graphviz errors in scaladocs for 2.12

[raboof]

graphviz produces errors during the generation of embedded svgs in the 2.12 scaladocs.

you can reproduce this with e.g. sbt ++2.12 persistence-tck/doc.

diagnosing by adding -diagrams-debug to the scaladoc options in project/Doc.scala, we get some more diagnostics:

model contains 36 documentable templates

**********************************************************************
The graphviz dot diagram tool has malfunctioned and will be restarted.

The following is the log of the failure:
  DOT <error console>: malloc_consolidate(): unaligned fastbin chunk detected

  Cleanup: Last template: org.apache.pekko.persistence.journal.JournalPerfSpec
  Cleanup: Last dot input: 
    digraph G {
    compound="true";
    rankdir="TB";
    node [margin="0.08,0.01", fontsize="8.00", style="filled,rounded", height="0.0", penwidth="1", shape="rect", width="0.0", fontname="Source Code Pro"];
    edge [arrowsize="0.7", fontcolor="#aaaaaa", fontsize="9.00", color="#d4d4d4", fontname="Source Code Pro"];
    subgraph clusterAll {
    style="invis"
    subgraph clusterOutgoing {
    style="invis"
    node6 [label=<<TABLE BORDER="0" CELLBORDER="0"><TR><TD><IMG SCALE="TRUE" SRC="/home/aengelen/dev/apache/incubator-pekko/persistence-tck/target/scala-2.12/api/lib/class_diagram.png" /></TD><TD VALIGN="MIDDLE">scalatest.matchers.should.Matchers.Equalizer[JournalPerfSpec] </TD></TR></TABLE>>,fontcolor="#7d7d7d", color="#ababab", id="implicit-outgoing class|graph1_6", fillcolor="#e1e1e1", tooltip="org.apache.pekko.persistence.journal.JournalPerfSpec can be implicitly converted to scalatest.matchers.should.Matchers.Equalizer[JournalPerfSpec] by the implicit method convertToEqualizer in trait org.scalactic.TripleEquals"];
    node5 [label=<<TABLE BORDER="0" CELLBORDER="0"><TR><TD><IMG SCALE="TRUE" SRC="/home/aengelen/dev/apache/incubator-pekko/persistence-tck/target/scala-2.12/api/lib/class_diagram.png" /></TD><TD VALIGN="MIDDLE">scalatest.matchers.should.Matchers.AnyShouldWrapper[JournalPerfSpec] </TD></TR></TABLE>>,fontcolor="#7d7d7d", color="#ababab", id="implicit-outgoing class|graph1_5", fillcolor="#e1e1e1", tooltip="org.apache.pekko.persistence.journal.JournalPerfSpec can be implicitly converted to scalatest.matchers.should.Matchers.AnyShouldWrapper[JournalPerfSpec] by the implicit method convertToAnyShouldWrapper in trait org.scalatest.matchers.should.Matchers"];
    node4 [label=<<TABLE BORDER="0" CELLBORDER="0"><TR><TD><IMG SCALE="TRUE" SRC="/home/aengelen/dev/apache/incubator-pekko/persistence-tck/target/scala-2.12/api/lib/class_diagram.png" /></TD><TD VALIGN="MIDDLE">scalactic.TripleEquals.Equalizer[JournalPerfSpec] </TD></TR></TABLE>>,fontcolor="#7d7d7d", color="#ababab", id="implicit-outgoing class|graph1_4", fillcolor="#e1e1e1", tooltip="org.apache.pekko.persistence.journal.JournalPerfSpec can be implicitly converted to scalactic.TripleEquals.Equalizer[JournalPerfSpec] by the implicit method convertToEqualizer in trait org.scalactic.TripleEquals"];
    node3 [label=<<TABLE BORDER="0" CELLBORDER="0"><TR><TD><IMG SCALE="TRUE" SRC="/home/aengelen/dev/apache/incubator-pekko/persistence-tck/target/scala-2.12/api/lib/class_diagram.png" /></TD><TD VALIGN="MIDDLE">scalatest.Assertions.Equalizer[JournalPerfSpec] </TD></TR></TABLE>>,fontcolor="#7d7d7d", color="#ababab", id="implicit-outgoing class|graph1_3", fillcolor="#e1e1e1", tooltip="org.apache.pekko.persistence.journal.JournalPerfSpec can be implicitly converted to scalatest.Assertions.Equalizer[JournalPerfSpec] by the implicit method convertToEqualizer in trait org.scalactic.TripleEquals"];
    node3 -> node4 -> node5 -> node6 [constraint="false", style="invis", minlen="0.0"];
    }
    subgraph clusterThis {
    style="invis"
    node0 [label=<<TABLE BORDER="0" CELLBORDER="0"><TR><TD><IMG SCALE="TRUE" SRC="/home/aengelen/dev/apache/incubator-pekko/persistence-tck/target/scala-2.12/api/lib/class_diagram.png" /></TD><TD VALIGN="MIDDLE">JournalPerfSpec </TD></TR></TABLE>>,fontcolor="#ffffff", URL="#inheritance-diagram", color="#418565", id="this class|graph1_0", fillcolor="#418565", tooltip="org.apache.pekko.persistence.journal.JournalPerfSpec (this class)"];
    }
    
