C#: Extract string interpolation alignment and format. #19089
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michaelnebel
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| import csharp | ||
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| query predicate inserts(InterpolatedStringExpr expr, Expr e) { | ||
| expr.getAnInsert() = e // and inSpecificSource(expr) |
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| } | ||
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| query predicate texts(InterpolatedStringExpr expr, StringLiteral literal) { | ||
| expr.getAText() = literal // and inSpecificSource(expr) |
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| where | ||
| expressions(e, k, t) and | ||
| if k = 138 then kind = 106 else kind = k | ||
| select e, kind, t |
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Should this select the insert part of e instead of e?
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I considered doing that as well, but it requires that we also make changes to the expr_parent relation as well (this is what I am vaguely hinting in the PR description).
Basically, I am worried that I break some DB invariant by changing the parent/child relationship as a part of the script.
Should we attempt to make the better downgrade script? It requires
(1) Removing the insert expressions from the expressions relation
(2) Adjust the expr_parent relation
(3) Consider if we need to do something with the new dangling align and format expressions.
This PR fixes an issue with missing extraction of alignment and format clauses from string interpolation expressions as described here.
Prior to this change, when we extracted a string interpolation expression
$"Hello {name,align:format}. Welcome."(denotedEin the graphs below), it looked like this in the expressions relationWith this change we introduce a new expression for `{name:align:format}, which we call a string interpolation insert expression. The expression tree for extracting a string interpolation expression now looks like,
graph TD; id1["#quot;Hello #quot;"] id2["{name,align:format}"] id3["#quot;. Welcome.#quot;"] id4["name"] id5["align"] id6["format"] E--0-->id1 E--1-->id2 E--2-->id3 id2--0-->id4 id2--1-->id5 id2--2-->id6This change in the expression tree of string interpolation expressions makes it impossible/difficult to make a proper upgrade/downgrade script, as we introduce a new kind of expression and alter the parent/child relationship. That is, to make a proper upgrade script, we would need to introduce new expressions and alter- and add new entries in the expressions and expr_parent relations. We might be able to do it a bit better in the downgrade script, but I have chosen just to change the kind of the expressions to unknown.
Effectively, this change means that we break dataflow for string interpolation expressions, when the upgrade and downgrade scripts are used.
Another alternative could have been to make a tree like
graph TD; id1["#quot;Hello #quot;"] id2["name"] id3["{align:format}"] id4["#quot;. Welcome.#quot;"] E--0-->id1 E--1-->id2 E--2-->id3 E--3-->id4This would make it easier to make backwards compatible upgrade- and downgrade scripts, but I think the chosen design is better as it more closely resembles the structure of the code.
Other relevant implementation details
nameto{name,align:format}in the example.DCA looks un-eventfull.