Remove double parsing

[nirname]

📑 Summary

There is no issue on GH for it, but while researching the codebase I noticed that some diagrams are parsed twice, and this happens inside draw (render) function, which designation is to output data on the screen, not parsing.

📏 Details

• Removed some of parser.parse() calls, left those which are not so easy to remove at the first glance.
• Removed some unused comments

There are interesting comment about explicit parse calls. And I've been using some preliminary actions before parsing

My proposal is to:

• get rid of all parse calls
• add hooks instead (beforeRender, afterRender) etc...

📋 Tasks

Make sure you

• 📖 have read the contribution guidelines
• 💻 have added unit/e2e tests (if appropriate)
• 📓 have added documentation (if appropriate)
• 🔖 targeted develop branch

[codecov]

Codecov Report

Merging #4587 (d5021ca) into develop (1b190b2) will increase coverage by 21.70%.
The diff coverage is n/a.

Additional details and impacted files

@@             Coverage Diff              @@
##           develop    #4587       +/-   ##
============================================
+ Coverage    58.12%   79.83%   +21.70%     
============================================
  Files           52      143       +91     
  Lines         8667    16487     +7820     
  Branches        18      518      +500     
============================================
+ Hits          5038    13162     +8124     
+ Misses        3629     3220      -409     
- Partials         0      105      +105     

Flag	Coverage Δ
e2e	83.95% <ø> (?)
unit	58.12% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
packages/mermaid/src/diagrams/er/erRenderer.js	93.47% <ø> (ø)
...ckages/mermaid/src/diagrams/gantt/ganttRenderer.js	87.24% <ø> (ø)
...es/mermaid/src/diagrams/mindmap/mindmapRenderer.js	98.27% <ø> (ø)
packages/mermaid/src/diagrams/pie/pieRenderer.js	89.23% <ø> (ø)
...id/src/diagrams/requirement/requirementRenderer.js	92.96% <ø> (ø)
.../mermaid/src/diagrams/timeline/timelineRenderer.ts	96.39% <ø> (ø)
...rmaid/src/diagrams/user-journey/journeyRenderer.ts	84.67% <ø> (ø)

... and 130 files with indirect coverage changes

[nirname]

I am not sure what to do with

• flowRenderer-elk
• flowchart and additional functions inside it
• the same is about flowchart-v2 and its functions (https://github.com/mermaid-js/mermaid/blob/develop/packages/mermaid/src/diagrams/flowchart/flowRenderer-v2.js#L346-L356)
• state v2
• and sequence (some tests fail there)

Git blame suggests to ask @knsv about this, because I am relatively new to the code base

[nirname]

I know this is a small step towards standard form for diagrams, but it is better not to have double parsing wherever it is possible

[sidharthv96]

LGTM.
Shouldn't be an issue as long as the tests pass.