1583109 - Add utility function for joining a sequence of strings with a separator

Status: RESOLVED FIXED

(Core :: XPCOM, enhancement)

Description

[Simon Giesecke [:sg] [he/him]]

A utility function for joining a sequence of strings with a separator would be helpful (along the lines of https://www.boost.org/doc/libs/1_71_0/boost/algorithm/string/join.hpp).

For a sequence that is a standard C++ range, this might be implemented (with proper templating) using

std::accumulate(sequence.cbegin(), sequence.cend(), nsCString{}, 
    [](nsCString &str, const nsCString &item) -> decltype(auto) { return s += item; });

In addition to the basic variant, a function accepting a functor that appends to the result string on each iteration, would also be helpful, which can be called like this:

nsTArray<int> sequence = {1, 2, 3};
const auto res = StringJoin(sequence, NS_LITERAL_CSTRING(", "), [](nsCString& str, int item) { str. Append('"'); str.AppendInt(item); str. Append('"');  });

resulting in res == NS_LITERAL_CSTRING("\"1\", \"2\", \"3\"").

Besides sequences that are standard C++ ranges, the utility functions should also work with containers such as nsTHashtable via ConstIter (or nsTHashtable is made a C++ range as well).

Comment 1

[Simon Giesecke [:sg] [he/him]]

Attachment: Bug 1583109 - Add StringJoin(Append) utility functions that join a sequence of items into a string. r=#xpcom-reviewers

Comment 2

[Simon Giesecke [:sg] [he/him]]

Attachment: Bug 1583109 - Use StringJoin(Append) where easily possible.

Depends on D98749

Comment 3

[Simon Giesecke [:sg] [he/him]]

nsTHashtable is a C++ range now.

Comment 4

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/c7bcdc88920a
Add StringJoin(Append) utility functions that join a sequence of items into a string. r=xpcom-reviewers,nika

Comment 5

[Sebastian Hengst [:aryx] (needinfo me if it's about an intermittent or backout)]

https://hg.mozilla.org/mozilla-central/rev/c7bcdc88920a

Comment 6

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/16d174e7c342
Use StringJoin(Append) where easily possible. r=nika

Comment 7

[Natalia Csoregi [:nataliaCs]]

Backed out for causing bustage on nsReadableUtils.h

backout: https://hg.mozilla.org/integration/autoland/rev/36e58b614815fb3da6d7840d6f787b6ec2eed618

push: https://treeherder.mozilla.org/jobs?repo=autoland&revision=16d174e7c342ad3e0add694a67d35b868e90f19a&group_state=expanded

failure log: https://treeherder.mozilla.org/logviewer?job_id=324743715&repo=autoland&lineNumber=6468

[task 2020-12-16T20:31:27.455Z] 20:31:27 INFO - In file included from /builds/worker/workspace/obj-build/dist/include/nsString.h:18:
[task 2020-12-16T20:31:27.455Z] 20:31:27 ERROR - /builds/worker/workspace/obj-build/dist/include/nsReadableUtils.h:456:15: error: loop variable 'item' is always a copy because the range of type 'const mozilla::EnumSet<unsigned long, unsigned long>' does not return a reference [-Werror,-Wrange-loop-analysis]
[task 2020-12-16T20:31:27.455Z] 20:31:27 INFO - for (auto&& item : aInputRange) {
[task 2020-12-16T20:31:27.456Z] 20:31:27 INFO - ^
[task 2020-12-16T20:31:27.456Z] 20:31:27 INFO - /builds/worker/workspace/obj-build/dist/include/nsReadableUtils.h:484:3: note: in instantiation of function template specialization 'StringJoinAppend<char, mozilla::EnumSet<unsigned long, unsigned long>, (lambda at /builds/worker/workspace/obj-build/dist/include/mozilla/dom/SyncedContextInlines.h:25:21)>' requested here
[task 2020-12-16T20:31:27.456Z] 20:31:27 INFO - StringJoinAppend(res, aSeparator, aInputRange, std::forward<Func>(aFunc));
[task 2020-12-16T20:31:27.456Z] 20:31:27 INFO - ^
[task 2020-12-16T20:31:27.456Z] 20:31:27 INFO - /builds/worker/workspace/obj-build/dist/include/mozilla/dom/SyncedContextInlines.h:38:23: note: in instantiation of function template specialization 'mozilla::dom::syncedcontext::FormatValidationError<mozilla::dom::BrowsingContext>' requested here
[task 2020-12-16T20:31:27.456Z] 20:31:27 INFO - nsCString error = FormatValidationError<Context>(
[task 2020-12-16T20:31:27.456Z] 20:31:27 INFO - ^
[task 2020-12-16T20:31:27.456Z] 20:31:27 INFO - /builds/worker/workspace/obj-build/dist/include/nsReadableUtils.h:456:8: note: use non-reference type 'unsigned long'
[task 2020-12-16T20:31:27.457Z] 20:31:27 INFO - for (auto&& item : aInputRange) {
[task 2020-12-16T20:31:27.458Z] 20:31:27 INFO - ^~~~~~~~~~~~~
[task 2020-12-16T20:31:27.458Z] 20:31:27 ERROR - /builds/worker/workspace/obj-build/dist/include/nsReadableUtils.h:456:15: error: loop variable 'item' is always a copy because the range of type 'const mozilla::EnumSet<unsigned long, unsigned long>' does not return a reference [-Werror,-Wrange-loop-analysis]
[task 2020-12-16T20:31:27.458Z] 20:31:27 INFO - for (auto&& item : aInputRange) {
[task 2020-12-16T20:31:27.458Z] 20:31:27 INFO - ^
[task 2020-12-16T20:31:27.458Z] 20:31:27 INFO - /builds/worker/workspace/obj-build/dist/include/nsReadableUtils.h:484:3: note: in instantiation of function template specialization 'StringJoinAppend<char, mozilla::EnumSet<unsigned long, unsigned long>, (lambda at /builds/worker/workspace/obj-build/dist/include/mozilla/dom/SyncedContextInlines.h:25:21)>' requested here
[task 2020-12-16T20:31:27.458Z] 20:31:27 INFO - StringJoinAppend(res, aSeparator, aInputRange, std::forward<Func>(aFunc));
[task 2020-12-16T20:31:27.458Z] 20:31:27 INFO - ^

Comment 8

[Natalia Csoregi [:nataliaCs]]

Also failing: https://treeherder.mozilla.org/logviewer?job_id=324747022&repo=autoland&lineNumber=1852

Comment 9

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/2556404e58f7
Use StringJoin(Append) where easily possible. r=nika

Comment 10

[Cosmin Sabou [:CosminS]]

https://hg.mozilla.org/mozilla-central/rev/2556404e58f7