    node0 -> node3 [id="implicit-outgoing|0_3", tooltip="JournalPerfSpec can be implicitly converted to scalatest.Assertions.Equalizer[JournalPerfSpec], scalactic.TripleEquals.Equalizer[JournalPerfSpec], scalatest.matchers.should.Matchers.AnyShouldWrapper[JournalPerfSpec], scalatest.matchers.should.Matchers.Equalizer[JournalPerfSpec]", constraint="false", minlen="2", ltail="clusterThis", lhead="clusterOutgoing", label="implicitly"];
    }
    node1 [label=<<TABLE BORDER="0" CELLBORDER="0"><TR><TD><IMG SCALE="TRUE" SRC="/home/aengelen/dev/apache/incubator-pekko/persistence-tck/target/scala-2.12/api/lib/class_diagram.png" /></TD><TD VALIGN="MIDDLE">JavaJournalPerfSpec </TD></TR></TABLE>>,fontcolor="#ffffff", URL="../japi/journal/JavaJournalPerfSpec.html#inheritance-diagram", color="#418565", id="class|graph1_1", fillcolor="#418565", tooltip="org.apache.pekko.persistence.japi.journal.JavaJournalPerfSpec"];
    node2 [label=<<TABLE BORDER="0" CELLBORDER="0"><TR><TD><IMG SCALE="TRUE" SRC="/home/aengelen/dev/apache/incubator-pekko/persistence-tck/target/scala-2.12/api/lib/class_diagram.png" /></TD><TD VALIGN="MIDDLE">JournalSpec </TD></TR></TABLE>>,fontcolor="#ffffff", URL="JournalSpec.html#inheritance-diagram", color="#418565", id="class|graph1_2", fillcolor="#418565", tooltip="org.apache.pekko.persistence.journal.JournalSpec"];
    node2 -> node0 [id="inheritance|graph1_2_0", tooltip="JournalPerfSpec is a subtype of JournalSpec", dir="back", arrowtail="empty"];
    node0 -> node1 [id="inheritance|graph1_0_1", tooltip="JavaJournalPerfSpec is a subtype of JournalPerfSpec", dir="back", arrowtail="empty"];
    }

  Cleanup: Dot path: dot
  Cleanup: Dot exit code: 134
**********************************************************************
Graphviz will be restarted...


Diagram generation running time breakdown:

  diagrams model filtering
  ========================
    count:        72 items
    total time:   0 ms
    average time: 0 ms
    maximum time: 0 ms

  diagrams model generation
  =========================
    count:        72 items
    total time:   10 ms
    average time: 0 ms
    maximum time: 2 ms

  dot diagram generation
  ======================
    count:        21 items
    total time:   6 ms
    average time: 0 ms
    maximum time: 1 ms

  dot process running
  ===================
    count:        21 items
    total time:   387 ms
    average time: 18 ms
    maximum time: 277 ms

  svg processing
  ==============
    count:        21 items
    total time:   81 ms
    average time: 3 ms
    maximum time: 28 ms

  Broken images: 94
  Fixed images: 0

I'm using graphviz 9.0.0, and passing that graph to dot manually works fine. Also 2.13 docs appear to be fine.

Perhaps we should just disable scaladoc diagrams for 2.12?