Emphasize user code in stack traces

[dandv]

Creating a new issue after discussion in #24002.

I’d like to propose a feature to improve readability when working with stack traces. Currently, assertion errors generate a verbose stack trace that includes both user code and internal library or runtime code. It can be challenging to quickly locate the lines relevant to my own logic amidst calls from the Deno standard library or third-party modules.

Failed assertions would be a good start for this feature, given stack traces are gnarly enough that a flag was created to hide them.

error: AssertionError: Values are not strictly equal.


    [Diff] Actual / Expected


-   5
+   3

  throw new AssertionError(message);
        ^
    at assertStrictEquals (https://jsr.io/@std/assert/1.0.10/strict_equals.ts:66:9)
    at toBe (https://jsr.io/@std/expect/1.0.10/_matchers.ts:29:5)
    at applyMatcher (https://jsr.io/@std/expect/1.0.10/expect.ts:223:13)
    at Proxy.<anonymous> (https://jsr.io/@std/expect/1.0.10/expect.ts:233:13)
    at checkQueueAndResults (file:///home/dandv/project/tests/common.ts:187:39) ⬅️
    at Object.runMicrotasks (ext:core/01_core.js:683:26)
    at processTicksAndRejections (ext:deno_node/_next_tick.ts:59:10)
    at runNextTicks (ext:deno_node/_next_tick.ts:76:3)
    at eventLoopTick (ext:core/01_core.js:182:21)
    at async Object.<anonymous> (file:///home/dandv/project/tests/unit.test.ts:349:7) ⬅️

Proposal

– Highlight or visually distinguish user code in the stack trace, for example with a marker like ⬅️ (since bold and colors are already used)

– Either hide references to the Deno and library calls, or de-emphasize them (greyed out?) so they don’t obscure the code paths I’m actively debugging.