Measure load times; display on graph

[tfiers]

from

• Answer "how heavy is each of these deps?" #60 :

for installed in current project only
t₀=time(); @eval using $module; loadtime=time()-t₀
Just go down list (or up list rather. 'topological sort')
And done. Add to graph nodes (maybe fade the lower ones. Or ooh flame 🔥 color scheme!)

[tfiers]

Though hm I think you can't import a package that is, yes, in Manifest, but not in Projecr.

So maybe we run @time_imports in a subprocess and parse its text output 🤷

[tfiers]

Relevant:

• allow time_imports to return julia data that can be sorted and examined more easily JuliaLang/julia#47630

the macro just sets the Base.TIMING_IMPORTS flag.
(in stdlib, InteractiveUtils, macros.jl)

searching src:

• https://github.com/JuliaLang/julia/blob/e40d813/base/loading.jl#L934
  (search this file for timing_imports to see the code. elapsed = round((time_ns() - t_before) / 1e6, digits = 1))

My question is: is the last time reported the total time? Or of the root pkg only.
(It's not in docstr)

Relevant PRs:

• Add macro for timing package and dependency imports JuliaLang/julia#41612
• [Timing Imports] Use atomic_add! and atomic_sub! JuliaLang/julia#41737
• Add compilation & recompilation time to time_imports macro JuliaLang/julia#45064
• improve cache loading behaviors JuliaLang/julia#45861
  • This one removed the depth (commit nr 4: JuliaLang/julia@d0e28af)
• Format extensions with parent in @time_imports report JuliaLang/julia#47945

(the src for latest commit above is different than code in PR). So it's been rewritten from 1.8 to 1.9 or .10

[tfiers]

Again from src of main PR (https://github.com/JuliaLang/julia/pull/41612/files),
the test:

  redirect_stdout(buf) do
      @eval @time_imports using Foo3242
  end

So we don't need a sep process to read printed timings.
But I still will, cause some subdeps might already be imported.
(Confirmed in repl: re-running, e.g, @time_imports using UnicodePlots prints nothing the second time)

[tfiers]

And no, the numbers are not cumulative:

• docstring for @time_imports: explain what is shown (it's not cumulative) JuliaLang/julia#48248

(also not the last one -- notwithstanding what the example might imply; CSV really takes two seconds on its own)

[tfiers]

Proof of concept: 9ffab8e

[tfiers]

Next step is integrating into codebase.
A newline in the nodes (add an actual label)
maybe html node contents?

and then API.. a flag is fine (no sep function needed)

[tfiers]

• Check for at least Julia 1.8

[tfiers]

On integration:
I tried a start -- with

• Reorganize Internals #75:\

some files now capitalized; no more internals/ dir.
But that looked so messy

[tfiers]

• Try adding manually in webapp and looking at Graphviz example gallery

[tfiers]

So this got done in 95a1465.
[this and below comments moved to

• time_imports: dataviz (encode load-time graphically) #86

]