ToStringConsumer adds spurious newline to execInContainer outputs

When fetching stdout from an execInContainer Result object, an extra newline is added at the end of each frame. In our case, every 4097th char is a newline, which may break up a word.

The problem exists because ExecInContainerPattern.execInContainer() uses ToStringConsumer to collect stdout and stderr. Said classes adds a newline to before all but the first frame of data.

We need the exact output for our tests, and would appreciate a fix, or at least make this behavior configurable.

@weiminyu

Hey @weiminyu thanks for already investigating this, your description sounds valid.
With regards to #1763 it would be nice, if we could solve at a single point, to a bit more DRY.

Would you like to provide a PR for it?

@rnorth @bsideup Anything to add? It would be a "soft" breaking API change in case users are currently depending on this flawed behavior (which might very well be the case).

Update: the issue seems to have gone away by itself. Now I see the entire stdout passed as one OutputFrame to ToStringConsumer, and newline becomes a non-issue.

We did not upgrade testcontainer nor made any obviously related changes. Maybe this is a transitive dependency change wrt Docker?

Our output is less than 8K bytes. I'm unclear if the issue is fixed for all use cases However, for us this is no longer a pressing issue. Please feel free to close.

Thanks.

We see line breaks again in version 1.15.0-rc2. (Tested with Docker/Mac 2.3.0.5 and 2.4.0.0)

Testcase:

@Testcontainers
public class NewLineContainerTest {

    static class AlpineContainer extends GenericContainer<AlpineContainer> {
        public AlpineContainer() {
            super("alpine");
        }

        @Override
        protected void configure() {
            super.configure();
            this.withCommand("sleep", "2m");
        }
    }

    @Container
    private static final AlpineContainer container = new AlpineContainer();

    @Test
    public void test() throws Exception {
        String largeString = RandomStringUtils.randomAlphabetic(100000);
        System.out.println(largeString.contains("\n")); // returns false
        ExecResult build = container.execInContainer("echo", largeString);
        System.out.println(build.getStdout());
        System.out.println(build.getStdout().contains("\n")); // returns true
    }
}

Same here, upgrading from 1.14.3 to 1.15.1 makes a lot of our tests fail because of newline in the output that we never had before.

Remove extra newlines in container log output

@ReuDa

Thanks for the test case @ReuDa. I used it to create a unit test in this MR where I fixed this: #3752 (I hope this was fine with you, assuming the snippet you posted could be considered public domain).

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ToStringConsumer adds spurious newline to execInContainer outputs #1854

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ToStringConsumer adds spurious newline to execInContainer outputs #1854

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kiview commented on Dec 7, 2019

weiminyu commented on Jan 8, 2020

ReuDa commented on Oct 5, 2020

gaeljw commented on Dec 18, 2020

perlun commented on Feb 2, 2021

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