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syntax: don't pick up chan chains (channel of channels) #678
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FTR: this introduces a regression; more details in my comment in #655 |
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Hi @fxkr Thanks for testing it! I've force pushed the changes you mentioned. Can you please try again? |
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This is a very weird error. We want to show an error if the chan statement is in form of: <- chan chan <- The correct form should be of course: <-chan chan<- But for example, if we have a channel of channels (like below), the selected piece of whitespace is also highlighted as an error chan<- chan<- ^ Because it's the part of `<- chan`, whereas we should not treat as an error because we have two `chan<-` and `chan<-` statements. To fix this, we add a `negative lookbehind` regex statement. It will not match a text if it's preceded with other text. First let assemble the current regex for the case: `<- chan` (receive-only annotation), which is: \(<-\)\@<=\s\+\(chan\>\)\@= The first part is: \(<-\)\@<=\s\+\ Here the pattern \@<= matches with zero width if the preceding atom matches just before what follows. `\s\+` means white space of at least one character. So it matches **whitespaces** which precedes the statement `<-` Now the second part is only useful with the first part. I've added the placeholder to make it more readable: PLACEHOLDER(chan\>\)\@=" First the pattern `\@=` means to match the preceding atom with zero width. So it will match the **PLACEHOLDER** till it finds a `chan` statement. Once it finds it, it doesn't proceed anymore. So we only highlight the whitespaces between `<-` and `chan` only if we have a white space of at least one character Finally we can introduce our fix now. We're going to pick the `<-` statemetn if it doesn't follow a `chan`. So `chan<-` should NOT trigger an error anymore, because we're not going to pick arrows in that form. To match an arrow which doesn't follow a chan statement can be done via a `negative lookbehind`, which is in the form of: \(\<chan\>\)\@<!<- This literally means: "Match `<-` only if it doesn't follow `chan`. We're going to use this pattern for the plain `<-` pattern. We also fix the issue of only matching `chan` and not words like `mychan`. Aslo note we're just going to replace this into our current regex: This original regex: \(<-\)\@<=\s\+\(\<chan\>\)\@= will be changed into: \(\(\<chan\>\)\@<!<-\)\@<=\s\+\(\<chan\>\)\@= Fixes #655
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@fxkr fixed. Nice catch, seems I've accidentally added it. |
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syntax: don't pick up chan chains (channel of channels)
Thanks @fxkr for the feedback. Please open a issue if you find other cases. |
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Fixes the following wrong highlighting:
into:
This is a very weird error. We want to show an error if the chan
statement is in form of:
The correct form should be of course:
But for example, if we have a channel of channels (like below), the
selected piece of whitespace is also highlighted as an error
Because it's the part of
<- chan
, whereas we should not treat as anerror because we have two
chan<-
andchan<-
statements.To fix this, we add a
negative lookbehind
regex statement. It will notmatch a text if it's preceded with other text.
First let assemble the current regex for the case:
<- chan
(receive-only annotation), which is:
The first part is:
Here the pattern @<= matches with zero width if the preceding atom
matches just before what follows.
\s\+
means white space of at leastone character. So it matches whitespaces which precedes the
statement
<-
Now the second part is only useful with the first part. I've added the
placeholder to make it more readable:
First the pattern
\@=
means to match the preceding atom with zerowidth. So it will match the PLACEHOLDER till it finds a
chan
statement. Once it finds it, it doesn't proceed anymore. So we only
highlight the whitespaces between
<-
andchan
only if we have awhite space of at least one character
Finally we can introduce our fix now. We're going to pick the
<-
statemetn if it doesn't follow a
chan
. Sochan<-
should NOT triggeran error anymore, because we're not going to pick arrows in that form.
To match an arrow which doesn't follow a chan statement can be done via
a
negative lookbehind
, which is in the form of:This literally means: "Match
<-
only if it doesn't followchan
.We're going to use this pattern for the plain
<-
pattern. Not we'rejust going to replace this into our current regex:
This original regex:
will be changed into:
Fixes #655