feat(loader): Make lazy-loading configurable

[AbhiPrasad]

ref getsentry/sentry#44225

As per the work in getsentry/sentry#44876, make lazy loading a injectable option.

See https://docs.sentry.io/platforms/javascript/install/lazy-load-sentry/#load-timing for more details on how this works.

[mydea]

Just to be clear, we still want this to be overwritable by the script tag here:

sentry-javascript/packages/browser/src/loader.js

Line 20 in 5b660cc

lazy = !(document.scripts[i].getAttribute('data-lazy') === 'no');

Or should we guard that to be basically:

var lazy = _lazy;

// if lazy is set to false, we cannot opt in?
if (lazy) {
  // check if option out of lazy
  for (...) {}
} 

Just thinking, because I guess it would kind of break in the case of performance/replay if this were to be overwritten to true again?

[AbhiPrasad]

Just to be clear, we still want this to be overwritable by the script tag here:

Yup, the script tag always supercedes this. Here are the scenarios:

1. lazy = true + data-lazy not set -> lazy == true (default for errors)
2. lazy = false + data-lazy not set -> lazy == false (default for replay + perf)
3. lazy = true + data-lazy === 'no' -> lazy == false
4. lazy = false + data-lazy === 'no -> lazy == false

[mydea]

2. lazy = false + data-lazy not set -> lazy == false (default for replay + perf)

but wouldn't this case, with the current code, lead to lazy == true? 🤔

[AbhiPrasad]

you're right 🤦 - I misunderstood the boolean condition ahhhhh

Let me change this

[AbhiPrasad]

Fixed with f09a965!

[github-actions]

size-limit report 📦

Path	Size
@sentry/browser - ES5 CDN Bundle (gzipped + minified)	20.11 KB (+0.22% 🔺)
@sentry/browser - ES5 CDN Bundle (minified)	62.49 KB (+0.31% 🔺)
@sentry/browser - ES6 CDN Bundle (gzipped + minified)	18.74 KB (+0.28% 🔺)
@sentry/browser - ES6 CDN Bundle (minified)	55.5 KB (+0.35% 🔺)
@sentry/browser - Webpack (gzipped + minified)	20.48 KB (+0.35% 🔺)
@sentry/browser - Webpack (minified)	66.94 KB (+0.28% 🔺)
@sentry/react - Webpack (gzipped + minified)	20.51 KB (+0.33% 🔺)
@sentry/nextjs Client - Webpack (gzipped + minified)	48.05 KB (+0.41% 🔺)
@sentry/browser + @sentry/tracing - ES5 CDN Bundle (gzipped + minified)	27.04 KB (+0.38% 🔺)
@sentry/browser + @sentry/tracing - ES6 CDN Bundle (gzipped + minified)	25.29 KB (+0.35% 🔺)
@sentry/replay ES6 CDN Bundle (gzipped + minified)	42.78 KB (+0.4% 🔺)
@sentry/replay - Webpack (gzipped + minified)	36.83 KB (+0.01% 🔺)
@sentry/browser + @sentry/tracing + @sentry/replay - ES6 CDN Bundle (gzipped + minified)	60.34 KB (+0.17% 🔺)
@sentry/browser + @sentry/replay - ES6 CDN Bundle (gzipped + minified)	53.91 KB (+0.12% 🔺)