Subject: Re: [PATCH] userdiff: Fix some corner cases in dts regex

From: Stephen Boyd <[email-masked]>
Date: Tue, 08 Oct 2019 07:43:05 -0700

Quoting Johannes Sixt (2019-10-05 07:09:11)
> Am 04.10.19 um 23:30 schrieb Stephen Boyd:
> > While reviewing some dts diffs recently I noticed that the hunk header
> > logic was failing to find the containing node. This is because the regex
> > doesn't consider properties that may span multiple lines, i.e.
> > 
> >       property = <something>,
> >                  <something_else>;
> 
> What if the property spans more than two lines?
> 
>         property = <something>,
>                    more,
>                    <something_else>;
> 
> Can the second line "more," begin with a word, or are the angle brackets
> mandatory?

Angle brackets aren't mandatory, but it is very odd to have a property
with mixed numbers and strings because parsing becomes difficult.

> 
> I understand that the continuation lines can begin with a word when the
> property is an expression that is distributed over a number of lines.
> Such continuation lines could be picked up as hunk headers.
> 
> But I don't want to complicate things: The hunk header patterns do not
> have to be perfect; it is sufficient when they are helpful in a good
> majority of cases that occur in practice.
> 
> > and it got hung up on comments inside nodes that look like the root node
> > because they start with '/*'. Add tests for these cases and update the
> > regex to find them. Maybe detecting the root node is too complicated but
> > forcing it to be a backslash with any amount of whitespace up to an open
> > bracket seemed OK. I tried to detect that a comment is in-between the
> > two parts but I wasn't happy so I just dropped it.
> > 
> > Cc: Rob Herring <[email-masked]>
> > Cc: Frank Rowand <[email-masked]>
> > Signed-off-by: Stephen Boyd <[email-masked]>
> > ---
> >  t/t4018/dts-nodes-multiline-prop | 12 ++++++++++++
> >  t/t4018/dts-root                 |  2 +-
> >  t/t4018/dts-root-comment         |  8 ++++++++
> >  userdiff.c                       |  3 ++-
> >  4 files changed, 23 insertions(+), 2 deletions(-)
> >  create mode 100644 t/t4018/dts-nodes-multiline-prop
> >  create mode 100644 t/t4018/dts-root-comment
> > 
> > diff --git a/t/t4018/dts-nodes-multiline-prop b/t/t4018/dts-nodes-multiline-prop
> > new file mode 100644
> > index 000000000000..f7b655935429
> > --- /dev/null
> > +++ b/t/t4018/dts-nodes-multiline-prop
> > @@ -0,0 +1,12 @@
> > +/ {
> > +     label_1: node1@ff00 {
> > +             RIGHT@deadf00,4000 {
> > +                     multilineprop = <3>,
> > +                                     <4>;
> 
> You could insert more lines to demonstrate that "<x>," on a line by
> itself is not picked up.

Maybe I should add another test?

> 
> > +
> > +
> > +> +                  ChangeMe = <0xffeedd00>;
> 
> Sufficient distance to the incorrect candidates above. Good.
> 
> > +             };
> > +     };
> > +};
> > diff --git a/t/t4018/dts-root b/t/t4018/dts-root
> > index 2ef9e6ffaa2c..4353b8220c91 100644
> > --- a/t/t4018/dts-root
> > +++ b/t/t4018/dts-root
> > @@ -1,4 +1,4 @@
> > -/RIGHT { /* Technically just supposed to be a slash */
> > +/ { RIGHT /* Technically just supposed to be a slash and brace */
> 
> Do I understand correctly that the updated form, "/ {", is the common
> way to spell a root node, but "/" or "/word" are not?

Correct. A root node is '/' and the '{' opens the node. There is the
possibility of something like '/delete-node nodename;' or
'/delete-property property;', where the latter exists inside some node.
The regex would need to avoid all of those.

> 
> >       #size-cells = <1>;
> >  
> >       ChangeMe = <0xffeedd00>;
> > diff --git a/t/t4018/dts-root-comment b/t/t4018/dts-root-comment
> > new file mode 100644
> > index 000000000000..333a625c7007
> > --- /dev/null
> > +++ b/t/t4018/dts-root-comment
> > @@ -0,0 +1,8 @@
> > +/ { RIGHT /* Technically just supposed to be a slash and brace */
> 
> Devil's advocate here: insert ';' or '=' in the comment, and the line
> would not be picked up. Does that hurt in practice?

I don't think it hurts in practice so I'd like to ignore it.

> 
> > +     #size-cells = <1>;
> > +
> > +     /* This comment should be ignored */
> > +
> > +     some-property = <40+2>;
> > +     ChangeMe = <0xffeedd00>;
> > +};
> > diff --git a/userdiff.c b/userdiff.c
> > index 86e3244e15dd..651b56caec56 100644
> > --- a/userdiff.c
> > +++ b/userdiff.c
> > @@ -25,8 +25,9 @@ IPATTERN("ada",
> >        "|=>|\\.\\.|\\*\\*|:=|/=|>=|<=|<<|>>|<>"),
> >  PATTERNS("dts",
> >        "!;\n"
> > +      "!.*=.*\n"
> 
> This behaves the same way as just
> 
>         "!=\n"
> 
> no?
> 

Not exactly. Properties don't always get assigned. There are boolean
properties that can be tested for by the presence of some string with an
ending semi-colon, like 'this-is-true;'. If we just check for not equal
to a line with a semicolon and newline then we'll see boolean
properties. Should I add that as another test?