Add --env-file default for env (bash parsed).

In addition to bash, the wrapper script requires sort and comm commands
to be installed and on the PATH.

If the --env-file option is used then a bash wrapper is invoked to
source the file that tracks the before and after of variables and this
is used to construct the resulting environment map. This is done by
making all variable settings implicitly exports (`set -a`) and then
printing the before and after variables using `declare -x`, and finally
getting added ones using `comm -13`.

src/dctest/core.cljs

@@ -37,6 +37,9 @@ Options:
   --results-file RESULTS-FILE   Write JSON results to RESULTS-FILE
   --schema-file SCHEMA          Path to input schema file [env: DCTEST_SCHEMA]
                                 [default: ./schemas/input.yaml]
+  --env-file FILE               Load an FILE an default env settings.
+                                WARNING: FILE is sourced/run by bash.
+                                         DO NOT WITH UNSANITIZED FILES.
 ")
 
 (set! *warn-on-infer* false)
@@ -538,12 +541,14 @@ Options:
 (defn -main [& argv]
   (P/let [opts (parse-opts usage (or argv #js []))
           {:keys [continue-on-error project test-suite test-filter
-                  quiet verbose-commands]} opts
+                  quiet verbose-commands env-file]} opts
           _ (when (empty? test-suite)
               (Eprintln (str "WARNING: no test-suite was specified")))
 
+          default-env (when env-file (util/load-env env-file))
           context {:docker (Docker.)
-                   :env {"COMPOSE_PROJECT_NAME" project}
+                   :env (merge {"COMPOSE_PROJECT_NAME" project}
+                               default-env)
                    :process (js-process)
                    :start (js/Date.now)
                    :opts {:project project

src/dctest/util.cljs

@@ -8,7 +8,7 @@
     [clojure.pprint :refer [pprint print-table]]
     [dctest.expressions :as expr]
     [promesa.core :as P]
-    [viasat.util :refer [Eprintln fatal read-file]]
+    [viasat.util :refer [Eprintln fatal read-file exec-promise]]
     ["js-yaml" :as yaml]
     #_["ajv$default" :as Ajv]
     ))
@@ -61,6 +61,20 @@
         (Eprintln "Failure to load file:" path)
         (fatal 2 (.-message err))))))
 
+(defn load-env [path]
+  "Source path (using bash) and return a map of modified env variables.
+  Requires bash, sort, and comm on the PATH."
+  [path]
+  (let [bash-cmd (str "bash -c '_AAAAA=$(declare -x | sort);"
+                      "set -a; source \"" path "\";"
+                      "_ZZZZZ=$(declare -x | sort);"
+                      "comm -13 <(echo \"${_AAAAA}\") <(echo \"${_ZZZZZ}\")"
+                      "  | sed \"s/^declare -x //\"'")]
+    (P/let [result (exec-promise bash-cmd)]
+      (->> (S/split-lines (.-stdout result))
+           (map #(first (re-seq #"([^=]*)=\"(.*)\"" %)))
+           (reduce (fn [m [_ k v]] (assoc m k v)) {})))))
+
 (defn ajv-error-to-str [error]
   (let [path (:instancePath error)
         params (dissoc (:params error) :type :pattern :missingProperty)]