DSL Pretty Print (#91)

* Pretty print in Playground

* feat: enhance formatBridge to merge continuation lines and improve indentation handling

* feat: enhance formatBridge to split adjacent blocks on the same line with a blank line

Author: aarne

packages/bridge-parser/src/bridge-printer.ts

@@ -23,6 +23,10 @@ export {
   serializeBridge,
 } from "./bridge-format.ts";
 
+// ── Formatter ───────────────────────────────────────────────────────────────
+
+export { formatBridge } from "./bridge-printer.ts";
+
 // ── Language service ────────────────────────────────────────────────────────
 
 export { BridgeLanguageService } from "./language-service.ts";

packages/bridge-parser/src/index.ts

@@ -23,7 +23,7 @@ export const WS = createToken({
 export const Comment = createToken({
   name: "Comment",
   pattern: /#[^\r\n]*/,
-  group: Lexer.SKIPPED,
+  group: "comments",
 });
 
 // ── Identifiers (defined first — keywords reference via longer_alt) ────────

packages/bridge-parser/src/parser/lexer.ts

@@ -0,0 +1,179 @@
+import assert from "node:assert/strict";
+import { describe, test } from "node:test";
+import { formatBridge } from "../src/index.ts";
+
+/**
+ * ============================================================================
+ * FULL EXAMPLE TEST CASES
+ *
+ * These tests show complete Bridge DSL snippets with expected formatting.
+ * Edit these to define the canonical style.
+ * ============================================================================
+ */
+
+describe("formatBridge - full examples", () => {
+  test("simple tool declaration", () => {
+    const input = `version 1.5
+tool geo from std.httpCall`;
+    const expected = `version 1.5
+
+tool geo from std.httpCall
+`;
+    assert.equal(formatBridge(input), expected);
+  });
+
+  test("tool with body", () => {
+    const input = `version 1.5
+
+tool geo from std.httpCall{
+.baseUrl="https://example.com"
+.method=GET
+}`;
+    const expected = `version 1.5
+
+tool geo from std.httpCall {
+  .baseUrl = "https://example.com"
+  .method = GET
+}
+`;
+    assert.equal(formatBridge(input), expected);
+  });
+
+  test("bridge block with assignments", () => {
+    const input = `version 1.5
+
+bridge Query.test{
+with input as i
+with output as o
+o.value<-i.value
+}`;
+    const expected = `version 1.5
+
+bridge Query.test {
+  with input as i
+  with output as o
+
+  o.value <- i.value
+}
+`;
+    assert.equal(formatBridge(input), expected);
+  });
+
+  test("define block", () => {
+    const input = `define myHelper{
+with input as i
+o.x<-i.y
+}`;
+    const expected = `define myHelper {
+  with input as i
+
+  o.x <- i.y
+}
+`;
+    assert.equal(formatBridge(input), expected);
+  });
+
+  test("bridge with comment, tool handles, and pipes", () => {
+    const input = `version 1.5
+
+bridge Query.greet {
+#comment
+  with std.str.toUpperCase as uc
+  with std.str.toLowerCase as lc
+  
+  with input as i
+  with output as o
+
+  o.message <- i.name
+  o.upper <- uc: i.name
+  o.lower <- lc: i.name
+}`;
+    const expected = `version 1.5
+
+bridge Query.greet {
+  #comment
+  with std.str.toUpperCase as uc
+  with std.str.toLowerCase as lc
+  with input as i
+  with output as o
+
+  o.message <- i.name
+  o.upper <- uc:i.name
+  o.lower <- lc:i.name
+}
+`;
+    assert.equal(formatBridge(input), expected);
+  });
+
+  test("ternary expressions preserve formatting", () => {
+    const input = `version 1.5
+
+bridge Query.pricing {
+  with input as i
+  with output as o
+
+  # String literal branches
+  o.tier <- i.isPro ? "premium" : "basic"
+
+  # Numeric literal branches
+  o.discount <- i.isPro ? 20 : 5
+
+  # Source ref branches — selects proPrice or basicPrice
+  o.price <- i.isPro ? i.proPrice : i.basicPrice
+}
+`;
+    // Should not change
+    assert.equal(formatBridge(input), input);
+  });
+
+  test("blank line between top-level blocks", () => {
+    const input = `version 1.5
+
+tool geo from std.httpCall
+tool weather from std.httpCall
+bridge Query.a {
+  with input as i
+}
+bridge Query.b {
+  with input as i
+}
+define helper {
+  with input as i
+}`;
+    const expected = `version 1.5
+
+tool geo from std.httpCall
+
+tool weather from std.httpCall
+
+bridge Query.a {
+  with input as i
+}
+
+bridge Query.b {
+  with input as i
+}
+
+define helper {
+  with input as i
+}
+`;
+    assert.equal(formatBridge(input), expected);
+  });
+
+  test("not operator preserves space", () => {
+    const input = `o.requireMFA <- not i.verified
+`;
+    // Should not change
+    assert.equal(formatBridge(input), input);
+  });
+
+  test("blank lines between comments are preserved", () => {
+    const input = `#asdasd
+
+#sdasdsd
+`;
+    // Should not change
+    assert.equal(formatBridge(input), input);
+  });
+});