FIX: entrez_post does not use POST method for >200 IDs

[allenbaron]

When args$id is present as input to make_entrez_query() (e.g. from entrez_post) the IDs are collapsed to a string (length = 1) before args$id length > 200 is used to determine whether to use the POST method. It always uses the GET method because it's always length <= 1.

This is a minor change that fixes this issue. It passes your testthat::test() with 4 warnings. May need to be combined with PR #164 if implementing fix for Issue #163.

Reprex - Original code

library(rentrez)

pmid <- 25348409

# Get PubMed articles PMIDs that cite pmid (234)
citedin_pmids <- rentrez::entrez_link(
    dbfrom = "pubmed",
    id = pmid,
    db = "pubmed",
    linkname = "pubmed_pubmed_citedin"
)$links$pubmed_pubmed_citedin


# Try to create web history with epost ------------------------------------

# even GET method works above 200 (using 234 IDs)
rentrez::entrez_post(
    db = "pubmed",
    id = citedin_pmids,
    web_history = NULL
)
#> Web history object (QueryKey = 1, WebEnv = MCID_6127c75...)

# but not around ~500 (using 468 IDs)
ids_rep2 <- rep(citedin_pmids, 2)
rentrez::entrez_post(
    db = "pubmed",
    id = ids_rep2,
    web_history = NULL
)
#> Error in entrez_check(response): HTTP failure 414, the request is too large. For large requests, try using web history as described in the rentrez tutorial

Created on 2021-08-26 by the reprex package (v2.0.1)

Reprex - After fix

library(rentrez)

pmid <- 25348409

# Get PubMed articles PMIDs that cite pmid (234)
citedin_pmids <- rentrez::entrez_link(
    dbfrom = "pubmed",
    id = pmid,
    db = "pubmed",
    linkname = "pubmed_pubmed_citedin"
)$links$pubmed_pubmed_citedin


# Try to create web history with epost ------------------------------------

# even GET method works above 200 (using 234 IDs)
rentrez::entrez_post(
    db = "pubmed",
    id = citedin_pmids,
    web_history = NULL
)
#> Web history object (QueryKey = 1, WebEnv = MCID_6127cb8...)

# but not around ~500 (using 468 IDs) --> NOW WORKS
ids_rep2 <- rep(citedin_pmids, 2)
rentrez::entrez_post(
    db = "pubmed",
    id = ids_rep2,
    web_history = NULL
)
#> Web history object (QueryKey = 1, WebEnv = MCID_6127cb8...)

Created on 2021-08-26 by the reprex package (v2.0.1)