TODO:

• [x] Wire up new error struct in lexer2
• [x] Add insta tests for lexing errors
• [x] Start writing parser, copying most of parser.rs probably
  • [x] raw
  • [x] block
  • [x] for loop
  • [x] if/elif/else
  • [x] filter section
  • [x] macro definition
  • [x] macro imports
• [x] Delete logos lexer/tests/parser
• [x] Adds lots of tests, some with insta some without
  • [x] Make sure the spans are always correct
  • [x] Handle all custom errors from previous parser
  • [x] Handle extends not being the first tag as error
  • [x] Handle nodes not allowed in certain places (eg macro def inside a macro def)
• [x] Fuzz a lot
• [x] Polish lexer + parser until it's perfect
• [x] More fuzzing
• [x] Generate bytecode
• [x] Decide where to calculate byte size hint, probably compiler
• [x] Fix blocks/macros AST -> bytecode generation
• [x] Fix macro call weird instruction (idx, idx).
• [x] Have a reasonable Template object (eg macro imports, extend)
• [x] Add support for block assignment in lexer/parser/compiler
• [x] Handle map literals (only allow string as keys for now?)
• [x] More fuzzing
• [x] Add a Context object that holds values like the one in Tera
• [x] Add an escape_html fn with benchmarks and a faster one featured gated
• [x] Add a Tera object that holds all the templates
• [x] Do the equivalent of build_inheritance_chains from v1. Maybe create a new VerifiedTemplate or whatever?
• [ ] Implement basic VM without filters/functions/tests
  • [ ] Port all the corresponding tests from Tera v1 + some more
  • [x] Ensure variables used in {{ }} are defined (vs if/tests where undefined are just falsy?)
  • [x] Fix bytecode generation when it's wrong
  • [x] Allow anything that can be converted to a key as a key for inline maps (eg add bool/integers)
  • [x] Make sure strings are escaped automatically (Value::String could be an enum with safe/unsafe string like markupsafe in python?) when printing
  • [ ] Fix/remove all the TODOs
  • [ ] Improve perf till it's better than Tera v1
  • [x] Iterating on strings should require an optional unic_segment feature for unicode
  • [x] Ensure that errors point to the right thing (<--- that's the long one, but done after perf work)
  • [ ] Finish VM
• [x] Design filters/functions/tests types
• [x] Implement basic builtin filters/functions/tests
• [x] Add filters/functions/tests to VM
• [x] Uncomment all tests using filters/functions/tests
• [x] Parsing errors should report with the source context like Rust errors with the right spans
• [ ] Add more helpful errors when loading templates (eg a forloop with for key, key in value/missing includes etc)
• [ ] Allow escape chars (eg \n) in strings concat, there was an issue about that in Zola
• [ ] Feature to load templates from a glob with optional dep
• [x] MAYBE: add a way to add global context to the Tera struct that are passed on every render automatically
• [ ] Shitload of tests
• [ ] More fuzzing

Ideas:

• Collect all functions/filters/macro call/includes/tests and make sure it's all available at compile time
• Pre-compute hashes for all keys used in the templates somehow? runtime phf? https://crates.io/crates/ph ?
• string interning for Key/Value?
• Pre-render macro calls without arguments?
• Check whether blocks have super() and if they don't just skip them when rendering and they are in the middle of the ancestry
• Have a way to merge chunks when handling inheritance, issue is macros since you need to refer to the right imports
• Collect include templates so we know whether we have all of them or not and error otherwise
• Make raw template keep spans rather String to avoid cloning it?
• Use Arc in Value
• Mark literal strings in templates as safe?

Thoughts on making LoadName error, we can change the semantics from v1 a bit eg:

• {{ hey }} should error if hey is undefined
• {{ existing.hey }} should error if hey is undefined but existing is
• {{ hey or 1 }} should print 1
• {% if hey or true %} should be truthy
• {% if hey.other or true %} should error if hey is not defined (currently truthy)
• {{ hey.other or 1 }} should error if hey is not defined (currently prints "true")

Breaking changes

• {{ falsy or "hello" }} prints "hello" instead of "true"
• {% if not_existing.field %} errors if not_existing is undefined, we only allow one level of undefinedness (hello undefined is not an object)
• include [...] ignore missing has been removed
• trim filters have been merged in trim/trim_start/trim_end with an optional pat argument for start/end rather than separate filters
• int and float filter do not have a default anymore
• round filter does not take a common method anymore, it's the default and should not be filled if needed
• indent filter now takes a width param rather than prefix
• map, group_by and filter filter will error if the attribute ends up being undefined on one of the value
• as_str has been renamed to str
• object test has been renamed map
• filters now always take kwargs