[smart pipes] Add support for question-mark tokens

packages/babel-parser/src/parser/expression.js

@@ -983,29 +983,11 @@ export default class ExpressionParser extends LValParser {
       }
 
       case tt.hash: {
-        if (this.state.inPipeline) {
-          node = this.startNode();
-
-          if (
-            this.getPluginOption("pipelineOperator", "proposal") !== "smart"
-          ) {
-            this.raise(
-              node.start,
-              "Primary Topic Reference found but pipelineOperator not passed 'smart' for 'proposal' option.",
-            );
-          }
+        return this.parsePrimaryTopicReference("#");
+      }
 
-          this.next();
-          if (this.primaryTopicReferenceIsAllowedInCurrentTopicContext()) {
-            this.registerTopicReference();
-            return this.finishNode(node, "PipelinePrimaryTopicReference");
-          } else {
-            throw this.raise(
-              node.start,
-              `Topic reference was used in a lexical context without topic binding`,
-            );
-          }
-        }
+      case tt.question: {
+        return this.parsePrimaryTopicReference("?");
       }
 
       default:
@@ -2110,6 +2092,82 @@ export default class ExpressionParser extends LValParser {
     return this.finishNode(node, "YieldExpression");
   }
 
+  // Parses a smart-pipeline primary topic reference.
+  // The pipelineOperator plugin must be active, and its proposal option must be "smart".
+  // The topicToken argument is "#" or "?" and is matched against the topicToken option
+  // given to the pipelineOperator plugin's topicToken option (which is "#" by default).
+
+  parsePrimaryTopicReference(
+    topicToken: N.PipelineProposedTopicToken,
+  ): N.PipelinePrimaryTopicReference {
+    if (this.state.inPipeline) {
+      const node = this.startNode();
+
+      if (this.getPluginOption("pipelineOperator", "proposal") !== "smart") {
+        this.raise(
+          node.start,
+          "Topic reference found but pipelineOperator plugin was not passed 'smart' " +
+            "for 'proposal' option.",
+        );
+      }
+
+      this.validateTopicToken(topicToken);
+      this.next();
+
+      if (this.primaryTopicReferenceIsAllowedInCurrentTopicContext()) {
+        this.registerTopicReference();
+        return this.finishNode(node, "PipelinePrimaryTopicReference");
+      } else {
+        throw this.raise(
+          node.start,
+          `Topic reference was used in a lexical context without topic binding`,
+        );
+      }
+    } else {
+      throw this.unexpected();
+    }
+  }
+
+  // Asserts that the given topic token is valid under the pipelineOperator plugin's
+  // topicToken configuration option.
+
+  validateTopicToken(topicToken: N.PipelineProposedTopicToken): void {
+    if (!this.matchesTopicTokenConfiguration(topicToken)) {
+      const node = this.startNode();
+      const topicTokenOption = this.getPipelineOperatorPluginTopicTokenOption();
+      const message = topicTokenOption
+        ? `Pipeline was used with ${topicToken} topic token, but ` +
+          `pipelineOperator plugin was passed a "topicToken": ` +
+          `"${topicTokenOption}" option`
+        : `Pipeline was used with ${topicToken} topic token, but ` +
+          `pipelineOperator plugin was not passed a "topicToken" option, which ` +
+          `is "#" by default`;
+      this.raise(node.start, message);
+    }
+  }
+
+  // Tests whether a topic-token string is the same as the pipelineOperator plugin's
+  // topicToken configuration option.
+
+  matchesTopicTokenConfiguration(
+    topicToken: N.PipelineProposedTopicToken,
+  ): boolean {
+    const defaultTopicToken = "#";
+    const pluginConfigurationTopicToken = this.getPluginOption(
+      "pipelineOperator",
+      "topicToken",
+    );
+    const effectivePluginConfigurationTopicToken =
+      pluginConfigurationTopicToken || defaultTopicToken;
+    return effectivePluginConfigurationTopicToken === topicToken;
+  }
+
+  // Returns the value of the pipelineOperator plugin's topicToken configuration option.
+
+  getPipelineOperatorPluginTopicTokenOption(): ?string {
+    return this.getPluginOption("pipelineOperator", "topicToken");
+  }
+
   // Validates a pipeline (for any of the pipeline Babylon plugins) at the point
   // of the infix operator `|>`.
 
@@ -2191,7 +2249,7 @@ export default class ExpressionParser extends LValParser {
         if (!this.topicReferenceWasUsedInCurrentTopicContext()) {
           throw this.raise(
             startPos,
-            `Pipeline is in topic style but does not use topic reference`,
+            `Pipeline is in topic style but does not use any topic reference`,
           );
         }
         bodyNode.expression = childExpression;
@@ -2269,8 +2327,8 @@ export default class ExpressionParser extends LValParser {
     }
   }
 
-  // Register the use of a primary topic reference (`#`) within the current
-  // topic context.
+  // For the smart-pipelines plugin.
+  // Register the use of a primary topic reference within the current topic context.
   registerTopicReference(): void {
     this.state.topicContext.maxTopicIndex = 0;
   }

packages/babel-parser/src/tokenizer/index.js

@@ -375,7 +375,7 @@ export default class Tokenizer extends LocationParser {
   //
   // All in the name of speed.
 
