R Shiny breaks PostgreSQL authentication with .pgpass - r

Question

I have my password to database stored in pgpass.conf file. I am connecting to database from R with RPostgres, without specifying password so it is read from pgpass.conf, like this:
con <- dbConnect(RPostgres::Postgres(),
dbname = "dbname",
user = "username",
host = "localhost",
port = "5432")
It usually works perfectly, however when I try to connect to database from shiny app it doesn't work. Connection definition is exactly the same as above and placed in server.R script. When I run Shiny app with default arguments I get an error:
FATAL: password authentication failed for user "username"
password retrieved from file "C:\Users\...\AppData\Roaming/postgresql/pgpass.conf"
When password is explicitly given in connection definition:
con <- dbConnect(RPostgres::Postgres(),
dbname = "dbname",
user = "username",
host = "localhost",
password = "mypass",
port = "5432")
everything works.
To make things stranger, when port for shiny is set to some value, for example: shiny::runApp(port = 4000), connection is established without specifying password, but ONLY for the first time - that means when app is closed and reopened in the same R session, the error occurs again.
I've tested package 'RPostgreSQL' - it doesn't work neither, only error message is different:
Error in postgresqlNewConnection(drv, ...) :
RS-DBI driver: (could not connect postgres#localhost on dbname "dbname")
I use 32-bit R but I've tested it on 64-bit and it was the same. Shiny app was run both in browser (Chrome) and in Rstudio Viewer.
Here my session info:
R version 3.2.2 (2015-08-14)
Platform: i386-w64-mingw32/i386 (32-bit)
Running under: Windows 7 x64 (build 7601) Service Pack 1
locale:
[1] LC_COLLATE=Polish_Poland.1250 LC_CTYPE=Polish_Poland.1250 LC_MONETARY=Polish_Poland.1250
[4] LC_NUMERIC=C LC_TIME=Polish_Poland.1250
attached base packages:
[1] stats graphics grDevices utils datasets methods base
other attached packages:
[1] RPostgres_0.1 DBI_0.3.1.9008 shiny_0.12.2
loaded via a namespace (and not attached):
[1] R6_2.1.1 htmltools_0.2.6 tools_3.2.2 rstudioapi_0.3.1 Rcpp_0.12.1.3 jsonlite_0.9.17 digest_0.6.8
[8] xtable_1.7-4 httpuv_1.3.3 mime_0.4 RPostgreSQL_0.4

Answer 1

There's likely something different about the environment in which the command is run between Shiny and your system R GUI. I get around this by storing my credentials in an Renviron file:
readRenviron("~/.Renviron")
con <- dbConnect(RPostgres::Postgres(),
dbname = Sys.getenv('pg_db'),
user = Sys.getenv('api_user'),
...)
The thing about that is you could maintain separate Renvirons for staging and production environments. This allows your script to take a commandArgs() to specify which DB credentials it should use:
#!/usr/bin/env Rscript
environ_path <- switch(commandArgs(),
'staging' = {"~/staging.Renviron"},
'production' = {"~/production/Renviron"})
readRenviron(environ_path)
Then from BASH:
Rscript analysis.R staging

Answer 2

The Error is in Postgresql:
C:\Users\...\AppData\Roaming/postgresql/pgpass.conf
the file path contains "/" instead of "\"