## Suggestion: Add fancier trace debugging functions to `Hasura.Prelude`
This PR adds two trace functions, `ltrace` and `ltraceM`, which use the `pretty-simple` package to `show` the input with nice formatting and colors for ease of reading (and comparing using diff tools such as `meld` or `vim-diff`).
I've also added warning pragmas to the functions, which means:
1. Traces will not be left in code, as CI builds with -Werror
2. Developers will have to change the `ghc-options` to `-Wwarn` in their `cabal.project.local` settings to use these functions
### Example
Usage:
```hs
selectFunctionAggregate ... = ... do
ltraceM "functionInfo" function
...
```
Output to terminal looks like this:
<img width="524" alt="Screen Shot 2021-08-12 at 10 33 24" src="https://user-images.githubusercontent.com/8547573/129158878-4a5e96ba-30a5-452c-8f33-9eb4b2cc5e2a.png">
### Dependencies
Requires adding the following dependencies:
- prettyprinter-ansi-terminal-1.1.2 (BSD2)
- pretty-simple-4.0.0.0 (BSD3)
Question: what is the process for adding new dependencies? How does decisions on this matter happen?
https://github.com/hasura/graphql-engine-mono/pull/2075
GitOrigin-RevId: 490b0f0ca595da319b43e92e190ba50c0b132cd5
>
### Description
>
From HGE version 2.0 onwards, all remote relationship fields are generated as plain types without non-nullable and lists. This PR fixes the same.
### Changelog
- [x] `CHANGELOG.md` is updated with user-facing content relevant to this PR. If no changelog is required, then add the `no-changelog-required` label.
### Affected components
- [x] Server
- [x] Tests
### Related Issues
->
fix https://github.com/hasura/graphql-engine/issues/7284
### Steps to test and verify
>
- Create a remote relationship to a field in remote schema with non-nullable or list type
- The HGE introspection should give the remote relationship field type correctly as like in the remote schema
https://github.com/hasura/graphql-engine-mono/pull/2071
GitOrigin-RevId: e113f5d17b62bfa0a25028c20260ae1782ae224b
This PR adds source code documentation for metadata versioning.
Note: Adding `force-skip-ci` label to bypass server tests as this PR only has changes in source code comments.
https://github.com/hasura/graphql-engine-mono/pull/2026
GitOrigin-RevId: f24dcc1579f98e59e40677b99890a8af273bb96e
### A long tale about encoding
GraphQL has an [introspection system](http://spec.graphql.org/June2018/#sec-Introspection), which allows its schema to be introspected. This is what we use to introspect [remote schemas](41383e1f88/server/src-rsr/introspection.json). There is one place in the introspection where we might find GraphQL values: the default value of an argument.
```json
{
"fields": [
{
"name": "echo",
"args": [
{
"name": "msg",
"defaultValue": "\"Hello\\nWorld!\""
}
]
}
]
}
```
Note that GraphQL's introspection is transport agnostic: the default value isn't returned as a JSON value, but as a _string-encoded GraphQL Value_. In this case, the value is the GraphQL String `"Hello\nWorld!"`. Embedded into a string, it is encoded as: `"\"Hello\\nWorld!\""`.
When we [parse that value](41383e1f88/server/src-lib/Hasura/GraphQL/RemoteServer.hs (L351)), we first extract that JSON string, to get its content, `"Hello\nWorld!"`, then use our [GraphQL Parser library](21c1ddfb41/src/Language/GraphQL/Draft/Parser.hs (L200)) to interpret this: we find the double quote, understand that the content is a String, unescape the backslashes, and end up with the desired string value: `['H', 'e', 'l', 'l', 'o', '\n', 'W', 'o', 'r', 'l', 'd', '!']`. This all works fine.
However, there was a bug in the _printer_ part of our parser library: when printing back a String value, we would not re-escape characters properly. In practice, this meant that the GraphQL String `"Hello\nWorld"` would be encoded in JSON as `"\"Hello\nWorld!\""`. Note how the `\n` is not properly double-escaped. This led to a variety of problems, as described in #1965:
- we would successfully parse a remote schema containing such characters in its default values, but then would print those erroneous JSON values in our introspection, which would _crash the console_
- we would inject those default values in queries sent to remote schemas, and print them wrong doing so, sending invalid values to remote schemas and getting errors in result
It turns out that this bug had been lurking in the code for a long time: I combed through the history of [the parser library](https://github.com/hasura/graphql-parser-hs), and as far as I can tell, this bug has always been there. So why was it never caught? After all, we do have [round trip tests](21c1ddfb41/test/Spec.hs (L52)) that print + parse arbitrary values and check that we get the same value as a result. They do use any arbitrary unicode character in their generated strings. So... that should have covered it, right?
Well... it turns out that [the tests were ignoring errors](7678066c49/test/Spec.hs (L45)), and would always return "SUCCESS" in CI, even if they failed... Furthermore, the sample size was small enough that, most of the time, _they would not hit such characters_. Running the tests locally on a loop, I only got errors ~10% of the time...
