Clean up unnecessary usage of String type in favour of Text

[Purplegaze]

Proposed Changes

Removes unnecessary uses of Data.Text.pack and simplifies code to avoid usage of the String type to account for the OverloadedStrings compiler extension.

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Questions and Comments

Will post in a separate comment below.

[Purplegaze]

CourseControllerTests, IntersectionTests, Config: removed T.pack for string literals.
Svg/Parser: Used T.splitOn instead of List.splitOn to avoid converting to String type.

The remaining String to Text conversions fall into these categories:

1. Usage of show (appears several times, e.g. DynamicGraphs/WriteRunDot.hs, Export/TimetableImageCreator.hs, Svg/Builder.hs)
   • It looks like the external package text-show provides a Text equivalent of the Show typeclass, which I could try importing if this is a worthwhile change.
2. Usage of String within the local Req datatype
   • Changing this datatype to use Text instead of String sounds quite breaking, considering the wide variety of functions it's used in.
3. String type used within Parsec parsers (e.g. parseCourseTitle in WebParsing/ArtSciParser.hs)
   • These constructions iterate through characters one at a time by design, so somehow rewriting them using Text sounds like it'd be unnatural and wouldn't provide much performance benefit.

Would like a follow-up on whether you think any of these categories should also be simplified, or if the current changes are enough.

Side question: what's the easiest way to test whether the Svg/Parser changes work as expected? Should I try to write tests for this file, since I've altered it and it doesn't have any, or are these tangentially tested somewhere else?

[coveralls]

Pull Request Test Coverage Report for Build 573f628e-7148-48ae-918f-aa3f439e1370

Details

• 6 of 10 (60.0%) changed or added relevant lines in 4 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 56.41%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
app/Config.hs	0	1	0.0%
app/Export/TimetableImageCreator.hs	0	1	0.0%
app/Svg/Builder.hs	3	5	60.0%

Totals
Change from base Build 23a74828-109c-43b3-a396-9b446ca521b1:	0.0%
Covered Lines:	2280
Relevant Lines:	3968

---

💛 - Coveralls

[Purplegaze]

(see comment above, not sure if I should have pressed "request review" instead of sending a Slack message yesterday)

[david-yz-liu]

Hi @Purplegaze, thanks for making this PR! Sending a message on Slack was fine, but so was requesting a review (either is an acceptable way to flag an in-progress PR to my attention).

Regarding your notes about the remaining String instances: you can add the text-show package to our dependencies, that's a nice find. Don't worry about changing the Req datatype or the Parsec parsers for this PR.

You're right that there aren't tests currently for the Svg.Parser module. Don't worry about adding test cases for them here, but you can test your changes manually by re-running the database-graphs command.

[Purplegaze]

Thanks! Should be ready for review now.

[david-yz-liu]

Nice work, @Purplegaze!