gitea/templates/repo
wxiaoguang 5b89670a31
Use a general Eval function for expressions in templates. (#23927)
One of the proposals in #23328

This PR introduces a simple expression calculator
(templates/eval/eval.go), it can do basic expression calculations.

Many untested template helper functions like `Mul` `Add` can be replaced
by this new approach.

Then these `Add` / `Mul` / `percentage` / `Subtract` / `DiffStatsWidth`
could all use this `Eval`.

And it provides enhancements for Golang templates, and improves
readability.

Some examples:

----

* Before: `{{Add (Mul $glyph.Row 12) 12}}`
* After: `{{Eval $glyph.Row "*" 12 "+" 12}}`

----

* Before: `{{if lt (Add $i 1) (len $.Topics)}}`
* After: `{{if Eval $i "+" 1 "<" (len $.Topics)}}`

## FAQ

### Why not use an existing expression package?

We need a highly customized expression engine:

* do the calculation on the fly, without pre-compiling
* deal with int/int64/float64 types, to make the result could be used in
Golang template.
* make the syntax could be used in the Golang template directly
* do not introduce too much complex or strange syntax, we just need a
simple calculator.
* it needs to strictly follow Golang template's behavior, for example,
Golang template treats all non-zero values as truth, but many 3rd
packages don't do so.

### What's the benefit?

* Developers don't need to add more `Add`/`Mul`/`Sub`-like functions,
they were getting more and more.
Now, only one `Eval` is enough for all cases.
* The new code reads better than old `{{Add (Mul $glyph.Row 12) 12}}`,
the old one isn't familiar to most procedural programming developers
(eg, the Golang expression syntax).
* The `Eval` is fully covered by tests, many old `Add`/`Mul`-like
functions were never tested.

### The performance?

It doesn't use `reflect`, it doesn't need to parse or compile when used
in Golang template, the performance is as fast as native Go template.

### Is it too complex? Could it be unstable?

The expression calculator program is a common homework for computer
science students, and it's widely used as a teaching and practicing
purpose for developers. The algorithm is pretty well-known.

The behavior can be clearly defined, it is stable.
2023-04-07 21:25:49 +08:00
..
actions Use data-tooltip-content for tippy tooltip (#23649) 2023-03-24 18:35:38 +08:00
branch Use a general Eval function for expressions in templates. (#23927) 2023-04-07 21:25:49 +08:00
cite Use data-tooltip-content for tippy tooltip (#23649) 2023-03-24 18:35:38 +08:00
diff Use a general Eval function for expressions in templates. (#23927) 2023-04-07 21:25:49 +08:00
editor Use a general Eval function for expressions in templates. (#23927) 2023-04-07 21:25:49 +08:00
find Refactor hiding-methods, remove jQuery show/hide, remove .hide class, remove inline style=display:none (#22950) 2023-02-19 12:06:14 +08:00
graph Use a general Eval function for expressions in templates. (#23927) 2023-04-07 21:25:49 +08:00
issue Refactor authors dropdown (send get request from frontend to avoid long wait time) (#23890) 2023-04-07 08:11:02 +08:00
migrate Remove incorrect HTML self close tag (#23748) 2023-03-27 18:05:51 +02:00
projects Introduce GiteaLocaleNumber custom element to handle number localization on pages. (#23861) 2023-04-03 12:58:09 -04:00
pulls Remove incorrect HTML self close tag (#23748) 2023-03-27 18:05:51 +02:00
release Title can be empty when creating tag only (#23917) 2023-04-06 21:44:52 -04:00
settings Fix code view (diff) broken layout (#23096) 2023-04-04 19:05:07 +08:00
wiki Use a general Eval function for expressions in templates. (#23927) 2023-04-07 21:25:49 +08:00
activity.tmpl Add context when rendering labels or emojis (#23281) 2023-03-05 22:59:05 +01:00
blame.tmpl Use data-tooltip-content for tippy tooltip (#23649) 2023-03-24 18:35:38 +08:00
branch_dropdown.tmpl Refactor branch/tag selector to Vue SFC (#23421) 2023-03-14 17:51:20 +08:00
clone_buttons.tmpl Clean template/helper.go (#23922) 2023-04-07 03:31:41 -04:00
clone_script.tmpl Clean template/helper.go (#23922) 2023-04-07 03:31:41 -04:00
commit_page.tmpl Remove incorrect HTML self close tag (#23748) 2023-03-27 18:05:51 +02:00
commit_status.tmpl Use different SVG for pending and running actions (#23836) 2023-03-31 17:24:39 +08:00
commit_statuses.tmpl Fix hidden commit status on multiple checks (#22889) 2023-02-20 16:43:04 +08:00
commits_list_small.tmpl Use a general Eval function for expressions in templates. (#23927) 2023-04-07 21:25:49 +08:00
commits_list.tmpl Add context when rendering labels or emojis (#23281) 2023-03-05 22:59:05 +01:00
commits_table.tmpl Use data-tooltip-content for tippy tooltip (#23649) 2023-03-24 18:35:38 +08:00
commits.tmpl Move helpers to be prefixed with gt- (#22879) 2023-02-13 17:59:59 +00:00
create_helper.tmpl Add templates to customize text when creating and migrating repositories 2023-01-24 22:36:48 -05:00
create.tmpl Remove incorrect HTML self close tag (#23748) 2023-03-27 18:05:51 +02:00
empty.tmpl Add main landmark to templates and adjust titles (#22670) 2023-02-01 22:56:10 +00:00
file_info.tmpl Use data-tooltip-content for tippy tooltip (#23649) 2023-03-24 18:35:38 +08:00
forks.tmpl Remove fomantic ".link" selector and styles (#23888) 2023-04-03 20:47:23 -04:00
graph.tmpl Refactor hiding-methods, remove jQuery show/hide, remove .hide class, remove inline style=display:none (#22950) 2023-02-19 12:06:14 +08:00
header.tmpl Use data-tooltip-content for tippy tooltip (#23649) 2023-03-24 18:35:38 +08:00
home.tmpl Use a general Eval function for expressions in templates. (#23927) 2023-04-07 21:25:49 +08:00
icon.tmpl Move helpers to be prefixed with gt- (#22879) 2023-02-13 17:59:59 +00:00
packages.tmpl Add main landmark to templates and adjust titles (#22670) 2023-02-01 22:56:10 +00:00
search_name.tmpl Clean template/helper.go (#23922) 2023-04-07 03:31:41 -04:00
search.tmpl Use data-tooltip-content for tippy tooltip (#23649) 2023-03-24 18:35:38 +08:00
shabox_badge.tmpl Fix shabox regression (#22924) 2023-02-16 09:37:11 +08:00
sub_menu.tmpl Remove fomantic ".link" selector and styles (#23888) 2023-04-03 20:47:23 -04:00
unicode_escape_prompt.tmpl Convert <div class="button"> to <button class="button"> (#23337) 2023-03-14 11:34:09 +08:00
upload.tmpl Refactor i18n to locale (#20153) 2022-06-27 15:58:46 -05:00
user_cards.tmpl Add context cache as a request level cache (#22294) 2023-02-15 21:37:34 +08:00
view_file.tmpl Use a general Eval function for expressions in templates. (#23927) 2023-04-07 21:25:49 +08:00
view_list.tmpl Add wrapper to author to avoid long name ui problem (#23030) 2023-02-23 14:28:18 -06:00
watchers.tmpl Add main landmark to templates and adjust titles (#22670) 2023-02-01 22:56:10 +00:00