Add the ability for errors messages to link to error explanations

packages/malloy/src/lang/ast/expressions/expr-func.ts

@@ -350,9 +350,9 @@ export class ExprFunc extends ExpressionDef {
               ? `'.' paths are not yet supported in sql interpolations, found ${unsupportedInterpolations.at(
                   0
                 )}`
-              : `'.' paths are not yet supported in sql interpolations, found [${unsupportedInterpolations.join(
+              : `'.' paths are not yet supported in sql interpolations, found (${unsupportedInterpolations.join(
                   ', '
-                )}]`;
+                )})`;
           this.log(unsupportedInterpolationMsg);
 
           return errorFor(

packages/malloy/src/lang/ast/expressions/pick-when.ts

@@ -100,7 +100,9 @@ export class Pick extends ExpressionDef {
       );
       if (returnType && !FT.typeEq(returnType, thenExpr, true)) {
         const whenType = FT.inspect(thenExpr);
-        this.log(`pick type '${whenType}', expected '${returnType.dataType}'`);
+        this.log(
+          `pick type '${whenType}', expected '${returnType.dataType}'[pick-values-must-match]`
+        );
         return errorFor('pick when type');
       }
       returnType = typeCoalesce(returnType, thenExpr);
@@ -114,7 +116,7 @@ export class Pick extends ExpressionDef {
       this.log(
         `${errSrc} type '${FT.inspect(elseVal)}', expected '${
           returnType.dataType
-        }'`
+        }'[pick-values-must-match]`
       );
       return errorFor('pick else type');
     }
@@ -164,7 +166,9 @@ export class Pick extends ExpressionDef {
       }
       if (returnType && !FT.typeEq(returnType, aChoice.pick, true)) {
         const whenType = FT.inspect(aChoice.pick);
-        this.log(`pick type '${whenType}', expected '${returnType.dataType}'`);
+        this.log(
+          `pick type '${whenType}', expected '${returnType.dataType}'[pick-values-must-match]`
+        );
         return errorFor('pick value type');
       }
       returnType = typeCoalesce(returnType, aChoice.pick);
@@ -196,7 +200,9 @@ export class Pick extends ExpressionDef {
     returnType = typeCoalesce(returnType, defVal);
     if (!FT.typeEq(returnType, defVal, true)) {
       this.elsePick.log(
-        `else type '${FT.inspect(defVal)}', expected '${returnType.dataType}'`
+        `else type '${FT.inspect(defVal)}', expected '${
+          returnType.dataType
+        }'[pick-values-must-match]`
       );
       return errorFor('pick value type mismatch');
     }

packages/malloy/src/lang/parse-log.ts

@@ -32,6 +32,7 @@ export interface LogMessage {
   message: string;
   at?: DocumentLocation;
   severity: LogSeverity;
+  errorTag?: string;
 }
 
 export interface MessageLogger {
@@ -50,7 +51,23 @@ export class MessageLog implements MessageLogger {
     return this.rawLog;
   }
 
+  /**
+   * Add a message to the log.
+   *
+   * If the messsage ends with '[tag]', the tag is removed and stored in the `errorTag` field.
+   * @param logMsg Message possibly containing an error tag
+   */
   log(logMsg: LogMessage): void {
+    const msg = logMsg.message;
+    // github security is worried about msg.match(/^(.+)\[(.+)\]$/ because if someone
+    // could craft code with a long varibale name which would blow up that regular expression
+    if (msg.endsWith(']')) {
+      const tagStart = msg.lastIndexOf('[');
+      if (tagStart > 0) {
+        logMsg.message = msg.slice(0, tagStart);
+        logMsg.errorTag = msg.slice(tagStart + 1, -1);
+      }
+    }
     this.rawLog.push(logMsg);
   }
 

packages/malloy/src/lang/test/parse.spec.ts

@@ -1026,3 +1026,10 @@ describe('sql_functions', () => {
 
 test('non breaking space in source', () =>
   expect('source:\u00a0z\u00a0is\u00a0a').toParse());
+
+test('error tagging', () => {
+  const m = model`run: a -> { select: err is pick 1 when true else 'one' }`;
+  expect(m).translationToFailWith("else type 'string', expected 'number'");
+  const firstErr = m.translator.root.logger.getLog()[0];
+  expect(firstErr?.errorTag).toBe('pick-values-must-match');
+});

test/src/databases/all/expr.spec.ts

@@ -596,7 +596,7 @@ describe.each(runtimes.runtimeList)('%s', (databaseName, runtime) => {
           `
         );
         await expect(query.run()).rejects.toThrow(
-          "'.' paths are not yet supported in sql interpolations, found [${a.seats}, ${a.seats}, ${a.total_seats}]"
+          "'.' paths are not yet supported in sql interpolations, found (${a.seats}, ${a.seats}, ${a.total_seats})"
         );
       });