-  // number sign is "#"
+  // Number sign is "#", aka the hash sign.
   readToken_numberSign(): void {
     if (this.state.pos === 0 && this.readToken_interpreter()) {
       return;

packages/babel-parser/src/types.js

@@ -598,6 +598,12 @@ export type PipelineStyle =
   | "PipelineBareAwaitedFunction"
   | "PipelineTopicExpression";
 
+export type PipelinePrimaryTopicReference = NodeBase & {
+  type: "PipelinePrimaryTopicReference",
+};
+
+export type PipelineProposedTopicToken = "#" | "?";
+
 // Template Literals
 
 export type TemplateLiteral = NodeBase & {

packages/babel-parser/test/fixtures/experimental/pipeline-operator/proposal-smart,-default-token,-error,-invalid-topic-token,-question-mark/input.js

@@ -0,0 +1 @@
+x |> ?;

packages/babel-parser/test/fixtures/experimental/pipeline-operator/proposal-smart,-default-token,-error,-invalid-topic-token,-question-mark/options.json

@@ -0,0 +1,4 @@
+{
+  "plugins": [["pipelineOperator", { "proposal": "smart" }]],
+  "throws": "Pipeline was used with ? topic token, but pipelineOperator plugin was not passed a \"topicToken\" option, which is \"#\" by default (1:5)"
+}

packages/babel-parser/test/fixtures/experimental/pipeline-operator/proposal-smart,-default-token,-error,-nested-pipelines,-topic-style-with-arrow-function-with-bare-style,-no-outer-topic-reference/options.json

@@ -0,0 +1,4 @@
+{
+  "plugins": [["pipelineOperator", { "proposal": "smart" }]],
+  "throws": "Pipeline is in topic style but does not use any topic reference (1:5)"
+}

packages/babel-parser/test/fixtures/experimental/pipeline-operator/proposal-smart,-default-token,-error,-nested-pipelines,-topic-style-with-arrow-function-with-topic-style,-no-inner-topic-reference/options.json

@@ -0,0 +1,4 @@
+{
+  "plugins": [["pipelineOperator", { "proposal": "smart" }]],
+  "throws": "Pipeline is in topic style but does not use any topic reference (1:16)"
+}

packages/babel-parser/test/fixtures/experimental/pipeline-operator/proposal-smart,-default-token,-error,-nested-pipelines,-topic-style-with-arrow-function-with-topic-style,-no-outer-topic-reference/options.json

@@ -0,0 +1,4 @@
+{
+  "plugins": [["pipelineOperator", { "proposal": "smart" }]],
+  "throws": "Pipeline is in topic style but does not use any topic reference (1:5)"
+}

packages/babel-parser/test/fixtures/experimental/pipeline-operator/proposal-smart,-default-token,-error,-nested-pipelines,-topic-style-with-inner-topic-style,-no-inner-topic-reference/options.json

@@ -0,0 +1,4 @@
+{
+  "plugins": [["pipelineOperator", { "proposal": "smart" }]],
+  "throws": "Pipeline is in topic style but does not use any topic reference (1:11)"
+}

packages/babel-parser/test/fixtures/experimental/pipeline-operator/proposal-smart,-default-token,-error,-nested-pipelines,-topic-style-with-inner-topic-style,-no-outer-topic-reference/options.json

@@ -0,0 +1,4 @@
+{
+  "plugins": [["pipelineOperator", { "proposal": "smart" }]],
+  "throws": "Pipeline is in topic style but does not use any topic reference (1:5)"
+}

packages/babel-parser/test/fixtures/experimental/pipeline-operator/proposal-smart,-default-token,-error,-topic-style,-computed,-no-topic-reference/options.json

@@ -0,0 +1,4 @@
+{
+  "plugins": [["pipelineOperator", { "proposal": "smart" }]],
+  "throws": "Pipeline is in topic style but does not use any topic reference (1:9)"
+}

packages/babel-parser/test/fixtures/experimental/pipeline-operator/proposal-smart,-default-token,-error,-topic-style,-no-topic-reference,-addition/options.json

@@ -0,0 +1,4 @@
+{
+  "plugins": [["pipelineOperator", { "proposal": "smart" }]],
+  "throws": "Pipeline is in topic style but does not use any topic reference (1:9)"
+}

packages/babel-parser/test/fixtures/experimental/pipeline-operator/proposal-smart,-default-token,-error,-topic-style,-no-topic-reference,-class-expression/options.json

@@ -0,0 +1,4 @@
+{
+  "plugins": [["pipelineOperator", { "proposal": "smart" }]],
+  "throws": "Pipeline is in topic style but does not use any topic reference (1:9)"
+}

packages/babel-parser/test/fixtures/experimental/pipeline-operator/proposal-smart,-default-token,-error,-topic-style,-no-topic-reference,-function-expression/options.json

@@ -0,0 +1,4 @@
+{
+  "plugins": [["pipelineOperator", { "proposal": "smart" }]],
+  "throws": "Pipeline is in topic style but does not use any topic reference (1:9)"
+}

packages/babel-parser/test/fixtures/experimental/pipeline-operator/proposal-smart,-question-mark,-bare-style,-function-calls,-chained,-multiline/input.js

@@ -0,0 +1,4 @@
+let result = "hello"
+|> doubleSay
+|> text.capitalize
+|> a.b.exclaim;

packages/babel-parser/test/fixtures/experimental/pipeline-operator/proposal-smart,-question-mark,-bare-style,-function-calls,-chained,-multiline/options.json

@@ -0,0 +1,3 @@
+{
+  "plugins": [["pipelineOperator", { "proposal": "smart", "topicToken": "?" }]]
+}