Merge pull request lcompilers#624 from akshanshbhatt/fstring

[Parser] Add support for parsing prefixed strings

src/lpython/parser/parser.yy

@@ -683,6 +683,8 @@ function_call
 string
     : string TK_STRING { $$ = STRING2($1, $2, @$); } // TODO
     | TK_STRING { $$ = STRING1($1, @$); }
+    | id TK_STRING { $$ = STRING3($1, $2, @$); }
+    ;
 
 expr
     : id { $$ = $1; }

src/lpython/parser/semantics.h

@@ -429,10 +429,62 @@ char* concat_string(Allocator &al, ast_t *a, char *b) {
 #define INTEGER(x, l) make_ConstantInt_t(p.m_a, l, x, nullptr)
 #define STRING1(x, l) make_ConstantStr_t(p.m_a, l, x.c_str(p.m_a), nullptr)
 #define STRING2(x, y, l) make_ConstantStr_t(p.m_a, l, concat_string(p.m_a, x, y.c_str(p.m_a)), nullptr)
+#define STRING3(id, x, l) PREFIX_STRING(p.m_a, l, name2char(id), x.c_str(p.m_a))
 #define FLOAT(x, l) make_ConstantFloat_t(p.m_a, l, x, nullptr)
 #define COMPLEX(x, l) make_ConstantComplex_t(p.m_a, l, 0, x, nullptr)
 #define BOOL(x, l) make_ConstantBool_t(p.m_a, l, x, nullptr)
 
+static inline ast_t *PREFIX_STRING(Allocator &al, Location &l, char *prefix, char *s){
+    Vec<expr_t *> exprs;
+    exprs.reserve(al, 4);
+    ast_t *tmp;
+    if (strcmp(prefix, "f") == 0) {
+        std::string str = std::string(s);
+        std::string s1 = "\"";
+        std::string id;
+        std::vector<std::string> strs;
+        bool open_paren = false;
+        for (size_t i = 0; i < str.length(); i++) {
+            if(str[i] == '{') {
+                if(s1 != "\"") {
+                    s1.push_back('"');
+                    strs.push_back(s1);
+                    s1 = "\"";
+                }
+                open_paren = true;
+            } else if (str[i] != '}' && open_paren) {
+                id.push_back(s[i]);
+            } else if (str[i] == '}') {
+                if(id != "") {
+                    strs.push_back(id);
+                    id = "";
+                }
+                open_paren = false;
+            } else if (!open_paren) {
+                s1.push_back(s[i]);
+            }
+            if(i == str.length()-1 && s1 != "\"") {
+                s1.push_back('"');
+                strs.push_back(s1);
+            }
+        }
+
+        for (size_t i = 0; i < strs.size(); i++) {
+            if (strs[i][0] == '"') {
+                strs[i] = strs[i].substr(1, strs[i].length() - 2);
+                tmp = make_ConstantStr_t(al, l, LFortran::s2c(al, strs[i]), nullptr);
+                exprs.push_back(al, down_cast<expr_t>(tmp));
+            } else {
+                tmp = make_Name_t(al, l,
+                        LFortran::s2c(al, strs[i]), expr_contextType::Load);
+                tmp = make_FormattedValue_t(al, l, EXPR(tmp), -1, nullptr);
+                exprs.push_back(al, down_cast<expr_t>(tmp));
+            }
+        }
+    }
+    return make_JoinedStr_t(al, l, exprs.p, exprs.size());
+}
+
 static inline keyword_t *CALL_KW(Allocator &al, Location &l,
         char *arg, expr_t* val) {
     keyword_t *r = al.allocate<keyword_t>();

tests/parser/string1.py

@@ -0,0 +1,7 @@
+f"Hello, {first_name} {last_name}. You are {age} years old."
+
+print(f"{__file__} executed in {elapsed} seconds.")
+
+# TODO: Support format specifiers
+
+# print(f"{__file__} executed in {elapsed:0.2f} seconds.")

tests/reference/ast_new-string1-96b90b3.json

@@ -0,0 +1,13 @@
+{
+    "basename": "ast_new-string1-96b90b3",
+    "cmd": "lpython --show-ast --new-parser --no-color {infile} -o {outfile}",
+    "infile": "tests/parser/string1.py",
+    "infile_hash": "e51ab7a60ad39354a13d987f0ed3bdb8f51b8e6d2a677a9d7b720749",
+    "outfile": null,
+    "outfile_hash": null,
+    "stdout": "ast_new-string1-96b90b3.stdout",
+    "stdout_hash": "00a9b4899bd6ba7938b503da224840f51e2e7ba2e41121292809bdf2",
+    "stderr": null,
+    "stderr_hash": null,
+    "returncode": 0
+}

tests/reference/ast_new-string1-96b90b3.stdout

@@ -0,0 +1 @@
+(Module [(Expr (JoinedStr [(ConstantStr "Hello, " ()) (FormattedValue (Name first_name Load) -1 ()) (ConstantStr " " ()) (FormattedValue (Name last_name Load) -1 ()) (ConstantStr ". You are " ()) (FormattedValue (Name age Load) -1 ()) (ConstantStr " years old." ())])) (Expr (Call (Name print Load) [(JoinedStr [(FormattedValue (Name __file__ Load) -1 ()) (ConstantStr " executed in " ()) (FormattedValue (Name elapsed Load) -1 ()) (ConstantStr " seconds." ())])] []))] [])

tests/tests.toml

@@ -384,6 +384,10 @@ ast_new = true
 filename = "parser/while1.py"
 ast_new = true
 
+[[test]]
+filename = "parser/string1.py"
+ast_new = true
+
 # tests/errors
 
 [[test]]