Inja bump from 2.1 -> 3.4

[jbohanon]

The following is a curated enumeration of the functional changes to the Inja library as we consume it when upgrading from v2.1 to v3.4. This is to track the work required to support solo-io/gloo#8177

2.2

• ✔️ [CHANGE] Environment() constructor changed to use empty string instead of "./". link
  • ensure we aren't calling naked Environment() anywhere
  • this change was reverted in 3.4
• [FEATURE] added at function to access elements in an array by index link
  • index out of range?
• ✔️ [CHANGE] Environment's load_json will throw exception if file not found link
  • trace codepaths that use this and ensure we aren't using any
• [FEATURE] add whitespace control options trim_blocks and lstrip_block link jinja reference
• [FEATURE] a template can be included inside a loop, retaining the parent context link
• ✔️ [CHANGE] Environment's Impl class removed link
  • ensure we aren't using this piece of Environment

3.0

• ✔️ [CHANGE] Reworked exception throwing link
  • ensure we're not relying on the format of exceptions thrown out of inja; update accordingly
• [FEATURE] Loop features index, index1, is_first, is_last can be used when looping over objects (maps) link
• [PERFORMANCE] Improved performance when looping over large datasets link
• ✔️ [CHANGE] removal of polyfill; not sure what was being polyfilled link
  • ensure we build without this
• [FEATURE] disable searching for templates on file system link
  • New field in ParserConfig
  • Expose or explicitly enable depending on how we currently allow template configuration
• [FEATURE] disable throwing an exception if included template not found link
  • New struct RenderConfig
  • Expose?
  • Test envoy behavior with/without setting with missing include
• [FEATURE] add fine-grained whitespace control for statements e.g. {%+, {%-, -%} link
• ✔️ [CHANGE] Node constructor signatures all changed to require size_t argument link
  • ensure we are not calling this constructor anywhere
• ✔️ [CHANGE] Major rewrite of core (AKA the big one) link
  • Parser constructor now take 4 args instead of 3
    • 4th argument function_storage...
  • Pointer element notation removed from Parser config JSON Pointer RFC
    • test Envoy behavior if templates use pointer notation
    • explore possibly translating JSON pointers as a stopgap
• [FEATURE] Plus, minus, times, slash, percent, power tokens added
  • test these operations for common errors, validate envoy behavior if failure
    • e.g. divide by zero, operations on NaN tokens
• ✔️ [CHANGE] Numerous methods in Parser and Renderer made private link
  • ensure we build with this
• [FEATURE] exists operation extended to be able to safely chain json pointers link
  • e.g. exists("array.1.name") can be used instead of the multiple calls exists("array"), existsIn("1", array), and existsIn("name", array.1)
• [FEATURE] AtId operation added to access specific elements in a list of objects link
• [PERFORMANCE] strings are no longer copied around needlessly link

3.1

• [FEATURE] Add set statement to mutate data link
  • verify this only affects current scope and all child scopes; not parent scope
• ✔️ [CHANGE] numerous values changed to const link
  • verify we build with this
• [FEATURE] Add void callback link
  • we could use for logging or mutating dynamic metadata or modifying stats
• [FEATURE] add fine-grained whitespace control for expressions e.g. {{%-, -%}} link
• [FEATURE] consume UTF-8 byte order mark (BOM) link
  • this will not affect us

3.2

• [FEATURE] Allow variables starting with @ and $ link
• [FEATURE] Inja can be configured to abort instead of throw link

3.3

• [CHANGE] short-circuit evaluation link
  • We need to add documentation around this. test case link
• [FEATURE] inheritance between templates link
  • we should add extensive testing around this in case users build mega-templates with multiple levels of inheritence
• [FEATURE] set statements can access child data via dot notation (not pointer notation as the docs state) link
• [FEATURE] add fine-grained whitespace control for comments e.g. {#-, -#} link
• [FEATURE] at can be nested to dynamically access object fields link
  • see test case for usage
• [FEATURE] join function added to join lists with a separator link

3.4

• [FEATURE] include callback link
  • this should be of limited use to us since we do not include from filesystem
• ✔️ [CHANGE] Environment fields input_path and output_path changed from Public to Protected link
  • ensure we build with this
• ✔️ [CHANGE] Environment() constructor changed to use "./" instead of empty string link
  • this is a reversion of a change in 2.2, no action should be required
• [CHANGE] passing too few arguments to a function throws a parser error link
  • test envoy behavior when this error is thrown

Tasks

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1. Build issues
2. Tests for potential breaks
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