Always return a str from literal_name (#978)

CHANGELOG.md

@@ -12,6 +12,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 ### Fixed
 
 - `TypeError` when PDF object reference cannot be parsed as int ([#972](https://github.com/pdfminer/pdfminer.six/pull/972))])
+- `TypeError` when PDF literal cannot be converted to str ([#978](https://github.com/pdfminer/pdfminer.six/pull/978))
 
 ### Removed
 

pdfminer/pdfinterp.py

@@ -947,7 +947,7 @@ def do_EI(self, obj: PDFStackT) -> None:
 
     def do_Do(self, xobjid_arg: PDFStackT) -> None:
         """Invoke named XObject"""
-        xobjid = cast(str, literal_name(xobjid_arg))
+        xobjid = literal_name(xobjid_arg)
         try:
             xobj = stream_value(self.xobjmap[xobjid])
         except KeyError:

pdfminer/psparser.py

@@ -117,23 +117,21 @@ def intern(self, name: PSLiteral.NameType) -> _SymbolT:
 KEYWORD_DICT_END = KWD(b">>")
 
 
-def literal_name(x: object) -> Any:
-    if not isinstance(x, PSLiteral):
+def literal_name(x: Any) -> str:
+    if isinstance(x, PSLiteral):
+        if isinstance(x.name, str):
+            return x.name
+        try:
+            return str(x.name, "utf-8")
+        except UnicodeDecodeError:
+            return str(x.name)
+    else:
         if settings.STRICT:
             raise PSTypeError(f"Literal required: {x!r}")
-        else:
-            name = x
-    else:
-        name = x.name
-        if not isinstance(name, str):
-            try:
-                name = str(name, "utf-8")
-            except Exception:
-                pass
-    return name
+        return str(x)
 
 
-def keyword_name(x: object) -> Any:
+def keyword_name(x: Any) -> Any:
     if not isinstance(x, PSKeyword):
         if settings.STRICT:
             raise PSTypeError("Keyword required: %r" % x)
@@ -523,12 +521,13 @@ def nexttoken(self) -> Tuple[int, PSBaseParserToken]:
 
 
 # Stack slots may by occupied by any of:
+#  * the name of a literal
 #  * the PSBaseParserToken types
 #  * list (via KEYWORD_ARRAY)
 #  * dict (via KEYWORD_DICT)
 #  * subclass-specific extensions (e.g. PDFStream, PDFObjRef) via ExtraT
 ExtraT = TypeVar("ExtraT")
-PSStackType = Union[float, bool, PSLiteral, bytes, List, Dict, ExtraT]
+PSStackType = Union[str, float, bool, PSLiteral, bytes, List, Dict, ExtraT]
 PSStackEntry = Tuple[int, PSStackType[ExtraT]]