在targets流水线中使用terra加载栅格数据遇外部指针无效错误

尝试在targets流水线中使用terra包加载栅格数据，对应的_targets.R文件代码如下：

# Created by use_targets().
# Follow the comments below to fill in this target script.
# Then follow the manual to check and run the pipeline:
#   https://books.ropensci.org/targets/walkthrough.html#inspect-the-pipeline # nolint

# Load packages required to define the pipeline:
library(targets)
# library(tarchetypes) # Load other packages as needed. # nolint

# Set target options:
tar_option_set(
  packages = c(
    "tidyverse",
    "terra",
  ), # packages that your targets need to run
  format = "rds" # default storage format
  # Set other options as needed.
)

# tar_make_clustermq() configuration (okay to leave alone):
options(
  clustermq.scheduler = "multiprocess"
)

# tar_make_future() configuration (okay to leave alone):
# Install packages {{future}}, {{future.callr}}, and {{future.batchtools}} to allow use_targets() to configure tar_make_future() options.

# Run the R scripts in the R/ folder with your custom functions:
tar_source()
# source("other_functions.R") # Source other scripts as needed. # nolint

# Replace the target list below with your own:
list(
  ## Load all data in R/load_data.R
  tar_target(esg_rast_file, "data/ESGs/ESGs.tif", format="file"),
  tar_target(esg_rast_data, terra::rast(esg_rast_file))
)

运行tar_make()后的输出如下：

r$> library(targets)

r$> tar_make()
• start target esg_rast_file
• built target esg_rast_file [6.42 seconds]
• start target esg_rast_data
• built target esg_rast_data [0.05 seconds]
• end pipeline [7.96 seconds]
 
r$> tar_load(esg_rast_data)
NULL value passed as symbol address
r$> esg_rast_data
class       : SpatRaster
Error in x@ptr$nrow() : external pointer is not valid

这是正常现象吗？是否存在操作错误？同时加载sf的.shp数据也遇到了类似问题，似乎遗漏了关键步骤。

• 问题核心：terra的SpatRaster和sf的空间对象依赖外部指针，默认的rds格式无法正确序列化/反序列化这类对象，导致加载后指针失效。
• 修正步骤：
  1. 对于terra栅格数据：将目标的存储格式改为"terra"，这是targets专为SpatRaster设计的格式，能正确处理外部指针。
  2. 对于sf矢量数据：同理，将目标格式改为"sf"。
• 修改后的_targets.R关键部分：

list(
  tar_target(esg_rast_file, "data/ESGs/ESGs.tif", format="file"),
  # 为terra栅格指定format="terra"
  tar_target(esg_rast_data, terra::rast(esg_rast_file), format="terra")
)

• 补充说明：
  • 若流水线中多数是同类型空间对象，也可以在tar_option_set()中全局设置格式，比如tar_option_set(format = "terra")。
  • 重新运行tar_make()后，再用tar_load(esg_rast_data)即可正常加载和使用栅格对象。

内容的提问来源于stack exchange，提问作者Mike Schmidt