fix(snippets): trim leading whitespace when extracting snippets (#449)

* fix(snippets): trim leading whitespace when extracting snippets

* docs: add docstring for _trim_leading_whitespace

synthtool/gcp/snippets.py

@@ -21,6 +21,35 @@
 CLOSE_SNIPPET_REGEX = r".*\[END ([a-z0-9_]+)\].*$"
 
 
+def _trim_leading_whitespace(lines: List[str]) -> List[str]:
+    """Trims leading, plain spaces from the snippet content. Finds the minimum
+    number of leading spaces, ignoring empty lines, and removes that number of
+    spaces from each line.
+
+    Args:
+        lines (List[str]): Lines of content. These lines are newline terminated.
+
+    Returns:
+        List of trimmed lines.
+    """
+
+    def number_of_leading_spaces(input: str) -> int:
+        return len(input) - len(input.lstrip(" "))
+
+    def is_empty_line(input: str) -> bool:
+        if re.match(r"^\s*$", input):
+            return True
+        return False
+
+    leading_spaces = [
+        number_of_leading_spaces(line) for line in lines if not is_empty_line(line)
+    ]
+    max_leading_spaces = min(leading_spaces)
+    return [
+        "\n" if is_empty_line(line) else line[max_leading_spaces:] for line in lines
+    ]
+
+
 def all_snippets_from_file(sample_file: str) -> Dict[str, str]:
     """Reads in a sample file and parse out all contained snippets.
 
@@ -56,7 +85,10 @@ def all_snippets_from_file(sample_file: str) -> Dict[str, str]:
                 for snippet in open_snippets:
                     snippet_lines[snippet].append(line)
 
-    return {snippet: "".join(lines) for snippet, lines in snippet_lines.items()}
+    return {
+        snippet: "".join(_trim_leading_whitespace(lines))
+        for snippet, lines in snippet_lines.items()
+    }
 
 
 def all_snippets(snippet_globs: List[str]) -> Dict[str, str]:

tests/test_snippets.py

@@ -37,24 +37,24 @@ def test_load_snippets():
     )
     assert (
         all_snippets["monitoring_install_with_bom"]
-        == """  <dependencyManagement>
-    <dependencies>
-      <dependency>
-        <groupId>com.google.cloud</groupId>
-        <artifactId>libraries-bom</artifactId>
-        <version>3.5.0</version>
-        <type>pom</type>
-        <scope>import</scope>
-      </dependency>
-    </dependencies>
-  </dependencyManagement>
-
+        == """<dependencyManagement>
   <dependencies>
     <dependency>
       <groupId>com.google.cloud</groupId>
-      <artifactId>google-cloud-monitoring</artifactId>
+      <artifactId>libraries-bom</artifactId>
+      <version>3.5.0</version>
+      <type>pom</type>
+      <scope>import</scope>
     </dependency>
   </dependencies>
+</dependencyManagement>
+
+<dependencies>
+  <dependency>
+    <groupId>com.google.cloud</groupId>
+    <artifactId>google-cloud-monitoring</artifactId>
+  </dependency>
+</dependencies>
 """
     )