c8c82677136b642c4992c2d/packages/angular_devkit/build_angular/src/browser/schema.json#L293

Meaning the input/output of the index should be gather from this option.

I don’t know that’s the usecase in this case for changing the index file but I did see in the past different indexes for different environments, themes etc..

[wagnermaciel]

I agree that the index option from angular_devkit should continue to be used, but the question still stands - if someone has sets the index option to point to a different file (e.g. "src/home.html") should prerendering the route "/" generate the static file for "home.html" or "index.html"?

[alan-agius4]

The pretending behaviour shouldn’t change.

The difference is the the input file and the output file name.

Let’s take this offline.

[vmasek]

@wagnermaciel It might be fixable by some workaround.

My use-case is this.

There is a website served by a cloud function. on the base root "/" it automatically detects a preferred language and redirects to that language route.

Code example for express server

  server.get('/', (req: express.Request, res: express.Response): void => {
    if (req.acceptsLanguages('cs', 'sk')) {
      res.redirect(302, '/cs/homepage');
    } else {
      res.redirect(302, `/en/homepage`);
    }
  });

So for the base "/" route we don't want any HTML response, just the redirect.

Express static server will server the "/" route with the /index.html if not disabled in config.
There are two possibilities to solve this. Disable it or rename the index Angular uses to render app.
But we cannot disable only the base /index.html, it disables all of them, so no pre-rendering with this disabled.

If we rename the "base" index, we will end up at this problem.

What I thought of as a workaround would be to exclude "/" route and the rename the /index.html in dist after the pre-rendering has been done to /index.original.html. Or include the "/" route (don't care about what it renders), it will create the "original" and than we remove what was rendered in the base /index.html in dist so it is not picked up by the static serve.

[wagnermaciel]

@alan-agius4 It seems like the express-engine server does not honored this feature. See how in express-engine's server.ts schematic we only render using "index" or "index.original.html". The same issue is true for hapi-engine's server.ts schematic.

Is this something we can expect the user to change when they use the browser builder's index option, or should this be automatic?