Lockdir prefix for install packages

Some distributed file systems do not support opening files in append
mode. These file systems are often used in data analysis cloud
platforms.

R package installation relies on appending to files, for instance
collating R code or when installing help pages.

Therefore, packages can't be installed in those filesystems. Instead,
users are forced to install packages into a local directory and
copy them afterwards.

However, the current package installation procedure already uses
a 00LOCK directory to install packages there, before copying them
to the final library directory.

By globally modifying the location of the 00LOCK directory, it is
possible to use a local filesystem to install packages, where
append is allowed. The installation process takes care of copying
the resulting package into the final out directory.

This change introduces the environment variable PKG_LOCKDIR_PREFIX
that, when set to a directory like "/tmp/r-lockdir", uses that
root path to create all 00LOCK folders.

This allows to install packages on file systems that do not support
opening files in append mode.

Author: Sergio Oller Moreno

src/library/tools/R/install.R

@@ -54,7 +54,23 @@ if(FALSE) {
 
     ## global variables
     curPkg <- character() # list of packages in current pkg
+
+	## Path to where lockdirs will be created. If empty, use lib directory
+	lockdir_prefix <- Sys.getenv("PKG_LOCKDIR_PREFIX", "")
+	if (lockdir_prefix == "")
+        lockdir_prefix <- NULL
+    else
+        lockdir_prefix <- path.expand(lockdir_prefix)
+	## The lockdir, relative to lockdir_prefix
     lockdir <- ""
+    ## The lockdir, including the prefix
+    lockdir_with_prefix <- ""
+    get_lockdir_with_prefix <- function(lockdir) {
+        if (!is.null(lockdir_prefix))
+            file.path(lockdir_prefix, lockdir)
+        else
+            lockdir
+    }
     is_first_package <- TRUE
     stars <- "*"
     user.tmpdir <- Sys.getenv("PKG_BUILD_DIR")
@@ -105,8 +121,8 @@ if(FALSE) {
             }
 
             if (nzchar(lockdir) &&
-                dir.exists(lp <- file.path(lockdir, curPkg)) &&
-                is_subdir(lp, lockdir)) {
+                dir.exists(lp <- file.path(lockdir_with_prefix, curPkg)) &&
+                is_subdir(lp, lockdir_with_prefix)) {
                 starsmsg(stars, "restoring previous ", sQuote(pkgdir))
                 if (WINDOWS) {
                     file.copy(lp, dirname(pkgdir), recursive = TRUE,
@@ -134,7 +150,7 @@ if(FALSE) {
             if (lib == .Library && "html" %in% build_help_types)
                 utils::make.packages.html(.Library, docdir = R.home("doc"))
         }
-        if (nzchar(lockdir)) unlink(lockdir, recursive = TRUE)
+        if (nzchar(lockdir_with_prefix)) unlink(lockdir_with_prefix, recursive = TRUE)
     }
 
     do_cleanup_tmpdir <- function()
@@ -478,7 +494,7 @@ if(FALSE) {
         if (file.exists(file.path(instdir, "DESCRIPTION"))) {
             if (nzchar(lockdir))
                 system(paste("mv -f", shQuote(instdir),
-                             shQuote(file.path(lockdir, pkg))))
+                             shQuote(file.path(lockdir_with_prefix, pkg))))
             dir.create(instdir, recursive = TRUE, showWarnings = FALSE)
         }
         TAR <- Sys.getenv("TAR", 'tar')
@@ -1041,9 +1057,9 @@ if(FALSE) {
                     if (more_than_libs) unlink(instdir, recursive = TRUE)
                 } else if (more_than_libs)
                     system(paste("mv -f ", shQuote(instdir),
-                                 shQuote(file.path(lockdir, pkg_name))))
+                                 shQuote(file.path(lockdir_with_prefix, pkg_name))))
                 else
-                    file.copy(instdir, lockdir, recursive = TRUE,
+                    file.copy(instdir, lockdir_with_prefix, recursive = TRUE,
                               copy.date = TRUE)
             } else if (more_than_libs) unlink(instdir, recursive = TRUE)
             if (more_than_libs && dir.exists(instdir))
@@ -1073,10 +1089,10 @@ if(FALSE) {
             final_rlibs <- Sys.getenv("R_LIBS")
             final_libpaths <- .libPaths()
 
-            instdir <- file.path(lockdir, "00new", pkg_name)
+            instdir <- file.path(lockdir_with_prefix, "00new", pkg_name)
             Sys.setenv(R_PACKAGE_DIR = instdir)
             dir.create(instdir, recursive = TRUE, showWarnings = FALSE)
-            lib <- file.path(lockdir, "00new")
+            lib <- file.path(lockdir_with_prefix, "00new")
 
             rlibs <- if (nzchar(final_rlibs))
                          paste(lib, final_rlibs, sep = .Platform$path.sep)
@@ -2373,7 +2389,8 @@ if(FALSE) {
     }
     if (lock && !pkglock) {
         lockdir <- file.path(lib, "00LOCK")
-        mk_lockdir(lockdir)
+        lockdir_with_prefix <- get_lockdir_with_prefix(lockdir)
+        mk_lockdir(lockdir_with_prefix)
     }
     if (is.na(staged_install)) {
         # environment variable intended as temporary
@@ -2418,7 +2435,8 @@ if(FALSE) {
     for(pkg in allpkgs) {
         if (pkglock) {
             lockdir <- file.path(lib, paste0("00LOCK-", basename(pkg)))
-            mk_lockdir(lockdir)
+            lockdir_with_prefix <- get_lockdir_with_prefix(lockdir)
+            mk_lockdir(lockdir_with_prefix)
         }
         do_install(pkg)
     }