Method getConstLiteral

packages/compiler/src/constant_pool.ts:97–156

(literal: o.Expression, forceShared?: boolean)

  constructor(private readonly isClosureCompilerEnabled: boolean = false) {}

  getConstLiteral(literal: o.Expression, forceShared?: boolean): o.Expression {
    if (
      (literal instanceof o.LiteralExpr && !isLongStringLiteral(literal)) ||
      literal instanceof FixupExpression
    ) {
      // Do no put simple literals into the constant pool or try to produce a constant for a
      // reference to a constant.
      return literal;
    }
    const key = GenericKeyFn.INSTANCE.keyOf(literal);
    let fixup = this.literals.get(key);
    let newValue = false;
    if (!fixup) {
      fixup = new FixupExpression(literal);
      this.literals.set(key, fixup);
      newValue = true;
    }

    if ((!newValue && !fixup.shared) || (newValue && forceShared)) {
      // Replace the expression with a variable
      const name = this.freshName();
      let value: o.Expression;
      let usage: o.Expression;
      if (this.isClosureCompilerEnabled && isLongStringLiteral(literal)) {
        // For string literals, Closure will **always** inline the string at
        // **all** usages, duplicating it each time. For large strings, this
        // unnecessarily bloats bundle size. To work around this restriction, we
        // wrap the string in a function, and call that function for each usage.
        // This tricks Closure into using inline logic for functions instead of
        // string literals. Function calls are only inlined if the body is small
        // enough to be worth it. By doing this, very large strings will be
        // shared across multiple usages, rather than duplicating the string at
        // each usage site.
        //
        // const myStr = function() { return "very very very long string"; };
        // const usage1 = myStr();
        // const usage2 = myStr();
        value = new o.FunctionExpr(
          [], // Params.
          [
            // Statements.
            new o.ReturnStatement(literal),
          ],
        );
        usage = o.variable(name).callFn([]);
      } else {
        // Just declare and use the variable directly, without a function call
        // indirection. This saves a few bytes and avoids an unnecessary call.
        value = literal;
        usage = o.variable(name);
      }

      this.statements.push(
        new o.DeclareVarStmt(name, value, o.INFERRED_TYPE, o.StmtModifier.Final),
      );
      fixup.fixup(usage);
    }