piped fetch prop not working as expected for multiple edge pattern

[wey-gu]

Please check the FAQ documentation before raising an issue

The multiple edge pattern like the following:

(root@nebula) [basketballplayer]> FETCH PROP ON serve "player100" -> "team204", "player133" -> "team202" YIELD edge AS e;
+-----------------------------------------------------------------------+
| e                                                                     |
+-----------------------------------------------------------------------+
| [:serve "player100"->"team204" @0 {end_year: 2016, start_year: 1997}] |
| [:serve "player133"->"team202" @0 {end_year: 2011, start_year: 2002}] |
+-----------------------------------------------------------------------+
Got 2 rows (time spent 3285/9989 us)

doesn't work in this case:

(root@nebula) [basketballplayer]> go from "player100" over follow yield id($$) as alliasId, "player102" as v3 | FETCH PROP ON follow $-.alliasId -> $-.v3@0 YIELD properties(edge);
+------------------+
| properties(EDGE) |
+------------------+
| {degree: 90}     |
+------------------+
Got 1 rows (time spent 9009/23040 us)

(root@nebula) [basketballplayer]> go from "player100" over follow yield id($$) as alliasId, "player102" as v3 | FETCH PROP ON follow $-.alliasId -> $-.v3, $-.alliasId -> $-.v3@1 YIELD properties(edge);
[ERROR (-1004)]: SyntaxError: syntax error near `, $-.all'

Describe the bug (required)

As above, only edge_key_ref in singular case was implemented for now.

edge_key_ref
    : input_prop_expression R_ARROW input_prop_expression AT input_prop_expression {
        $$ = new EdgeKeyRef($1, $3, $5);
    }
    | input_prop_expression R_ARROW input_prop_expression AT constant_expression {
        $$ = new EdgeKeyRef($1, $3, $5);
    }
    | var_prop_expression R_ARROW var_prop_expression AT var_prop_expression {
        $$ = new EdgeKeyRef($1, $3, $5, false);
    }
    | var_prop_expression R_ARROW var_prop_expression AT constant_expression {
        $$ = new EdgeKeyRef($1, $3, $5, false);
    }
    | input_prop_expression R_ARROW input_prop_expression {
        $$ = new EdgeKeyRef($1, $3, ConstantExpression::make(qctx->objPool(), 0));
    }
    | var_prop_expression R_ARROW var_prop_expression {
        $$ = new EdgeKeyRef($1, $3, ConstantExpression::make(qctx->objPool(), 0), false);
    }
    ;

fetch_edges_sentence
    : KW_FETCH KW_PROP KW_ON name_label_list edge_keys yield_clause {
        auto fetch = new FetchEdgesSentence($4, $5, $6);
        $$ = fetch;
    }
    | KW_FETCH KW_PROP KW_ON name_label_list edge_key_ref yield_clause {
        auto fetch = new FetchEdgesSentence($4, $5, $6);
        $$ = fetch;
    }
    ;

Your Environments (required)

• OS: uname -a
• Compiler: g++ --version or clang++ --version
• CPU: lscpu
• Commit id 3.0

How To Reproduce(required)

as above

Expected behavior

Additional context

#4188

[wey-gu]

Another thing is that we only support either both or non peer of the fetch prop edge pattern to be variable, that is.
we only support:

• fetch on serve "player133" -> "team202"
• yield "foo" as a, "bar" as bar | fetch on serve $-.a -> $-.b

while not support :

• yield "foo" as a, "bar" as bar | fetch on serve $-.a -> "bar"

reported in #4191

[wey-gu]

Mitigation for now was to use union