This was all fixed in hasura/graphql-parser-hs#44. This was probably one of Hasura's longest standing bugs? ^^'
### Description
This PR bumps the version of graphql-parser-hs in the engine, and switches some of our own arbitrary tests to use unicode characters in text rather than alphanumeric values. It turns out those tests were much better at hitting "bad" values, and that they consistently failed when generating arbitrary unicode characters.
https://github.com/hasura/graphql-engine-mono/pull/2031
GitOrigin-RevId: 54fa48270386a67336e5544351691619e0684559
### Description
A first PR, #1947, removed all the `Arbitrary` stuff from our codebase. But #1740, merged on the same day, added some tests relying on `Arbitrary`. In the merge process, some unneeded `Arbitrary` code got reintroduced.
This PR removes all `Arbitrary` stuff from `src-lib`, and cleans / refactor `Hasura.Generator` in `src-test` to only reduce it to the bare minimum amount of `Arbitrary` instances.
https://github.com/hasura/graphql-engine-mono/pull/1957
GitOrigin-RevId: 7e76009bb022205e3737fca45749411a266cc08c
The `LazyTxT` type was introduced to avoid connecting to Postgres when a given GraphQL request did not require this. However, through the new way query execution plans are represented, this has now _mostly_ been taken care of in a different way, and so no `LazyTxT` action is generated at all for GraphQL requests that do not fetch data from Postgres.
This removes the laziness of `LazyTxT` by simply making it a newtype wrapper around `Q.TxET`. This simplifies a lot of code in `Hasura.Backends.Postgres.Connection`.
https://github.com/hasura/graphql-engine-mono/pull/1959
GitOrigin-RevId: 58b4d5a05d67bc602b59e02ac338f1c3e63859c7
This PR:
- removes a dependency on Postgres' `ToSQL` in other backends
- removes some usage of `unsafePerformIO` in `FronJSON` / `Arbitrary`
- fixes a `Set` into a `HashSet`
- moves some orphan instances where they belong:
- alongside others in `Hasura.Incremental` for `Cacheable`
- in `Hasura.Base.Instances` for `Hashable`
- introduces a local wrapper around ByteString to avoid unsound UTF8 instances
Some of the weird empty lines come from the fact that this PR is an offshoot of #1947.
https://github.com/hasura/graphql-engine-mono/pull/1949
GitOrigin-RevId: ef9d34452946f8466878d8fdda857b0b43816de7
## Description
This PR removes as many constraints as possible from Backend without refactoring the code. Thanks to #1844, a few ToJSON functions can be removed from the IR, and several constraints were simply redundant.
This PR borrows from similar work done as part of #1666.
## Note
To remove constraints more aggressively, I have explored the possibility of _removing Representable altogether_, in a [separate commit](https://github.com/hasura/graphql-engine-mono/compare/nicuveo/remove-extension-constraints..nicuveo/tentative-remove-representable). I am not convinced it's a good idea in terms of readability of the code, but it's a possibility.
Further work includes deciding what we want to do with `Show` and `ToTxt`; see #1747.
https://github.com/hasura/graphql-engine-mono/pull/1843
GitOrigin-RevId: 337324ad90cb8f86f06e1c5a36aa44bb414e195a
Query plan caching was introduced by - I believe - hasura/graphql-engine#1934 in order to reduce the query response latency. During the development of PDV in hasura/graphql-engine#4111, it was found out that the new architecture (for which query plan caching wasn't implemented) performed comparably to the pre-PDV architecture with caching. Hence, it was decided to leave query plan caching until some day in the future when it was deemed necessary.
Well, we're in the future now, and there still isn't a convincing argument for query plan caching. So the time has come to remove some references to query plan caching from the codebase. For the most part, any code being removed would probably not be very well suited to the post-PDV architecture of query execution, so arguably not much is lost.
Apart from simplifying the code, this PR will contribute towards making the GraphQL schema generation more modular, testable, and easier to profile. I'd like to eventually work towards a situation in which it's easy to generate a GraphQL schema parser *in isolation*, without being connected to a database, and then parse a GraphQL query *in isolation*, without even listening any HTTP port. It is important that both of these operations can be examined in detail, and in isolation, since they are two major performance bottlenecks, as well as phases where many important upcoming features hook into.
Implementation
The following have been removed:
- The entirety of `server/src-lib/Hasura/GraphQL/Execute/Plan.hs`
- The core phases of query parsing and execution no longer have any references to query plan caching. Note that this is not to be confused with query *response* caching, which is not affected by this PR. This includes removal of the types:
- - `Opaque`, which is replaced by a tuple. Note that the old implementation was broken and did not adequately hide the constructors.
- - `QueryReusability` (and the `markNotReusable` method). Notably, the implementation of the `ParseT` monad now consists of two, rather than three, monad transformers.
- Cache-related tests (in `server/src-test/Hasura/CacheBoundedSpec.hs`) have been removed .
- References to query plan caching in the documentation.
- The `planCacheOptions` in the `TenantConfig` type class was removed. However, during parsing, unrecognized fields in the YAML config get ignored, so this does not cause a breaking change. (Confirmed manually, as well as in consultation with @sordina.)
- The metrics no longer send cache hit/miss messages.
There are a few places in which one can still find references to query plan caching:
- We still accept the `--query-plan-cache-size` command-line option for backwards compatibility. The `HASURA_QUERY_PLAN_CACHE_SIZE` environment variable is not read.
https://github.com/hasura/graphql-engine-mono/pull/1815
GitOrigin-RevId: 17d92b254ec093c62a7dfeec478658ede0813eb7
