nic-6443 commented on issue #12932:
URL: https://github.com/apache/apisix/issues/12932#issuecomment-4221987929
## Analysis: Root Cause and Proposed Fix
### Root Cause
The current `resolve_conf_var()` in `apisix/cli/file.lua` does env var
substitution **after** YAML parsing (table-level). At that point, YAML quoting
context is lost — both `"${{VAR}}"` (quoted) and `${{VAR}}` (unquoted) become
the same Lua string `"${{VAR}}"`. The code then blindly applies `tonumber()` to
all substituted values, which:
1. **Breaks string-typed fields** — `client_id: "${{VAR}}"` with `VAR=12345`
becomes number `12345`, failing schema validation (expects string). This
affects ANY numeric value, not just large ones.
2. **Loses precision for large numbers** — `VAR=356002209726529540` →
`3.5600220972653e+17`.
3. **Gives users no way to control types** — YAML quotes (the standard
mechanism) are ignored.
### Why PR #13078 Does Not Fix This
The `exceeds_lua_precision()` check (skip `tonumber()` for integers >15
digits) only addresses symptom (2). Short numeric strings like `VAR=12345` in
string-typed fields are still incorrectly converted. The fundamental problem
remains: **type conversion is schema-agnostic and happens after YAML type
context is lost**.
### Proposed Fix: Text-Level Substitution Before YAML Parsing
Move `${{VAR}}` substitution from **post-parse** (on the Lua table) to
**pre-parse** (on the raw YAML text), for `apisix.yaml` only. This lets YAML's
native type rules handle everything correctly:
```yaml
client_id: "${{VAR}}" # VAR=12345 → client_id: "12345" → string ✓
retries: ${{RETRIES}} # RETRIES=3 → retries: 3 → number ✓
http_to_https: ${{FLAG}} # FLAG=true → http_to_https: true → boolean ✓
node_weight: ${{WEIGHT}} # WEIGHT=1 → node_weight: 1 → number ✓
client_id: "${{VAR}}" # VAR=356...0 → client_id: "356...0" → string ✓
```
Users control types through standard YAML quoting — quoted = string,
unquoted = YAML-inferred type. This is the same approach used by Helm,
envsubst, and other template tools.
**Scope**: Only `apisix.yaml` in standalone mode (both CLI init and runtime
reload). `config.yaml` keeps the current table-level substitution unchanged
(backward compatible).
**Cost**: ~25 lines for a new `resolve_yaml_text_var()` function (same regex
as existing `var_sub`), 2 call sites updated. Low risk, minimal code change.
**Known considerations** (consistent with Helm/envsubst behavior):
- Env var values containing YAML special characters (`"`, `\n`, `:`) must be
used in appropriate YAML quoting context
- Commented-out `${{VAR}}` patterns will be processed (unlike table-level
where comments are stripped by YAML parser first)
- Full YAML implicit typing applies to unquoted substituted values (e.g.,
`on`/`off`/`null`)
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