Raise proper error message if duplicate macros found

CHANGELOG.md

@@ -8,6 +8,7 @@
 - Moving from 'master' to 'HEAD' default branch in git ([#3057](https://github.com/fishtown-analytics/dbt/issues/3057), [#3104](https://github.com/fishtown-analytics/dbt/issues/3104), [#3117](https://github.com/fishtown-analytics/dbt/issues/3117)))
 - Requirement on `dataclasses` is relaxed to be between `>=0.6,<0.9` allowing dbt to cohabit with other libraries which required higher versions. ([#3150](https://github.com/fishtown-analytics/dbt/issues/3150), [#3151](https://github.com/fishtown-analytics/dbt/pull/3151))
 - Add feature to add `_n` alias to same column names in SQL query ([#3147](https://github.com/fishtown-analytics/dbt/issues/3147), [#3158](https://github.com/fishtown-analytics/dbt/pull/3158))
+- Raise a proper error message if dbt parses a macro twice due to macro duplication or misconfiguration. ([#2449](https://github.com/fishtown-analytics/dbt/issues/2449), [#3165](https://github.com/fishtown-analytics/dbt/pull/3165))
 
 ### Features
 - Add optional configs for `require_partition_filter` and `partition_expiration_days` in BigQuery ([#1843](https://github.com/fishtown-analytics/dbt/issues/1843), [#2928](https://github.com/fishtown-analytics/dbt/pull/2928))
@@ -27,6 +28,7 @@ Contributors:
 - [@VasiliiSurov](https://github.com/VasiliiSurov) ([#3104](https://github.com/fishtown-analytics/dbt/pull/3104))
 - [@bastienboutonnet](https://github.com/bastienboutonnet) ([#3151](https://github.com/fishtown-analytics/dbt/pull/3151))
 - [@techytushar](https://github.com/techytushar) ([#3158](https://github.com/fishtown-analytics/dbt/pull/3158))
+- [@cgopalan](https://github.com/cgopalan) ([#3165](https://github.com/fishtown-analytics/dbt/pull/3165))
 
 ## dbt 0.19.1 (Release TBD)
 

core/dbt/parser/results.py

@@ -125,7 +125,7 @@ def add_macro(self, source_file: SourceFile, macro: ParsedMacro):
             # subtract 2 for the "Compilation Error" indent
             # note that the line wrap eats newlines, so if you want newlines,
             # this is the result :(
-            msg = line_wrap_message(
+            dup_macro_msg = line_wrap_message(
                 f'''\
                 dbt found two macros named "{macro.name}" in the project
                 "{macro.package_name}".
@@ -140,6 +140,25 @@ def add_macro(self, source_file: SourceFile, macro: ParsedMacro):
                 ''',
                 subtract=2
             )
+            dup_path_msg = line_wrap_message(
+                f"""\
+                The macro {macro.name} in file {macro.original_file_path}
+                was parsed multiple times by dbt. This error happens when a
+                macro is defined multiple times in the same file, or when a
+                path is duplicated in a dbt_project.yml configuration.
+                To fix this error, check:
+
+                    - {macro.original_file_path}
+
+                    - The `macro-paths` configurations in dbt_project.yml
+                """,
+                subtract=2,
+            )
+            msg = (
+                dup_path_msg
+                if macro.original_file_path == other_path
+                else dup_macro_msg
+            )
             raise_compiler_error(msg)
 
         self.macros[macro.unique_id] = macro