fix Generate Flutter Rust bridge

.gitea/workflows/android.yml

@@ -706,25 +706,23 @@ jobs:
 
               return "\n".join(body) + "\n"
 
-          replacements = {
-              "${{ env.CARGO_EXPAND_VERSION }}":
-                  "${CARGO_EXPAND_VERSION}",
+          def replace_expression(body, expression, replacement):
+              # Match GitHub/Gitea expression syntax without placing a literal
+              # "${{ ... }}" token inside this workflow. Otherwise Gitea
+              # expands it before this Python code runs.
+              pattern = (
+                  r"\$\{\{\s*"
+                  + re.escape(expression)
+                  + r"\s*\}\}"
+              )
 
-              "${{env.CARGO_EXPAND_VERSION}}":
-                  "${CARGO_EXPAND_VERSION}",
+              body, count = re.subn(
+                  pattern,
+                  lambda _match: replacement,
+                  body,
+              )
 
-              "${{ env.FLUTTER_RUST_BRIDGE_VERSION }}":
-                  "${FLUTTER_RUST_BRIDGE_VERSION}",
-
-              "${{env.FLUTTER_RUST_BRIDGE_VERSION}}":
-                  "${FLUTTER_RUST_BRIDGE_VERSION}",
-
-              "${{ matrix.job.flutter-version }}":
-                  "${BRIDGE_FLUTTER_VERSION}",
-
-              "${{matrix.job.flutter-version}}":
-                  "${BRIDGE_FLUTTER_VERSION}",
-          }
+              return body, count
 
           for filename, step in (
               ("bridge-prepare.sh", "Install flutter rust bridge deps"),
@@ -732,8 +730,50 @@ jobs:
           ):
               body = extract_run(step)
 
-              for old, new in replacements.items():
-                  body = body.replace(old, new)
+              body, cargo_expand_count = replace_expression(
+                  body,
+                  "env.CARGO_EXPAND_VERSION",
+                  "${CARGO_EXPAND_VERSION}",
+              )
+
+              body, frb_count = replace_expression(
+                  body,
+                  "env.FLUTTER_RUST_BRIDGE_VERSION",
+                  "${FLUTTER_RUST_BRIDGE_VERSION}",
+              )
+
+              body, flutter_version_count = replace_expression(
+                  body,
+                  "matrix.job.flutter-version",
+                  "${BRIDGE_FLUTTER_VERSION}",
+              )
+
+              if step == "Install flutter rust bridge deps":
+                  if cargo_expand_count < 1:
+                      raise SystemExit(
+                          "Upstream bridge step no longer references "
+                          "CARGO_EXPAND_VERSION"
+                      )
+
+                  if frb_count < 1:
+                      raise SystemExit(
+                          "Upstream bridge step no longer references "
+                          "FLUTTER_RUST_BRIDGE_VERSION"
+                      )
+
+                  if flutter_version_count < 1:
+                      raise SystemExit(
+                          "Upstream bridge step no longer references "
+                          "matrix.job.flutter-version"
+                      )
+
+              # Fail explicitly if upstream introduces another expression in
+              # these run blocks that we do not yet translate.
+              if re.search(r"\$\{\{", body):
+                  raise SystemExit(
+                      f"Unresolved GitHub expression remains in {step}:\\n"
+                      + body
+                  )
 
               script = Path(filename)
 
@@ -749,6 +789,16 @@ jobs:
               print(f"Generated {filename} from upstream {step!r}")
           PY
 
+          echo "===== bridge-prepare.sh ====="
+          cat bridge-prepare.sh
+
+          echo
+          echo "===== bridge-generate.sh ====="
+          cat bridge-generate.sh
+
+          bash -n bridge-prepare.sh
+          bash -n bridge-generate.sh
+
           ./bridge-prepare.sh
           ./bridge-generate.sh