stdlib: add env_vars_required (#872)

Check presence of env vars:

    env_vars_required SOME_TOKEN

Fixes #843

man/direnv-stdlib.1

@@ -126,6 +126,27 @@ source_env_if_exists .envrc.private
 .fi
 .RE
 
+.SS \fB\fCenv_vars_required <varname> [<varname> ...]\fR
+.PP
+Logs error for every variable not present in the environment or having an empty value.
+.br
+Typically this is used in combination with source_env and source_env_if_exists.
+
+.PP
+Example:
+
+.PP
+.RS
+
+.nf
+# expect .envrc.private to provide tokens
+source_env .envrc.private
+# check presence of tokens
+env_vars_required GITHUB_TOKEN OTHER_TOKEN
+
+.fi
+.RE
+
 .SS \fB\fCsource_up [<filename>]\fR
 .PP
 Loads another \fB\fC\&.envrc\fR if found when searching from the parent directory up to /.

man/direnv-stdlib.1.md

@@ -90,6 +90,19 @@ Example:
 
     source_env_if_exists .envrc.private
 
+### `env_vars_required <varname> [<varname> ...]`
+
+Logs error for every variable not present in the environment or having an empty value.  
+Typically this is used in combination with source_env and source_env_if_exists.
+
+Example:
+
+    # expect .envrc.private to provide tokens
+    source_env .envrc.private
+    # check presence of tokens
+    env_vars_required GITHUB_TOKEN OTHER_TOKEN
+
+
 ### `source_up [<filename>]`
 
 Loads another `.envrc` if found when searching from the parent directory up to /.

stdlib.sh

@@ -372,6 +372,33 @@ source_env_if_exists() {
   if [[ -f "$1" ]]; then source_env "$1"; fi
 }
 
+# Usage: env_vars_required <varname> [<varname> ...]
+#
+# Logs error for every variable not present in the environment or having an empty value.  
+# Typically this is used in combination with source_env and source_env_if_exists.
+#
+# Example:
+#
+#     # expect .envrc.private to provide tokens
+#     source_env .envrc.private
+#     # check presence of tokens
+#     env_vars_required GITHUB_TOKEN OTHER_TOKEN
+#
+env_vars_required() {
+  local environment
+  local -i ret
+  environment=$(env)
+  ret=0
+
+  for var in "$@"; do
+    if [[ "$environment" != *"$var="* || -z ${!var:-}  ]]; then
+      log_error "env var $var is required but missing/empty"
+      ret=1
+    fi
+  done
+  return "$ret"
+}
+
 # Usage: watch_file <filename> [<filename> ...]
 #
 # Adds each <filename> to the list of files that direnv will watch for changes -

test/stdlib.bash

@@ -192,6 +192,26 @@ test_name source_env_if_exists
   [[ $FOO = bar ]]
 )
 
+test_name env_vars_required
+(
+  load_stdlib
+
+  export FOO=1
+  env_vars_required FOO
+
+  # these should all fail
+  # shellcheck disable=SC2034
+  BAR=1
+  export BAZ=
+  output="$(env_vars_required BAR BAZ MISSING 2>&1 > /dev/null || echo "--- result: $?")"
+
+  [[ "${output#*'--- result: 1'}" != "$output" ]]
+  [[ "${output#*'BAR is required'}" != "$output" ]]
+  [[ "${output#*'BAZ is required'}" != "$output" ]]
+  [[ "${output#*'MISSING is required'}" != "$output" ]]
+)
+
+
 # test strict_env and unstrict_env
 ./strict_env_test.bash