[PATCH] D68061: [docs] Document pattern of using CHECK-SAME to skip irrelevant lines

[Jordan Rupprecht via Phabricator via llvm-commits]

rupprecht added inline comments.


================
Comment at: llvm/docs/CommandGuide/FileCheck.rst:324
+would still pass because the "``CHECK: Value: 1``" line would match the value
+from ``baz``. To fix this, you could add ``CHECK-NEXT`` matchers for every
+``FieldN:`` line, but that would be verbose, and need to be updated when
----------------
greened wrote:
> This is what CHECK-LABEL is for.  This isn't a very motivating example.  Is there a better one?
I don't think CHECK-LABEL works in this case. CHECK-LABEL requires unique lines, and the only thing unique here would be "Name: <...>" which is not the thing we have a problem checking.

e.g. something like:
```
CHECK: Name: foo
CHECK-LABEL: Value: 1
```
would fail on the example text above because `foo` and `baz` both have a value of one. Similarly,
```
CHECK-LABEL: Name: foo
CHECK: Value: 1
```
has the same false-passing problem as described in these added docs.

Of course, you could add tests for every name/value pair (and using check-label on the names to make error messages clearer), but then the test overall becomes not a unit test: you really just want to write a unit test that verifies foo has a value of 1; you don't want to assert the universe to do that.

I don't use check-label very often, I'm mostly relying on docs for my understanding. Could you clarify your comment if I'm missing something? Also: if I'm not missing something, let me know how I can make the wording here more clear.


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