Queries with recursive predicates do not parse

[mpoffald]

Our expand fn is throwing an exception when we attempt to parse queries with recursive predicates.

Exception is being thrown at this step: https://github.com/fluree/db/blob/main/src/fluree/db/query/fql/parse.cljc#L144

Stack trace:

  contains? not supported on type: clojure.lang.Keyword

                   RT.java:  853  clojure.lang.RT/contains
                  core.clj: 1506  clojure.core/contains?
                  core.clj: 1498  clojure.core/contains?
               expand.cljc:  319  fluree.json_ld.impl.expand$node/invokeStatic
               expand.cljc:  305  fluree.json_ld.impl.expand$node/invoke
               expand.cljc:  311  fluree.json_ld.impl.expand$node/invokeStatic
               expand.cljc:  305  fluree.json_ld.impl.expand$node/invoke
              json_ld.cljc:   96  fluree.json_ld$expand/invokeStatic
              json_ld.cljc:   88  fluree.json_ld$expand/invoke
                parse.cljc:  145  fluree.db.query.fql.parse$recursion_predicate/invokeStatic
                parse.cljc:  134  fluree.db.query.fql.parse$recursion_predicate/invoke
                parse.cljc:  210  fluree.db.query.fql.parse$parse_recursion_predicate/invokeStatic
                parse.cljc:  208  fluree.db.query.fql.parse$parse_recursion_predicate/invoke
                parse.cljc:  235  fluree.db.query.fql.parse$parse_predicate_pattern/invokeStatic
                parse.cljc:  230  fluree.db.query.fql.parse$parse_predicate_pattern/invoke
                parse.cljc:  293  fluree.db.query.fql.parse$parse_triple/invokeStatic
                parse.cljc:  290  fluree.db.query.fql.parse$parse_triple/invoke
                parse.cljc:  307  fluree.db.query.fql.parse$eval30336$fn__30337/invoke
              MultiFn.java:  244  clojure.lang.MultiFn/invoke
                parse.cljc:  284  fluree.db.query.fql.parse$parse_where_clause$fn__30328/invoke
                  core.clj: 6979  clojure.core/mapv/fn
           ArrayChunk.java:   58  clojure.lang.ArrayChunk/reduce
             protocols.clj:  136  clojure.core.protocols/fn
             protocols.clj:  124  clojure.core.protocols/fn
             protocols.clj:   19  clojure.core.protocols/fn/G
             protocols.clj:   31  clojure.core.protocols/seq-reduce
             protocols.clj:   75  clojure.core.protocols/fn
             protocols.clj:   75  clojure.core.protocols/fn
             protocols.clj:   13  clojure.core.protocols/fn/G
                  core.clj: 6886  clojure.core/reduce
                  core.clj: 6970  clojure.core/mapv
                  core.clj: 6970  clojure.core/mapv
                parse.cljc:  283  fluree.db.query.fql.parse$parse_where_clause/invokeStatic
                parse.cljc:  279  fluree.db.query.fql.parse$parse_where_clause/invoke
                parse.cljc:  327  fluree.db.query.fql.parse$parse_where/invokeStatic
                parse.cljc:  324  fluree.db.query.fql.parse$parse_where/invoke
                parse.cljc:  394  fluree.db.query.fql.parse$parse_analytical_query/invokeStatic
                parse.cljc:  389  fluree.db.query.fql.parse$parse_analytical_query/invoke
subject_crawl_reparse_test.clj:   97  fluree.db.query.subject-crawl-reparse-test/fn
subject_crawl_reparse_test.clj:    9  fluree.db.query.subject-crawl-reparse-test/fn
                  test.clj:  242  cider.nrepl.middleware.test/test-var/fn
                  test.clj:  242  cider.nrepl.middleware.test/test-var
                  test.clj:  234  cider.nrepl.middleware.test/test-var
                  test.clj:  257  cider.nrepl.middleware.test/test-vars/fn/fn
                  test.clj:  687  clojure.test/default-fixture
                  test.clj:  683  clojure.test/default-fixture
                  test.clj:  257  cider.nrepl.middleware.test/test-vars/fn
                  test.clj:  687  clojure.test/default-fixture
                  test.clj:  683  clojure.test/default-fixture
                  test.clj:  254  cider.nrepl.middleware.test/test-vars
                  test.clj:  248  cider.nrepl.middleware.test/test-vars
                  test.clj:  270  cider.nrepl.middleware.test/test-ns
                  test.clj:  261  cider.nrepl.middleware.test/test-ns
                  test.clj:  281  cider.nrepl.middleware.test/test-var-query
                  test.clj:  274  cider.nrepl.middleware.test/test-var-query
                  test.clj:  319  cider.nrepl.middleware.test/handle-test-var-query-op/fn/fn
                  AFn.java:  152  clojure.lang.AFn/applyToHelper
                  AFn.java:  144  clojure.lang.AFn/applyTo
                  core.clj:  667  clojure.core/apply
                  core.clj: 1990  clojure.core/with-bindings*
                  core.clj: 1990  clojure.core/with-bindings*
               RestFn.java:  425  clojure.lang.RestFn/invoke
                  test.clj:  311  cider.nrepl.middleware.test/handle-test-var-query-op/fn
                  AFn.java:   22  clojure.lang.AFn/run
               session.clj:  218  nrepl.middleware.session/session-exec/main-loop/fn
               session.clj:  217  nrepl.middleware.session/session-exec/main-loop
                  AFn.java:   22  clojure.lang.AFn/run
               Thread.java:  833  java.lang.Thread/run

[bplatz]

Here is a property path description from SPARQL which ultimately we want to support all of - so we should use similar syntax (JSON-ified): https://en.wikibooks.org/wiki/SPARQL/Property_paths

[dpetran]

Possibly related: db #322

[mpoffald]

This still does need some spec work to see what syntax we can use that won't break anything, but that will be part of the implementation work.

[mpoffald]

Some work was done on this, but the approach needs to be rethought and this isn't high-priority enough to keep working on right now.

The fix for the parsing error itself is straightforward, just need to use expand-iri where we were using expand, and accommodate strings vs keywords appropriately: https://github.com/fluree/db/commit/d943ba225c4209daf25aa59d4ec049242df27229

But the bigger lift is getting the recursive queries to actually execute, and we have chosen to come back to that later.