Support Bash-style default values in EnvVarResolver (#299)

Author: ferenc-csaky

flink-sql-runner/src/main/java/com/datasqrl/flinkrunner/EnvVarResolver.java

@@ -68,11 +68,15 @@ public String resolve(String src) {
       String key;
       String defaultValue = null;
 
-      // Split at first ':' to support default values
-      int colonIdx = rawKey.indexOf(':');
-      if (colonIdx >= 0) {
-        key = rawKey.substring(0, colonIdx);
-        defaultValue = rawKey.substring(colonIdx + 1);
+      // Support bash-style default values: ${VAR:-default} or ${VAR:=default}
+      int splitIdx = rawKey.indexOf(":-");
+      if (splitIdx == -1) {
+        splitIdx = rawKey.indexOf(":=");
+      }
+
+      if (splitIdx >= 0) {
+        key = rawKey.substring(0, splitIdx);
+        defaultValue = rawKey.substring(splitIdx + 2);
       } else {
         key = rawKey;
       }

flink-sql-runner/src/test/java/com/datasqrl/flinkrunner/EnvVarResolverTest.java

@@ -83,16 +83,18 @@ void givenSimilarEnvVariableNames_whenResolveEnv_Vars_thenPartialMatchDoesNotOcc
   @ParameterizedTest
   @CsvSource({
     // Env var not present, fallback used
-    "'${USERNAME:guest}', 'guest'",
-    "'Welcome ${USERNAME:anonymous}', 'Welcome anonymous'",
+    "'${USERNAME:-guest}', 'guest'",
+    "'${USERNAME:=guest}', 'guest'",
+    "'Welcome ${USERNAME:-anonymous}', 'Welcome anonymous'",
     // Env var present, fallback ignored
-    "'${USER:guest}', 'John'",
-    "'Path: ${PATH:/default}', 'Path: /usr/bin'",
+    "'${USER:-guest}', 'John'",
+    "'${USER:=guest}', 'John'",
+    "'Path: ${PATH:-/default}', 'Path: /usr/bin'",
     // Empty default
-    "'Empty fallback: ${MISSING:}', 'Empty fallback: '",
+    "'Empty fallback: ${MISSING:-}', 'Empty fallback: '",
     // Mixed present and fallback
-    "'User=${USER}, ID=${ID:0000}', 'User=John, ID=0000'",
-    "'${MISSING1:default1} and ${MISSING2:default2}', 'default1 and default2'"
+    "'User=${USER}, ID=${ID:-0000}', 'User=John, ID=0000'",
+    "'${MISSING1:-default1} and ${MISSING2:=default2}', 'default1 and default2'"
   })
   void givenDefaultEnvValues_whenResolve_thenFallbackOrUseEnvValue(
       String command, String expected) {
@@ -108,9 +110,10 @@ void givenDefaultEnvValues_whenResolve_thenFallbackOrUseEnvValue(
   @ParameterizedTest
   @ValueSource(
       strings = {
+        "${TOKEN:default}", // Single colon no longer supported
         "${MISSING}", // Still fails because no default
         "Hi ${MISSING}!", // Same
-        "${A:} ${B}" // A has empty default, B is missing
+        "${A:-} ${B}" // A has empty default, B is missing
       })
   void givenMissingEnvWithoutDefault_whenResolve_thenThrowException(String command) {
     Map<String, String> envVariables = Map.of("A", "something");
@@ -122,9 +125,11 @@ void givenMissingEnvWithoutDefault_whenResolve_thenThrowException(String command
 
   @ParameterizedTest
   @CsvSource({
-    "'${TOKEN:abc:def}', 'abc:def'", // Semicolon inside fallback value
-    "'${TOKEN:abc:def:ghi}', 'abc:def:ghi'", // colon is only split on first occurrence
-    "'${TOKEN:}', ''" // colon at the end
+    "'${TOKEN:-abc:def}', 'abc:def'", // Bash-style with colon in fallback
+    "'${TOKEN:=abc:def}', 'abc:def'", // Bash-style with colon in fallback
+    "'${TOKEN:-abc:def:ghi}', 'abc:def:ghi'", // Bash-style
+    "'${TOKEN:-}', ''", // Bash-style colon-dash at the end
+    "'${TOKEN:=}', ''" // Bash-style colon-equals at the end
   })
   void givenFallbackWithColons_whenResolve_thenParseCorrectly(String command, String expected) {
     Map<String, String> envVariables = Map.of(); // No TOKEN set