NJS variable access support.

[hongzhidao]

This PR is to introduce the feature of njs variable access. Here are 3 commits:

1. Generalize nxt_var_cache_value() to get variables via string names beside the reference index.
2. Introduce nxt_var_get() to access variables via string names, it'll be used in the next commit of access variables with njs.
3. njs variable access support.

Note, in the configuration, option values like some $uri text, and the part uri which is a variable name turned into an internal reference index for performance optimization. For the new feature, users can write JS code like ${uri} in the configuration, the script is parsed with njs library, so it can only access variable with a string name uri.

So we need to support two ways of accessing variables: ref index and string name.

[ac000]

Remember you should always provide at the very least a brief description of the PR...

[ac000]

OK. So before looking at the code there are a couple of issues.

1) Again these are using your @gmail address. 2) Commit message line length.

Fixing (1) will be tricky for all but the HEAD commit. For this I'd use git rebase -i...

For (2) NJS: variable access support. looks OK, however the others look well, a picture is worth a thousand words

So this is a standard 80 column terminal. We can see the first message is wrapped at around 72 characters, this is good, as you can see, git shows the commit message indented by 4 and so wrapping at 72 chars gives 4 characters of padding each side of the message.

NOTE: As you've seen we don't wrap things like URIs, command and log output etc...

Again this would be fixed via git rebase -i (there may be other ways, but that's what I would consider the standard/natural way to do it).

It would basically go like

$ git rebase -i HEAD~3

It will open your editor with the following

pick 44aac2b8 Var: generalized nxt_var_cache_value().                           
pick 2286f364 Var: introduced nxt_var_get().                                    
pick 9e510eb5 NJS: variable access support.                                     

# Rebase d9f5f1fb..9e510eb5 onto d9f5f1fb (3 commands)                          
#                                                                               
# Commands:                                                                     
# p, pick <commit> = use commit                                                 
# r, reword <commit> = use commit, but edit the commit message                  
# e, edit <commit> = use commit, but stop for amending                          
# s, squash <commit> = use commit, but meld into previous commit                
# f, fixup [-C | -c] <commit> = like "squash" but keep only the previous        
#                    commit's log message, unless -C is used, in which case     
#                    keep only this commit's message; -c is same as -C but      
#                    opens the editor                                           
# x, exec <command> = run command (the rest of the line) using shell            
# b, break = stop here (continue rebase later with 'git rebase --continue')     
# d, drop <commit> = remove commit                                              
# l, label <label> = label current HEAD with a name                             
# t, reset <label> = reset HEAD to a label                                      
# m, merge [-C <commit> | -c <commit>] <label> [# <oneline>]                    
#         create a merge commit using the original merge commit's               
#         message (or the oneline, if no original merge commit was              
#         specified); use -c <commit> to reword the commit message              
# u, update-ref <ref> = track a placeholder for the <ref> to be updated         
#                       to this position in the new commits. The <ref> is       
#                       updated at the end of the rebase                        
#                                                                               
# These lines can be re-ordered; they are executed from top to bottom.          
#                                                                               
# If you remove a line here THAT COMMIT WILL BE LOST.                           
#                                                                               
# However, if you remove everything, the rebase will be aborted.                
#

Now change those 'picks's to 'e's

e 44aac2b8 Var: generalized nxt_var_cache_value().                              
e 2286f364 Var: introduced nxt_var_get().                                       
e 9e510eb5 NJS: variable access support. 
...

Save and exit, you will then be dropped back to your shell.

It will start off with Var: generalized nxt_var_cache_value().

We can now do

$ git commit --amend --author="Zhidao HONG <z.hong@f5.com>"

Fix the commit message, save and exit

Now you can move onto the next commit

$ git rebase --continue
$ git commit --amend --author="Zhidao HONG <z.hong@f5.com>"

Fix the commit message, save and exit

Again, move onto the next (and final) commit

$ git rebase --continue
$ git commit --amend --no-edit --author="Zhidao HONG <z.hong@f5.com>"

Note, no real need to edit the last message.

Now to finish

$ git rebase --continue
Successfully rebased and updated refs/heads/hongzhidao-njs-var.

You can check the result with

$ git log --pretty=fuller

Then push this back to the PR

$ git push -f <remote> <branch>

[hongzhidao]

@ac000 Thanks, updated. And I'm not sure if I understand the message length correctly. I tried to use 72 chars as much as possible.

[ac000]

@ac000 Thanks, updated. And I'm not sure if I understand the message length correctly. I tried to use 72 chars as much as possible.

They look OK now, cheers.

I will probably have some questions about the changes themselves.

[hongzhidao]

Sure, we can call them Unit variables but not any JS variables. Unit native variables: https://unit.nginx.org/configuration/#variables Btw, in the template string, users can use any JS variables/functions/objects as well, they belong to the JS engine. For example:

{
    "pass": "`routes${uri + Math.random() * 100}`"
}

[ac000]

Sure, we can call them Unit variables but not any JS variables. Unit native variables: https://unit.nginx.org/configuration/#variables Btw, in the template string, users can use any JS variables/functions/objects as well, they belong to the JS engine. For example:

{
    "pass": "`routes${uri + Math.random() * 100}`"
}

Thanks. It's probably worth clarifying that in the commit message.

[ac000]

Btw, no need to terminate the subject lines with a full stop any more...

[hongzhidao]

Rebased and reworded the subjects.

[ac000]

commit a425506b178c7752933015d26deb43649947b6f1
Author: Zhidao HONG <z.hong@f5.com>
Date:   Wed Jan 31 14:08:57 2024 +0800

    Var: Refactored nxt_var_ref_get()

 delay         | 1135 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 src/nxt_var.c |   14 +-
 2 files changed, 1143 insertions(+), 6 deletions(-)
 create mode 100644 delay

Is still adding this delay file...

diff --git a/delay b/delay
new file mode 100644
index 00000000..85f32ec7
--- /dev/null
+++ b/delay

[hongzhidao]

commit a425506b178c7752933015d26deb43649947b6f1
Author: Zhidao HONG <z.hong@f5.com>
Date:   Wed Jan 31 14:08:57 2024 +0800

    Var: Refactored nxt_var_ref_get()

 delay         | 1135 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 src/nxt_var.c |   14 +-
 2 files changed, 1143 insertions(+), 6 deletions(-)
 create mode 100644 delay

Is still adding this delay file...

diff --git a/delay b/delay
new file mode 100644
index 00000000..85f32ec7
--- /dev/null
+++ b/delay

It's strange why there is such file left, I removed it, thanks.

[ac000]

Yeah, that looks better!

[valtzu]

Thanks for this great feature!

However, it seems quite buggy, it's only possible to use a single variable from vars since all the latter ones will get the same value as the 1st one. I imagine this has something to do with caching.

I have created an issue on this: #1169.